Designing property drainage systems

Designing property drainage systems
CPCPDR3021A CPCPSN3022A TAFE QUEENSLAND GOLD COAST

TAFE QUEENSLAND GOLD COAST
Resources required AS3500.2:2003 Sanitary plumbing and drainage. AS3500.0:2003 Glossary of terms. Student resource book – Designing property drainage systems. TAFE QUEENSLAND GOLD COAST

Outcomes At the completion of this lesson students will have a sound knowledge of the correct procedure to install sanitary drainage systems to AS3500. TAFE QUEENSLAND GOLD COAST

What is a property drain?
AS3500.0:2003 Glossary of terms Sewer – A conduit for the carriage of sewerage. (page 44) Sewage – The waste water from the community, including all faecal matter, urine, household and commercial waste water that contains human waste. (page 43) TAFE QUEENSLAND GOLD COAST

Sewerage system – A system that includes all sewer and sewerage works. (page 44) Drain Sanitary – A line of pipes above or below ground within the property boundary, including all fittings and equipment generally external to a building, intended to convey, under gravity, sewage or trade waste. (page 15) TAFE QUEENSLAND GOLD COAST

Point of connection (sewer) – The point provided for the connection of a property sanitary drain by the authority’s sewer. TAFE QUEENSLAND GOLD COAST

Sewer main systems. Boundary trap areas What is a boundary trap? AS3500.0:2003 Glossary of terms A trap used to aerially disconnect the house drain from the sewer. (page 55) TAFE QUEENSLAND GOLD COAST

Sewer mains installed in the older parts of Australian cities require boundary traps to be used as the method of connection between the property drain and the sewer. TAFE QUEENSLAND GOLD COAST

The purpose of a boundary trap is to provide a water seal to prevent the flow of sewer gasses from the authority’s reticulated sewer main to the property drain. The water seal of the boundary trap acts as a barrier to the gasses TAFE QUEENSLAND GOLD COAST

The boundary trap must be at least 100 mm in size and of a ‘P’ trap form with a minimum of 50 mm of water seal. It must be placed within the property as close as practicable to the sewer connection point, in an accessible position and clear of any easement TAFE QUEENSLAND GOLD COAST

The design of boundary traps manufactured in PVC has been modified to facilitate passage of TV camera’s and drain cleaning equipment through the trap and outlet bend sections. TAFE QUEENSLAND GOLD COAST

AS3500.2:2003 Sanitary plumbing and drainage - contents.
SECTION 4 DRAINAGE SYSTEM 4.1 SCOPE OF SECTION 4.2 POINT OF CONNECTION 4.3 DRAINS 4.4 INSPECTION SHAFTS AND BOUNDARY TRAPS 36 4.5 REFLUX VALVES 4.6 GULLIES 4.7 INSPECTION OPENINGS (IO) 4.8 INSPECTION CHAMBERS 4.9 JUNCTIONS IN DRAINS 4.10 JUMP-UPS 4.11 DISCONNECTION AND SEALING TAFE QUEENSLAND GOLD COAST

4.4.4 Installation of boundary traps
Outside buildings Boundary traps located outside buildings shall be installed in accordance with the following: Where the point of connection is provided in a vertical section of the sewer within the property, a boundary trap shall not be installed in the same trench as the sewer jumpup. A downstream vent complying with Clause shall be installed at the boundary trap riser. TAFE QUEENSLAND GOLD COAST

Boundary traps of materials, other than cast iron, shall be directly supported on a solid foundation by placing under the trap a concrete pad that shall— (i) be not less than 100 mm thick; and (ii) extend upwards to the inlet socket of the trap. The shaft shall be protected and supported during the installation and placement of backfilling. TAFE QUEENSLAND GOLD COAST

Inside buildings Boundary traps located inside buildings and installed above the ground or floor surface shall be— protected against mechanical damage; located as close as practicable to and within the boundary line; and supported independently of the drain. TAFE QUEENSLAND GOLD COAST

Size The size of the boundary traps and risers shall be not smaller in size than the drain that discharges to it, or smaller than DN 100. TAFE QUEENSLAND GOLD COAST

4.4 INSPECTION SHAFTS AND BOUNDARY TRAPS
4.4.1 General The main drain shall be provided with either an inspection shaft in non-boundary trap areas, or a boundary trap in boundary trap areas, located at or near the point of connection to the sewer. Inspection shafts and boundary traps located in an area that is subject to flooding shall comply with the requirements of the relevant authority. TAFE QUEENSLAND GOLD COAST

Installation The inspection shafts and boundary trap risers shall comply with the following: (a) They shall terminate at or near ground or surface level with a removable airtight inspection cap of the same diameter as the shaft or riser. In the case of boundary trap risers a low level vent shall be installed in accordance with Clause (b) The cap shall be suitably sealed into the shaft or riser. TAFE QUEENSLAND GOLD COAST

(c) Where the inspection shaft or boundary trap riser is likely to be damaged by vehicular traffic, the cap may be installed below surface level. Access shall be provided in accordance with the following: (i) A heavy-duty trafficable cover shall be installed at surface level above and independent of the cap. (ii) The cover shall be suitably supported so that no load can be transmitted onto the shaft. (iii) The shaft shall be terminated just below the underside of the cover. TAFE QUEENSLAND GOLD COAST

Location The inspection shaft or boundary trap riser shall be located— (a) wholly within the property served; (b) as close as practicable to the boundary; (c) clear of all authority easements; TAFE QUEENSLAND GOLD COAST

(d) as near as practicable to the point of connection; (e) in the open air, except as provided in Clause ; (f) in an accessible position; and (g) so that the inspection cap is not covered from view, except as allowed in Clause (c). TAFE QUEENSLAND GOLD COAST

4.4.2.3 Alternative locations
Where the requirements of Clause cannot be met, an inspection shaft and boundary trap riser may be sited at other locations as follows: (a) Under cover An inspection cap may be installed under a roofed area. The cap shall— be located at floor or ground level; and be readily accessible for inspection, rodding and plunging with not less than 1 m clear space vertically above the inspection cap. TAFE QUEENSLAND GOLD COAST

(b) In a recess If all or part of a building is constructed up to the boundary of the property, and if this makes it impracticable to site the inspection cap in the open air or within a building under cover, the inspection cap may be installed within a recess constructed in the wall of the building, providing the following requirements are met: The inspection cap shall be airtight. TAFE QUEENSLAND GOLD COAST

The recess shall be constructed to provide a clear space of at least 1 m above the inspection cap. At least 100 mm clear space shall be provided on each side and to the rear of the inspection cap. The recess shall have a removable panel TAFE QUEENSLAND GOLD COAST

Sewer main systems. Inspection shaft (boundary trap omitted) What is an inspection shaft? AS3500.0:2003 Glossary of terms A shaft constructed in the line of a sanitary drain for the purpose of inspection and future access for locating and clearing the drain. (page 26) TAFE QUEENSLAND GOLD COAST

In a non-boundary trap area, the sewer gasses from the reticulated sewer are allowed to pass into the house drain and out of the drainage vent. In this situation, property drainage vents ventilate the authority’s reticulated drain as well as the house drain. TAFE QUEENSLAND GOLD COAST

On every property drain where a boundary trap is not required by the sewerage authority, an inspection shaft must be placed within the property as close as practicable to the sewer connection point, in an accessible position and clear of any easement. The inspection shaft is used to check for blockages in the system and testing purposes. TAFE QUEENSLAND GOLD COAST

4.4.3 Installation of inspection shafts
General Inspection shafts shall be provided at the lower downstream end of a drain in accordance with the following: (a) A junction shall be installed in the graded drain with the branch of the junction extended vertically upwards to the surface to form a shaft. TAFE QUEENSLAND GOLD COAST

(b) Where a jump-up is constructed within a property and is not more than 3 m from the point of connection, the jump-up shall be extended upwards to the surface level to form a shaft. (c) No branch drain or fixture discharge pipe shall be connected to an inspection shaft where the shaft is constructed from a square junction installed in a graded drain. TAFE QUEENSLAND GOLD COAST

(d)The jump-up shall be supported by placing a concrete footing not less than 100 mm thick under the bend, with a width of not less than 100 mm beyond the sides of the shaft, and extending up to the centre-line of the drain. An inspection chamber with an open channel or maintenance shaft in accordance with AS/NZS 4999 may take the place of an inspection shaft. TAFE QUEENSLAND GOLD COAST

Size Inspection shafts shall be— the same size as the drain for drains up to DN 150; not smaller than DN 150 for drains larger than DN 150; or the same size as the jump-up where an inspection shaft is constructed by extending a jump-up. TAFE QUEENSLAND GOLD COAST

What is surcharge protection?
AS3500.0:2003 Glossary of terms Surcharge (sanitary) – Overflow from a sewer or combined sewer caused by overloading, or chokage. Usually used in reference to wet weather infiltration or inflow. (page 51) TAFE QUEENSLAND GOLD COAST

Authorities’ sewer mains may surcharge (overflow) due to blockages, sewer collapse or the infiltration of storm water into the sewer system. This overflow can enter the drains of all the properties connected to the sewer in locations upstream of the surcharge problem. TAFE QUEENSLAND GOLD COAST

Property drains need protection from the effects of surcharge to ensure there is no chance of the overflow occurring inside buildings connected to the sewer. An internal overflow could lead to health risk to the occupants, and internal damage to buildings. TAFE QUEENSLAND GOLD COAST

Types of surcharge protection
Overflow relief gully (ORG) AS3500.0:2003 Glossary of terms Overflow (relief) gully – A self cleansing trap, provided with a suitable loosely fitted grating located above ground surface level, provided for the relief of any possible surcharge and to provide a measure of protection against overflow from a drain.(page23) TAFE QUEENSLAND GOLD COAST

A disconnector gully assembly is used as an overflow point on most drainage installations. When used for this purpose, the disconnector gully assembly is known as an ‘Overflow Relief Gully’ (ORG). The gully must be fitted with a grating that pops up to allow unrestricted flow in the event of surcharge. TAFE QUEENSLAND GOLD COAST

AS3500.2:2003 Sanitary plumbing and drainage - contents.
SECTION 4 DRAINAGE SYSTEM 4.1 SCOPE OF SECTION 4.2 POINT OF CONNECTION 4.3 DRAINS 4.4 INSPECTION SHAFTS AND BOUNDARY TRAPS 36 4.5 REFLUX VALVES 4.6 GULLIES 4.7 INSPECTION OPENINGS (IO) 4.8 INSPECTION CHAMBERS 4.9 JUNCTIONS IN DRAINS 4.10 JUMP-UPS 4.11 DISCONNECTION AND SEALING TAFE QUEENSLAND GOLD COAST

4.6.6 Overflow relief gullies
General At least one overflow relief gully shall be installed in the drain except as provided in Clause Disconnector gullies complying with the requirements of Clauses to may be used as overflow relief gullies. For multi-unit developments, see Section 12. TAFE QUEENSLAND GOLD COAST

Permitted omission An overflow relief gully may be omitted where — (a) the drain serves fixtures in a separate toilet block or an amenities building, which is owned or maintained by a council or similar authority, and is located in a park or reserve, provided that the floor of the building is graded to fall towards an external doorway; TAFE QUEENSLAND GOLD COAST

(b) the site is entirely built on and it is not possible to locate the gully in any of the alternative locations specified in Clause , and the fixtures on the ground floor discharge through a reflux valve to the sewer by gravitation; or (c) the lowest fixtures connected are located on floor levels that are 3 m or more above ground surface level at the point of connection to the sewer. TAFE QUEENSLAND GOLD COAST

Size The size of overflow relief gullies shall be determined from the size of the largest section of the main drain as given in Table 4.2. TABLE 4.2 SIZE OF OVERFLOW RELIEF GULLIES Size of main drain Size of gully outlet 100 and > TAFE QUEENSLAND GOLD COAST

Location Location The overflow relief gully shall be located— (a) within the boundaries of the property; (b) external to the building; (c) so that the top of the gully is accessible and positioned where any discharge will be noticeable; and (d) with clear access for more than 2 m above the top of the gully grate, and not be enclosed. TAFE QUEENSLAND GOLD COAST

4.6.6.5 Alternative locations
Where it is not possible to comply with Clause , an overflow gully may be located as follows: (a) Recessed within an external wall, (see Figure 4.1(b)) provided— (i) the recess is not less than 300 mm wide and 600 mm high measured above the top of the gully riser, and shall be watertight; TAFE QUEENSLAND GOLD COAST

(ii) the gully riser is fully accessible; and (iii) the base of the recess is graded away from the building. TAFE QUEENSLAND GOLD COAST

(b) Located within a building, (see Figure 4.1(a)) provided — (i) the gully riser extends to floor level and be sealed with a removable airtight cover; (ii) an overflow pipe of the same size as the gully riser is installed at a grade of not less than 1.25% and terminates in the open air at an external wall of the building in accordance with Clauses and , and areas affected by flooding comply with Clause ; TAFE QUEENSLAND GOLD COAST

(iii) the overflow pipe is provided with a perforated removable or hinged cover that will not restrict discharge under surcharge conditions; and (iv) fixtures or appliances are not connected to the overflow pipe. TAFE QUEENSLAND GOLD COAST

NOTE: Additional gullies may be installed— (a) to receive the discharge from a domestic swimming pool; (b) on installations that serve multiple residential buildings and which have separate yards provided for each occupancy; TAFE QUEENSLAND GOLD COAST

(c) where a lower building may be affected by surcharge from a higher building; (d) where a lower fixture in a building may be affected by surcharge from higher fixtures; or (e) where such gullies need not comply with the requirements of Clause TAFE QUEENSLAND GOLD COAST

Height above lowest fixture
The grating of the gully must be installed 75mm above ground level (Clause ) to prevent the entry of stormwater to the sewer. The grate of the gully must also be at least 150mm below the lowest fixture in the building. See Figure 3. TAFE QUEENSLAND GOLD COAST

4.6.6.6 Height below lowest fixture
A minimum height of 150 mm shall be maintained between the top of the overflow gully riser and the lowest fixture connected to the drain. This height shall be measured vertically from the overflow level of the gully riser, or from the invert level of the overflow pipe, to the appropriate point given in Table 4.3. TAFE QUEENSLAND GOLD COAST

4.6.6.7 Height above surrounding ground
The minimum height between the top of the overflow gully riser, or the invert of the overflow pipe, and the surrounding ground surface level shall be 75 mm, except where the gully riser is located in a path or a paved area, where it shall be finished at a level so as to prevent the ponding and ingress of water. TAFE QUEENSLAND GOLD COAST

TABLE 4.3 POINT OF MEASUREMENT ON FIXTURES FOR HEIGHT ABOVE OVERFLOW GULLY
Soil fixture with an integral trap Floor waste gully or shower Soil fixture located in an outbuilding or room, flow of which is graded to an external doorway Other fixtures Top surface level of the water seal Top surface level of the grate the Overflow rim of the fixture Top surface level of the fixture outlet TAFE QUEENSLAND GOLD COAST

NOTE: Floor waste gullies (including those in shower areas) that have a non-return valve fitted to prevent backflow may be excluded provided that the top of the gully connected to the drain terminates at least 50 mm below such floor waste gullies. TAFE QUEENSLAND GOLD COAST

4.6.6.8 Height in flood-affected areas
The top of the gully riser in flood-affected areas shall be— (a) finished at a level not less than 150 mm above the declared flood level; or (b) sealed with a removable watertight cover with a vent of the same size as the gully, terminating at a level not less than the declared flood level and in accordance with Clause Where the above requirements cannot be achieved, no property shall gravitate to the authority’s sewer. TAFE QUEENSLAND GOLD COAST

Reflux valve AS3500.0:2003 Glossary of terms Reflux valve – A valve that prevents the reversal of flow by means of a flap or other mechanism.(page59) TAFE QUEENSLAND GOLD COAST

A reflux valve is a valve that is specifically designed for sewerage installations. It has a flap valve installed to give one-way flow. The flap valve opens to allow sewage to run from the property to the sewer main. If the flow is from the main into the property drain, as in a surcharge situation, the valve closes to prevent the flow. TAFE QUEENSLAND GOLD COAST

Reflux valves are not the preferred option for surcharge protection because they are prone to blockages, causing maintenance problems for the property owner. They are only installed if an ORG cannot be used. TAFE QUEENSLAND GOLD COAST

4.5.1 Location A reflux valve shall be located wholly within the property. TAFE QUEENSLAND GOLD COAST

4.5.2 Installation A reflux valve shall be installed where either— (a) the minimum height of the overflow relief gully and the lowest fixture specified in Clause cannot be achieved; or (b) a fixture is located in a basement and discharges to a sewage ejector or wet well and can be affected by a surcharge from a fixture at a higher level. TAFE QUEENSLAND GOLD COAST

4.5.3 Surcharging sewer Where surcharge is likely to occur and a reflux valve is to be installed, it shall be located in accordance with the following: (a) Where the drain has an inspection shaft, the reflux valve shall be installed adjacent to the shaft. (b) Where the drain has a boundary trap, the reflux valve shall be located immediately downstream from and adjacent to the outlet of the boundary trap. TAFE QUEENSLAND GOLD COAST

4.5.4 Reflux valve chambers Except where a reflux valve is installed in an accessible position within a building (see Clause ), or can be fully serviced and maintained from ground level, all reflux valves shall be installed within a chamber complying with Clause 4.8. TAFE QUEENSLAND GOLD COAST

Reflux valves Reflux valves within a building shall be installed in accordance with the following: (a) Where located above ground or floor surface level, the installation shall comply with the relevant requirements of Clause 4.5. (b) Where installed immediately below any floor slab or other structure, a clear space shall be provided above the reflux valve to facilitate maintenance. TAFE QUEENSLAND GOLD COAST

Ventilation of property drains
Property drains require ventilation for the following reasons: To maintain a balance of pressure needed to protect the water seals in drainage traps and fixture traps from siphonage. To prevent large volumes of sewer gases building up in the drainage system. To allow solid materials, which may stick to the drain walls, to dry out and fall off. This material can then be washed away with the flow of sewage. TAFE QUEENSLAND GOLD COAST

Main drain The ventilation of a drain must allow for a continuous air flow through the main property drain from one end to the other. This flow does not travel in only one direction. At times, depending on wind direction and strength the flow may reverse numerous times each day. The ventilation flow must be able to leave or enter both the downstream and upstream ends of the drain to be effective. TAFE QUEENSLAND GOLD COAST

Downstream ventilation
Inspection shaft installation When the drain has an inspection shaft the ventilation air can enter or leave the property drain and pass into the reticulated sewer without restriction. In this case the plumber does not have to make any provision for additional downstream ventilation. The tops of Inspection Shafts need to be finished as described in Figures 5 and 6. TAFE QUEENSLAND GOLD COAST

Light cover. TAFE QUEENSLAND GOLD COAST

Heavy cover TAFE QUEENSLAND GOLD COAST

Boundary trap installation
When the drain is fitted with a boundary trap the plumber has to provide a method of downstream ventilation because no airflow can pass the water seal of the trap. The simplest method is to fit the boundary trap shaft with a suitable ground vent as shown in Figure 1. Sometimes it is not possible to fit a ground vent to the shaft. If the shaft is constructed in a driveway or footpath, a ground vent would be a nuisance and liable to be damaged. TAFE QUEENSLAND GOLD COAST

Another reason ground vents cannot be fitted to some drains is that AS states that the ground vent must be 3m from openings into a building or 5 metres from an air duct intake. This amount of separation reduces the risk of odours entering the building. If a ground vent cannot be fitted on the top of the BT shaft a sealed access cap is required and a protective cover must be installed. (refer figure 5 & 6 unit notes) TAFE QUEENSLAND GOLD COAST

Garage House Sewer main Garden bed Driveway Property boundary BT – Heavy cover Property drain Garage TAFE QUEENSLAND GOLD COAST

Upstream ventilation AS Clause 3.9 requires that all property drains be fitted with an upstream drainage vent. This vent must be fitted downstream of any fixture or drainage trap connection. The unvented section of the drain, upstream of the vent must comply with the requirements of Clause Clause describes all the details relating to unvented branch drains and should be read in detail to fully understand its requirements. TAFE QUEENSLAND GOLD COAST

Maximum length The total length of an unvented branch drain, including the length of the fixture discharge pipe (see Figure 3.6), shall be no greater than the following: (a) 10 m from the vented drain to the weir of the trap, provided the length of the discharge pipe does not include a vertical drop, between the crown of the trap and the invert of the branch drain exceeding— (i) 2 m for water closet pans with DN 80 discharge pipes; TAFE QUEENSLAND GOLD COAST

(ii) 1.5 m, for basins and bidets fitted with ‘S’ traps; and (iii) 2.5 m for all other fixtures. (b) 10 m to the weir of a disconnector gully. (c) 10 m to a sullage dump point located in a caravan park. TAFE QUEENSLAND GOLD COAST

3.9 VENTING OF DRAINS 3.9.1 General Vents in drains shall be provided— (a) at both ends of any drain that incorporates a boundary trap; (b) at the upstream end on any drain not incorporating a boundary trap; (c) at the upstream end of any branch drain to which a fixture trap or floor waste gully is connected, if the distance from the weir of the trap to the vented drain exceeds 10 m; TAFE QUEENSLAND GOLD COAST

(d) at the upstream end of a branch drain to which a gully is connected, or a sullage dump point located in a caravan park is connected, if the distance from the weir of the trap to the vented drain exceeds 10 m; (e) at the upstream end of any DN 100 branch drain to which three or more water closet pans are connected; and TAFE QUEENSLAND GOLD COAST

(f) along the line of a DN 100 vented drain where 10 or more water closet pans are installed in a toilet block and are each individually connected in accordance with Clause TAFE QUEENSLAND GOLD COAST

3.9.2 Location Upstream vent The upstream vent on any drain shall be connected— (a) to the drain downstream of any fixture or drainage trap connection, provided any unvented section of drain upstream of the vent branch connection complies with Clause ; or (b) at the vent extension of a stack located at or near the upstream end of the drain, provided any unvented section of drain upstream of the stack branch connection complies with Clause 3.10. TAFE QUEENSLAND GOLD COAST

Downstream vent The downstream vent on any drain, where required by Clause 3.9.1(a), shall be connected within 10 m of the boundary trap riser provided no other fixture is connected between the boundary trap riser and the vent connection. TAFE QUEENSLAND GOLD COAST

3.9.2.3 Low level vent (ground vent)
Where a low level vent is provided in accordance with Clause , it shall be located so that— (a) the inlet of the vent is not less than 150 mm above ground level; (b) it terminates not less than 3 m from any opening into a building or 5 m from any air duct intake; and (c) it is not liable to be damaged or cause injury or obstruction. TAFE QUEENSLAND GOLD COAST

3.9.3 Size of drainage vents Minimum size Drainage vents shall be sized in accordance with Table 3.5, and— (a) the upstream vent on any main drain shall be not less than DN 50; (b) the upstream vent on any branch drain shall be not less than DN 40; (c)the section of drain acting as a vent shall be not less than DN 65 (see Figure 3.5); TAFE QUEENSLAND GOLD COAST

(d) notwithstanding the number of fixture units discharging to the drain, the minimum size of any ground vent pipe shall be DN 50; and (e) if an air admittance valve is used to terminate an upstream vent, Table 6.6 shall apply. NOTE: Branches connected into a positive pressure area, such as near boundary traps in multistorey buildings, may need additional venting. TAFE QUEENSLAND GOLD COAST

Rating of vents Where two or more vents are directly connected to a drain, these vents may take the place of the single vent required by Table 3.5, provided the sum of the ratings is equal or greater than the vent rating for the single vent. TAFE QUEENSLAND GOLD COAST

TABLE 3.5 SIZE AND RATING OF VENTS
Size of vent pipe Fixture units discharging to Vent rating DN Drain 40 > ≤ 10 0.5 50 > ≤ 30 1 65 > ≤ 175 2 80 > ≤ 400 3 100 > _ 6 TAFE QUEENSLAND GOLD COAST

3.9.3.3 Connection of vent to drain
Where the minimum size of DN 65 for a drain line exists, a minimum DN 50 vent pipe may be connected as shown in Figure 3.5. Example: Loading in fixture units discharging to drain = 36. Required size of drainage vent = DN 65 (rating of 2). Other vents on drain are two DN 50 vents, which give a combined rating of 2. The two other stack or drainage vents in combination may take the place of a single DN 65 vent. TAFE QUEENSLAND GOLD COAST

FIGURE 3.5 TYPICAL CONNECTION OF VENT TO DRAIN
TAFE QUEENSLAND GOLD COAST

Vent extending from fixture connection

Vent from down stream junction

Fixture classification
Sanitary plumbing fixtures are classified into two groups: Soil fixtures Soil fixtures are those whose primary purpose is to dispose of human waste or fluids. This includes Water Closet pans (toilets), urinals, slophoppers, autopsy tables, bedpan washers or sanitary napkin disposal units. Discuss each topic with students. TAFE QUEENSLAND GOLD COAST

Waste fixtures All other fixtures, whose primary use produces a wastewater discharge. TAFE QUEENSLAND GOLD COAST

Soil fixtures Waste fixtures TAFE QUEENSLAND GOLD COAST

Definition AS3500.0:2003 Glossary of terms Fixture: A receptacle with necessary appurtenances designed for a specific purpose, the use or operation of which results in a discharge into the sanitary plumbing and sanitary drainage system. (page 19) TAFE QUEENSLAND GOLD COAST

Soil fixture A water closet pan, urinal, slop hopper, autopsy table, bed pan washer or sanitary napkin disposal unit. (page 19) Waste fixture Ay fixture other than a soil fixture. (page 19) TAFE QUEENSLAND GOLD COAST

Soil fixture: Discharges offensive body wastes. Waste fixture: Any fixture other than a soil fixture. TAFE QUEENSLAND GOLD COAST

Examples of waste & soil fixtures
Water closet Urinal Slop hopper Bed pan washer Sanitary napkin disposal unit TAFE QUEENSLAND GOLD COAST

Waste fixtures: Basin Bath Sink Trough Shower TAFE QUEENSLAND GOLD COAST

From a drainage design viewpoint, the difference between the soil and waste fixtures is that fewer methods of connection from soil fixtures to the drain are permitted by AS3500. Soil fixtures are not allowed to connect to DG’s, ORG’s or floorwaste gullies. The reason is that the discharge from soil fixtures would allow offensive odours to pass through the open grates of these gullies. TAFE QUEENSLAND GOLD COAST

Fixture traps All sanitary fixtures must be fitted with traps to prevent the gases in the sewerage system entering buildings. The gases in the sewerage system have an offensive odour but may also contain poisonous and potentially explosive gas mixtures. TAFE QUEENSLAND GOLD COAST

Some fixtures have the trap built-in to their design. This is known as an ‘integral’ trap. Water closet pans are all made this way. Some types of basins and wall-hung urinals are also available with integral traps. All other fixtures are fitted with threaded outlet connections to allow the fitting and removal of the trap. TAFE QUEENSLAND GOLD COAST

Example of an integral trap TAFE QUEENSLAND GOLD COAST

‘P’ traps P traps have outlets which discharge on grade. TAFE QUEENSLAND GOLD COAST

‘S’ traps S traps have outlets which discharge vertically. TAFE QUEENSLAND GOLD COAST

Both P and S traps may be used for any fixture connection to the sanitary plumbing system or drain. The choice of trap is governed by the location of the connection point that has been left for the fixture. The size of the fixture trap and discharge pipe, for all fixtures, is listed in AS Table 6.1. TAFE QUEENSLAND GOLD COAST

6.4 TRAPPING OF FIXTURES AND APPLIANCES
6.4.1 General Each sanitary fixture and appliance shall have a trap or self-sealing device. The trap or selfsealing device shall be in the same room as the fixture and/or appliance that it serves and be accessible. TAFE QUEENSLAND GOLD COAST

6.4.2 Water seal Under normal operating conditions, fixture traps shall retain a water seal of not less than 25 mm. Traps that are installed in a pressurized chamber shall retain a water seal of not less than 70 mm when the maximum pressure within the chamber is applied. TAFE QUEENSLAND GOLD COAST

6.4.3 Location of traps and self-sealing devices
Traps and self-sealing devices shall be connected as close as possible to the outlet of the fixture or appliance being served. The maximum distance from the outlet of a fixture to the surface of the water seal of a trap shall be 600 mm for other fixtures except for floor waste gullies (see Clause ) and fixture pairs (see Clause TAFE QUEENSLAND GOLD COAST

6.4.4 Multiple outlets General The following fixtures, or a combination of them, may be connected in pairs to a single fixture trap provided the fixtures have similar spill levels: (a) Basins. (b) Sinks. (c) Showers. (d) Laundry troughs. (e) Ablution troughs. TAFE QUEENSLAND GOLD COAST

6.4.4.2 Distance between outlets
Pairs of fixtures shall be connected so that the distance between their outlets does not exceed 1.2 m (see Figure 6.1). TAFE QUEENSLAND GOLD COAST

Fixture connection methods
The discharge pipe from fixtures in a building must be connected to the main drain using a suitable method. In modern buildings unvented branch drains are the most commonly used method to make connections between fixture discharge pipes and the main drain. TAFE QUEENSLAND GOLD COAST

Unvented branch drains
AS Clause 3.10 and Figure 3.6 give the details of unvented branch drain installations and the details of fixture connections to unvented branch drains. Unvented branch drains may be constructed from DN65, 80 or 100 pipe. The size is determined from the type of fixtures connected and the ‘fixture unit rating’. Table 3.6 gives the details. TAFE QUEENSLAND GOLD COAST

Even though smaller sizes may be used plumbers usually install the entire drain for a domestic building in DN100 pipe. This is cheaper and easier in most cases. Fixture discharge pipes are usually connected to 100 x 88o bend on the end of the unvented branch drain. A suitable size reducer is used to make the connection between the discharge pipe and the bend TAFE QUEENSLAND GOLD COAST

If the trap of the fixture is at a low level, such as a bath, shower or floor waste gully (FWG), it may be connected on grade to the end of the unvented branch drain with an eccentric taper fitting. These fittings are usually known as LIT’s (short for Level Invert Taper) by plumbers. Figure 3.1 in AS3500 shows this type of connection. TAFE QUEENSLAND GOLD COAST

When DN80 or DN65 unvented branch drains are connected to the DN100 main drain, the size change is made with an LIT. Whenever LIT’s are installed on grade, they must be laid so that the tops of the pipes are in alignment. This allows for uninterrupted air flow along the drains. See Figure 14. TAFE QUEENSLAND GOLD COAST

3.10 UNVENTED BRANCH DRAINS
General The requirements of this Clause shall apply to— (a) ground-floor connections to a vented drain installed on grade, located below or above the ground (see Clause 9.12); or (b) connections to a disconnector gully. TAFE QUEENSLAND GOLD COAST

Sizing The size of an unvented branch drain shall be such that the sum of the fixture unit ratings, as given in Table 6.1, shall not exceed the maximum loading specified in Table 3.6. TAFE QUEENSLAND GOLD COAST

TABLE 3.6 SIZE OF UNVENTED BRANCH DRAINS
Size of pipe DN Maximum fixture unit loading 65 80 100 5 fixture units (excluding a water closet pan or slop hopper); or 10 fixture units from one floor waste gully 12 fixture units (including not more than one water closet pan or slop hopper) 30 fixture units (including not more than two water closet pans or 2 slop hoppers) TAFE QUEENSLAND GOLD COAST

Fixture unit rating See table 6.1 AS3500.2:2003 (page63) TAFE QUEENSLAND GOLD COAST

Maximum length The total length of an unvented branch drain, including the length of the fixture discharge pipe (see Figure 3.6), shall be no greater than the following: (a) 10 m from the vented drain to the weir of the trap, provided the length of the discharge pipe does not include a vertical drop, between the crown of the trap and the invert of the branch drain exceeding— (i) 2 m for water closet pans with DN 80 discharge pipes; (ii) 1.5 m, for basins and bidets fitted with ‘S’ traps; and (iii) 2.5 m for all other fixtures. TAFE QUEENSLAND GOLD COAST

(b) 10 m to the weir of a disconnector gully. (c) 10 m to a sullage dump point located in a caravan park. TAFE QUEENSLAND GOLD COAST

Vertical sections Where the fixture discharge pipe is the same size as the unvented branch drain to which it connects, the drain to the trap shall have a maximum of two vertical jump-ups, each not exceeding 2 m in height, and separated by not less than 300 mm of graded pipe. TAFE QUEENSLAND GOLD COAST

3.10.5 Connection of fixture discharge pipes
Where fixtures are connected to unvented branch drains, the requirements for the fixture discharge pipes shall be the same configuration as for the connection of fixtures to group vented branches and shall comply with Clauses and and Figure 3.6. TAFE QUEENSLAND GOLD COAST

Disconnector gullies Discharge pipes from waste fixtures (but not from soil fixtures) and Floorwaste Gullies (FWG’s) may connect to the main drain through a disconnector gully (DG) on the end of an unvented branch drain. TAFE QUEENSLAND GOLD COAST

NOTE Remember that a DG may be used as an ORG for the installation. Fixtures may be connected to the ORG in exactly the same way as they are connected to DG’s. These connections can be done in one of two different ways: TAFE QUEENSLAND GOLD COAST

Direct to DG A discharge pipe of the same size as the fixture trap is run to the DG in accordance with AS3500 Table 4.1. This Table gives the maximum length (unvented) of the discharge pipes of various fixtures, and states that the number of bends be used for the installation be kept to a minimum. See Figure 15. TAFE QUEENSLAND GOLD COAST

4.6.1 General Gullies may be used for one or more of the following purposes: As relief in the event of sewage surcharge (overflow relief gully). To provide disconnection between waste discharges and the remainder of the sewerage installation (disconnector gully). TAFE QUEENSLAND GOLD COAST

4.6.2 Installation Gullies shall— (a) be of the self-cleansing type; (b) be supported on a concrete footing of a thickness not less than 100 mm, with a width not less than 100 mm beyond the sides of the trap and extending upwards to not less than 100 mm above the base of the gully; TAFE QUEENSLAND GOLD COAST

(c) have the top of the gully riser, if of vitrified clay or PVC-U, protected from damage at ground level by means of a concrete surround of a minimum width of 100 mm and a minimum depth of 100 mm below ground level; and (d) have each gully riser provided with a grating to relieve surcharge. TAFE QUEENSLAND GOLD COAST

4.6.3 Maintenance of water seal
The water seal shall be permanently maintained in the gullies by — (a) the discharge from a waste fixture or floor waste gully in accordance with Table 4.1; TAFE QUEENSLAND GOLD COAST

Table 4.1 Connection of fixtures to disconnector gullies
Fixture Maximum unvented length of waste pipe (m) Basin or bidet with DN 40 traps and waste pipes All other waste fixtures and floor waste gullies with DN 50 or smaller waste pipes Floor waste gullies and fixtures with DN 65 or larger waste pipes3.5610 3.5 6 10 NOTE: Bends to be kept to a minimum TAFE QUEENSLAND GOLD COAST

(b) the discharge from a waste stack of not more than five floors in height; (c) water from a tap located over the gully; TAFE QUEENSLAND GOLD COAST

(d) waste fixtures or waste stacks connected into a gully riser, discharging below the level of the grating and above the surface level of the water seal (see Figure 4.1); or (e) the discharge from a charge pipe in accordance with Figure 4.3 and Clause TAFE QUEENSLAND GOLD COAST

4.6.4 Prohibited discharge Soil fixtures shall connect directly to the sewer drain and not discharge over the water seal of a gully. Surface or roofwater shall not discharge into the sewer drain. TAFE QUEENSLAND GOLD COAST

To DG via an unvented branch drain
A section of unvented drain may discharge into a DG. Fixture discharges from waste fixtures (but not from soil fixtures) may connect to this unvented branch drain. AS , Clause 3.11 describes these connections. See Figure 16. TAFE QUEENSLAND GOLD COAST

3.11 UNVENTED DRAINS DISCHARGING TO GULLIES
General Where only waste fixtures are received by a drain, the drain may connect to a gully. The maximum fixture unit loading and size of unvented branch drain shall comply with Table 3.6. TAFE QUEENSLAND GOLD COAST

3.11.2 Length of unvented section
The combined length of unvented drain and fixture discharge pipe shall not exceed 10 m. The fixture discharge pipe shall comply with Clauses and If the combined length of the unvented drain and fixture discharge pipe exceeds 10 m, the branch line shall be vented in accordance with Clause or Clause 6.9. TAFE QUEENSLAND GOLD COAST

Floor waste gullies Fixtures which are permitted to discharge to the main drain via a Floorwaste Gully (FWG) are listed in AS Table 4.4. AS :2003 (page 45) The outlet pipe work from the FWG may connect to either directly to an unvented branch drain or to a DG. TAFE QUEENSLAND GOLD COAST

Typical floorwaste gully (FWG) assembly
Grate 4 Way riser Floor waste gully 80 inlet – 50 outlet 80 inlet – 65 outlet 80 inlet – 80 outlet TAFE QUEENSLAND GOLD COAST

Using a FWG enables waste water from fixtures, such as baths, basins and showers as well as waste water spillage on floors, to be connected at one point. All fixtures connected must be in the same room as the FWG. This makes the FWG a useful alternative for fixture connections in bathrooms and similar situations. Figures 18 & 19 show how this connection may be made. TAFE QUEENSLAND GOLD COAST

F.W.G. Bath Shower Basin TAFE QUEENSLAND GOLD COAST

The maximum length of the unvented branch drain is 10 metres to the trap weir for DN 65 and greater pipe sizes – See examples 1 & 4. TAFE QUEENSLAND GOLD COAST

FWG AP Main (Vented) Drain DN 65 min. DN 50 10m max. 6m max. 2.5 m max. Example 1 Example 2 Example 3 Example 4 DN 65 or larger TAFE QUEENSLAND GOLD COAST

However, the maximum length of a DN 50 discharge pipe from a FWG connected directly to the drain shall be 2.5 metres and the total length of discharge pipe and unvented branch drain shall not exceed 10 metres – See example 1. TAFE QUEENSLAND GOLD COAST

A fixture discharge pipe to FWG shall be 2.5m maximum length. The discharge from the FWG may connect to a DG via an unvented branch drain, maximum length 10m. The maximum length of unvented branch drain from the DG to the main (vented) drain shall be 10metres. See example 2. TAFE QUEENSLAND GOLD COAST

The maximum length of a DN 50 discharge pipe from a FWG to a D.G. shall be 6 metres. See example 3. The maximum length of DN 65 or larger unvented branch drain from a FWG to a vented drain is 10 metres. See example 4. TAFE QUEENSLAND GOLD COAST

4.6.7 Floor waste gullies General For the purpose of this Clause, floor waste gullies shall be deemed as a fixture trap (see Figure 4.2). TAFE QUEENSLAND GOLD COAST

Permitted discharges Fixtures in Table 4.4, and fixture pairs in accordance with Clause 6.4.4, may be connected to floor waste gullies. Except for tundish discharges, these fixtures shall be located within the same room as the gully. Basins and drinking fountains that discharge to a floor waste gully shall have a trap installed immediately adjacent to the outlet of the fixture. Where foaming is likely to cause a problem, fixtures should not discharge through a floor waste gully. TAFE QUEENSLAND GOLD COAST

4.6.7.3 Connection of fixtures
Each fixture, or fixture pair, that is connected to a floor waste gully shall be connected by a separate waste pipe at a grade of not less than 2.5% and with a length not exceeding that specified in Table 4.4. TAFE QUEENSLAND GOLD COAST

Maximum length of waste pipe, m Waste fixture Connected to riser of floor waste gully Connected to submerged inlet floor waste gully (see Figure 4.2A) Fixture untrapped Fixture trapped Fixture trapped or untrapped Basin, drinking fountain Not permitted 2.5 2.5 (trapped only) Bath, shower/bath 1.2 Bidet Cleaners’ sink. Clothes-washing machine Bar sink (commercial), glass- washing machine Bar sink (domestic) Shower Bain-marie, sterilizer Laundry and ablution trough Refrigerated cabinet Tundish (see Clause ) 10.0 TAFE QUEENSLAND GOLD COAST

4.6.7.4 Wastepipes discharging to floor waste gullies (FWGs)
Wastepipes discharging to FWGs shall not be extended and trap vents shall not be installed on fixture discharge pipes. TAFE QUEENSLAND GOLD COAST

Prohibited location Floor waste gullies, with the exception of untrapped floor drains, shall not be installed in any refrigerated coolroom, airconditioning return air plenums or the like. TAFE QUEENSLAND GOLD COAST

Removable grate Floor waste gullies shall be installed with an accessible removable grate and a riser not less than DN 80 at floor surface level. Where the sole function of the floor waste gully is to dispose of water spillage and washdown water, a DN 50 outlet and riser may be used. TAFE QUEENSLAND GOLD COAST

Height of gully riser The height of the gully riser shall be measured from the top of the water seal to the floor surface level and shall comply with the following: (a) For floor waste gullies with connections to the gully riser— the minimum height shall comply with Table 4.5; and the maximum height shall be 600 mm. (b) For floor waste gullies with submerged inlets, the minimum height shall be 100 mm. TAFE QUEENSLAND GOLD COAST

TABLE 4.5 MINIMUM HEIGHT OF FLOOR WASTE GULLY RISERS
Waste fixtures connected to gully riser Size of gully riser Minimum height 88.5 entry Water seal to floor level 45 entry All permitted waste fixtures includind 1 bath 80 100 200 150 TAFE QUEENSLAND GOLD COAST

4.6.7.8 Discharges from tundishes
In addition to the discharges permitted in Table 4.4, tundishes receiving discharges from water heater drains, airconditioning units, other condensate lines and the like, may discharge to a floor waste gully. The maximum length of the discharge pipe shall not exceed 10 m (see Figure 4.3(a)). TAFE QUEENSLAND GOLD COAST

4.6.7.9 Size of gully trap outlet
The minimum size of floor waste gully trap outlets shall be as specified in Table 4.6. TAFE QUEENSLAND GOLD COAST

TABLE 4.6 FLOOR WASTE GULLY OUTLET SIZE
Maximum number of fixture units discharging into gully riser Minimum nominal size of outlet DN 3 10 including the discharge from one bath >10 50 65 80 TAFE QUEENSLAND GOLD COAST

4.6.7.10 Connection of waste pipes
Individual waste pipes connecting into a floor waste gully shall either— enter the riser at an angle between 45° and 88°, as close as practicable to but above the level of the water seal; or for a submerged-inlet floor waste gully, enter the gully at an angle of 88°. TAFE QUEENSLAND GOLD COAST

4.6.7.11 Size of waste pipes from fixtures
The size of waste pipes from fixtures connecting into floor waste gullies shall be as given in Table 6.1. AS3500.2:2003 (page 63) TAFE QUEENSLAND GOLD COAST

4.6.8 Charging floor waste gullies
General (a) Where a floor waste gully is located in a position that cannot receive a waste discharge, the water seal shall be maintained by the following: (b) A charge pipe from a flushing device, connecting at the heel or the base of the flush pipe with a union. The charge pipe shall enter the floor waste gully at 45°, not less than 50 mm above the water seal and shall be silver brazed or joined by a union to the riser (see Figure 4.3(b)). TAFE QUEENSLAND GOLD COAST

(c) A charge pipe from a mechanical trap-priming device extended to floor drain within the same room or compartment (see Figure 4.3(c)). (d) A lockshield (shrouded) hose tap installed in the same room, and with a graded floor. TAFE QUEENSLAND GOLD COAST

Installation The charge pipe shall be in the size range of DN 6 to DN 15. (a) Charge pipes from flushing devices, taps sets or hot water relief valve drains shall not exceed 10 m in length. (b) Charge pipes from mechanical priming devices shall be installed in accordance with the manufacturer’s installation instructions. NOTE: The charge pipe to the floor gully should be installed so as not to impede access for maintenance. TAFE QUEENSLAND GOLD COAST

Stacks Stacks are used to connect fixtures in multi-storey buildings. AS3500.0, the Glossary of Terms, describes a stack as: ‘any vertical pipe including offsets, extending through more than one floor level’. TAFE QUEENSLAND GOLD COAST

In a stack installation, the vertical pipework, through which discharges flow, must extend through ‘more than one floor level’. ie there must be fixture connections on two levels (at least) for the installation to be described as a stack. TAFE QUEENSLAND GOLD COAST

There are restrictions on fixture connections near the base of stacks. See AS3500.2, Figure 6.4. Ground floor fixtures connect directly to the drain, outside the restricted zone. TAFE QUEENSLAND GOLD COAST

Drainage connections for stacks
When a building has one or more stack installations in its design, the person designing and installing the drain must make provision to connect them to the drain. The AS describes numerous systems of stack design. Each system has particular requirements for the connection of the fixture discharge pipes and vents to the stack. TAFE QUEENSLAND GOLD COAST

From a drainage point of view, designers need to know that a suitably sized bend or junction must be located on the drain in a position to connect the stack. If the position of the stack on the drain is within the requirements Clause 3.10, the vent from the top of the stack (regardless of the stack system used) may also act as the drainage vent. TAFE QUEENSLAND GOLD COAST

Trade waste connections
In industrial and commercial plumbing installations, some types of fixture discharges contain products that may be harmful to the sewerage installation. TAFE QUEENSLAND GOLD COAST

Harmful discharges are those such as: Grease Fats Acid Solvents Oil Plaster Clay Hot water (over 380 C) Sand, Silt, Grit or Dirt Other solids TAFE QUEENSLAND GOLD COAST

These types of discharges require pre-treatment between the fixture and the connection to the property drain. Each type of harmful discharge requires a specific type of pre-treatment facility. Before any drainage design is considered the Local Authority should be consulted to discuss the requirements for pre-treatment. NOTE The design of the pre-treatment systems is a separate area of study, not covered by this text. TAFE QUEENSLAND GOLD COAST

Connection of fixtures in two storey houses
Many modern homes are designed with two storeys. Sanitary fixtures are often located on the upper level as well as on the ground floor. Suitable drains must be designed to allow the connection of all the fixtures in these types of installations. It may possible to run discharge pipes from upper level fixtures to drainage connection points at ground level. These pipes may be concealed, or exposed on the exterior walls. In modern buildings designers try to conceal pipes and other services within the building structure whenever possible. TAFE QUEENSLAND GOLD COAST

Some discharges will be able to connect in this way without the need for venting. eg a discharge pipe from a some fixtures can run 6m (unvented) to a DG. This can be extended to 10m if an unvented branch drain connects the fixture to the DG. Discharge pipes to direct connections on the end of unvented branch drains are limited to 2.5m (unvented). If the maximum lengths of discharge pies are exceeded for the type of connection chosen, a trap vent (as per Clause 7.5.1) or an air admittance valve (as per Clause 6.9) will be required. TAFE QUEENSLAND GOLD COAST

A common way to eliminate the need for extra vents is to use a jump-up on the drain to bring it to the first floor level. Often a suspended drain is installed in the space between the ceiling and the first floor level. Fixtures can then connect to this drain using unvented branch drain methods as described in Clause 3.10 and shown in Figure 3.6 of AS TAFE QUEENSLAND GOLD COAST

DN100 vented drain 1st floor Roof 1 floor level Jump-up Drain vent An example of a jump-up used in a two storey house, showing connection of fixtures on the 1st floor level to a section of unvented branch drain. Ground floor connections to a section of unvented branch drain TAFE QUEENSLAND GOLD COAST

Gradient Plumbers install discharge pipes from fixtures, and drainage pipes that run to sewer connections on a downward slope. This slope is described as the grade or gradient. The gradient allows gravity to provide the flow from the fixture outlets to the sewer mains. The gradient can be described as a ratio, eg 1:60 or as a percentage, eg 1.65%. TAFE QUEENSLAND GOLD COAST

Self-cleansing action
The minimum specified gradients have been selected in order to provide a self-cleansing action for drainage installations. A self-cleansing action ensures that all the material, including solids and paper, are washed away by normal fixture discharges. The speed of the water flow provided by the use of correct gradients provides this capability. TAFE QUEENSLAND GOLD COAST

If drainage pipes are installed at less than the minimum gradient there is a possibility of water slowly trickling away whilst leaving behind solid material. If enough of this solid material accumulated blockages could occur. TAFE QUEENSLAND GOLD COAST

Wherever possible, plumbers install drains on the minimum gradient. This is to reduce the amount of soil that has to be moved during excavations. The minimum gradients that may be used for drainage installations are specified in AS (Table 3.2). In rare situations where gravity flow cannot be used, sewage pumping equipment will be required to carry away discharges to the sewer main. AS (Section 10) describes the requirements for pumped discharges. TAFE QUEENSLAND GOLD COAST

3.4 GRADES OF DRAINS 3.4.1 Minimum grade The normal minimum grade of vented and unvented drains shall be as given in Table 3.2. TAFE QUEENSLAND GOLD COAST

TABLE 3.2 MINIMUM GRADES OF DRAINS
Nominal size DN Minimum gradient % 65 80 100 125 150 225 300 2.50 1.65 1.25 1.00 0.65 0.40 TAFE QUEENSLAND GOLD COAST

Reduced grades Sometimes part of the building structure, or another service, etc is in the way of the drain and the minimum grade cannot be achieved. Reduced grades as listed in AS (Table 3.3) may be used in situations where the normal minimum grades cannot be used. The Table specifies a minimum number of fixture units that must be connected to the drain if the reduced grade is used. The additional flow from the fixtures provides a flushing action to move solids along the drain. TAFE QUEENSLAND GOLD COAST

3.4.2 Reduced grades Where the minimum gradient, as specified in Table 3.2, cannot be obtained, drains may be laid at the reduced grades given in Table 3.3. Where soil fixtures are connected, the fixture unit loading on the drain shall be not less than the appropriate value given in Table 3.3. If this loading cannot be achieved, provision shall be made for flushing the drain. TAFE QUEENSLAND GOLD COAST

TABLE 3.3 Minimum fixture rating for reduced grade drains of drains

Steep gradients Clause states that any section drain that is laid on a grade of more than 20% (1:5) must have anchor blocks installed. An anchor block is a reinforced concrete block poured around the drain and extending into the undisturbed soil on either side of the trench. They must be installed at the top and bottom of the inclined section and at spacings of no more than 3 metres apart along the slope. The purpose of the anchors is to stop movement of the drain during backfilling operations or due to settling of the soil over time TAFE QUEENSLAND GOLD COAST

3.4.3 Steep grades Where it is necessary to install a drain on a grade between 20% and vertical, anchor blocks shall be installed— (a) at the bend or junction at the top and bottom of the inclined drain; and (b) at intervals not exceeding 3 m. TAFE QUEENSLAND GOLD COAST

3.4.4 Anchor blocks Anchor blocks for drains up to DN 150 shall be of reinforced concrete having two reinforcing rods of not less than 9 mm diameter. The reinforcing rods shall be bent to a radius that is 100 mm greater than the outside diameter of the pipe (see Figure 3.2). Anchor blocks shall— (a) be not less than 150 mm in thickness; (b) extend across the full width and be firmly keyed into the sides of the trench; (c) extend above the top of the pipe to a minimum height of 150 mm; (d) extend below the base of the trench for a minimum depth of 150 mm; and (e) not cover any flexible joint. TAFE QUEENSLAND GOLD COAST

Jump-ups AS (The Glossary of Terms) describes a jump-up as a section of drain joining two drains at different levels. Two different forms of jump-ups are described: TAFE QUEENSLAND GOLD COAST

Vertical jump-up Plumbers often use vertical jump-ups when the sewer main connection point is deep below ground level. A vertical jump-up is used to bring the property drain to a higher level to minimise excavation, and to limit the amount of trench shoring that may need to be used. Vertical jump-ups are also used when a below ground drain enters under a building and rises to become a drain suspended under a floor structure above ground. TAFE QUEENSLAND GOLD COAST

Graded jump-up Plumbers often use graded jump-ups when the slope of the land would require deep excavation to use minimum gradient. TAFE QUEENSLAND GOLD COAST

4.10 JUMP-UPS Jump-ups in drains shall be constructed in accordance with the following: (a) The bend at the base of the vertical section of drain shall be supported on a concrete footing of a thickness not less than 100 mm and extending upwards not less than 100 mm. (b) Either a bend incorporating a full-size inspection opening or a junction fitting shall be used at the top of the vertical section of drain (see Figure 4.7). TAFE QUEENSLAND GOLD COAST

(c) Branch drains shall connect to the vertical section, using junction fittings described in Clause 4.9 and shall be fully supported. (d)The vertical section shall be protected and supported during the installation and placement of backfilling. TAFE QUEENSLAND GOLD COAST

Materials All of the materials that may be used for the installation of sanitary plumbing and drainage are listed in AS The standard lists the specification for the material, any limiting conditions on the use of the material and jointing methods. TAFE QUEENSLAND GOLD COAST

Plumbers choose materials for installations based on the cost of pipe and fittings and the ease of use. The suitability of the material for the type of installation must be considered in some cases. Eg, a drain for a chemical plant installation may have different requirements than a domestic drain. TAFE QUEENSLAND GOLD COAST

Sometimes architects or engineers are employed to design drainage installations for industrial and commercial jobs. They usually select and specify the materials for these jobs TAFE QUEENSLAND GOLD COAST

The most commonly used material for domestic drainage installations is unplasticized poly vinyl chloride (UPVC) usually referred to by plumbers as PVC. PVC is cheap, light, easy to cut and join, has a wide range of fittings available and is suitable for most jobs. TAFE QUEENSLAND GOLD COAST

Junctions Branches are connected to the main drain by the use of junctions. These junctions must be swept in the direction of flow. AS Clause 4.9 gives details of the various types of junction connections that are permitted and Figure 4.6 shows some of the options. TAFE QUEENSLAND GOLD COAST

Usually, in domestic plumbing, the main drain and the branch drains are of the same size and on the same level and gradient. The most commonly used method to connect these drains is to use either a 45o junction (see Figure 26), or a 45o junction fitted with a 45o bend (see Figure 27) if the branch drain connection is at right angles to the main drain. TAFE QUEENSLAND GOLD COAST

4.9 JUNCTIONS IN DRAINS Drains shall be joined at grade to each other by means of a sweep junction or an oblique junction fitting at an upstream angle of not greater than 60° and shall comply with the following: (a) All junctions shall be swept in the direction of flow. (b) Double ‘Y’ junctions shall not be used to make connections in a horizontal plane. TAFE QUEENSLAND GOLD COAST

(c) Where a jump-up in a drain is connected to a junction on its back, the arm of the junction shall be independently supported. (d) Where unequal junctions are used, the soffit of the branch drains shall be level with or higher than the soffit of the pipe to which it connects. TAFE QUEENSLAND GOLD COAST

(e) Where an equal junction is used to make the connection of a branch drain the same size as the main drain, the entry level of the branch drain may be on grade. (f) Junctions installed in the vertical plane shall not be used for the connection of stacks. TAFE QUEENSLAND GOLD COAST

(g) where the junction is a swept entry type with a throat radius of 50 mm the invert of the branch drain shall be at least 10 mm higher than the soffit of the main drain (see Figure 4.6). TAFE QUEENSLAND GOLD COAST

55 AS/NZS :2003 FIGURE 4.6 TYPICAL ARRANGEMENT FOR GRADED BRANCH DRAINS ENTERING MAIN DRAIN TAFE QUEENSLAND GOLD COAST COPYRIGHT

4.9.2 Square junctions Square junctions in drains shall only be used— (a) at the top of a jump-up at the point of connection; (b) at the connection of an inspection shaft to a graded drain; (c) at the connection of a drain to a boundary trap riser; TAFE QUEENSLAND GOLD COAST

(d) where a vent is connected to a boundary trap riser; (e) as the inlet riser of a gully or floor waste gully; (f) as an inspection opening; or (g) at the top of a jump-up in a drain, in lieu of a bend and inspection opening. TAFE QUEENSLAND GOLD COAST

4.9.3 Junctions installed in vertical plane
Sweep and oblique junctions may be laid in the vertical plane for the connection of a single discharge pipe or a drain, provided the vertical riser does not exceed 2 m in height, above the invert of the main drain, and in accordance with the following: TAFE QUEENSLAND GOLD COAST

(a) Branch drains connected off the vertical riser shall be independently supported. (b) Where a vertical riser is to be extended to ground level and/or the distance between the invert of the main drain and the invert of the branch drain exceeds 1 m, concrete shall be used as follows: (i) For sweep junctions beneath the lower half of each junction, to a minimum thickness of 100 mm. (ii) For oblique junctions beneath the junction, to a minimum thickness of 100 mm and continued up vertically to the underside of the bend fitted to the junction fitting. TAFE QUEENSLAND GOLD COAST

Inspection openings Inspection openings are provided on drains to assist during drain laying operations (visual aligning through mirrors, inserting of test plugs) and to provide access for maintenance. AS Clause and Figure 4.4 provide details of the locations of inspection openings required TAFE QUEENSLAND GOLD COAST

4.7 INSPECTION OPENINGS (IO)
4.7.1 Location Except where inspection chambers are provided, inspection openings for maintenance purposes (see Figure 4.4) shall be provided— (a) outside of a building, no further than 2.5 m, along each branch drain connecting one or more water closets or slop hoppers; (b) at intervals of not more than 30 m, with a minimum of one inspection opening on each main drain; TAFE QUEENSLAND GOLD COAST

(c) at the connection to the network utility operator’s sewer if not provided by the network utility operator; (d) on the downstream end of the drain where any drain passes under a building except where waste fixtures only are concerned; (e) where any new section of drain is connected to an existing drain; TAFE QUEENSLAND GOLD COAST

immediately at or upstream of the upper bend of a jump-up; at every change in horizontal direction of greater than 45° ; and at every change in gradient greater than 45° . TAFE QUEENSLAND GOLD COAST

4.7.2 Size (a) the same size as the drain for those up to DN 150; or (b) not less than DN 150 for those larger than DN 150. TAFE QUEENSLAND GOLD COAST

4.7.3 Types (a) Inspection branches or square junctions. (b) Inspection chambers in accordance with Clause 4.8. (c) Reflux valves. TAFE QUEENSLAND GOLD COAST

4.73 Access to inspection openings
Inspection openings located below paved, concrete or floor surfaces may be extended to surface level and be provided with an airtight removable cap TAFE QUEENSLAND GOLD COAST

4.7.5 Sealing Inspection openings and un used sockets shall be sealed with plugs or caps fitted with a gasket or sealing ring of an authorized type and securely held in position by a clip or strap, or threaded connection. When a plug or cap with a rubber ring or gasket is removed, a new rubber ring or gasket shall be fitted TAFE QUEENSLAND GOLD COAST

Drains in trenches Where drains are to be laid in trenches the requirements of AS Section 5 need to be followed. All trenching work must be done in accordance with OH&S requirements. Excavations over 1.5 metres deep require precautions to be taken to ensure the safety of workers and may require trench shoring. TAFE QUEENSLAND GOLD COAST

Excavation Trenches must be wide enough to provide 100mm of clearance between the wall of the pipe and the side of the trench. The trench must be excavated to a depth of at least 75mm deeper than the required location of the bottom of the pipe. This is the depth of bedding material required under the drain. TAFE QUEENSLAND GOLD COAST

5.2 EXCAVATION OF TRENCHES
5.2.1 Safety Excavation shall be conducted in accordance with workplace health and safety legislation. TAFE QUEENSLAND GOLD COAST

5.2.2 Trench dimensions Trenches shall be made with a minimum clearance of 100 mm on each side of the drain barrel, measured to the inside of the sheeting or side of trench. The trench width up to the level of the top of the drain shall be kept as narrow as practicable, but not less than the above minimum clearance. TAFE QUEENSLAND GOLD COAST

5.2.3 Over-excavation Where a trench has been excavated deeper than necessary, the excess depth shall be filled either with bedding material compacted to achieve a density as near to the original soil density as possible, or with concrete. TAFE QUEENSLAND GOLD COAST

5.2.4 Adjacent to the sewer Excavation by a machine shall not be carried out within 600 mm of the point of connection to the authority’s sewer main. TAFE QUEENSLAND GOLD COAST

5.2.5 Water-charged ground Excavation in water-charged ground shall be in accordance with the following: (a) Consideration shall be given to the effect on adjacent buildings and the trench. (b) The water level shall be lowered below the base of the proposed trench and maintained at that level during excavation, laying of the drain and backfilling of the trench. TAFE QUEENSLAND GOLD COAST

(c) Dewatering shall be carried out in accordance with the following: (i) Pumps and spearheads or similar devices may be used. (ii) The water removed shall be discharged into a location where it will not cause a nuisance or damage to property or the environment. (iii) The water removed shall not discharge, either directly or indirectly, into the sewer. TAFE QUEENSLAND GOLD COAST

5.2.6 Shoring and underpinning buildings
Where the bottom of the trench is adjacent to or below the footing and walls of any adjoining building or structure, the footing shall be adequately supported while the trench is open. TAFE QUEENSLAND GOLD COAST

3.8.2 Installation near and under buildings
(d) Where a drain is installed parallel to a footing, the trench shall be located as follows: (i) In Australia— (A) for single dwellings, as shown in Figure 3.4; and (B) for all other buildings or where the requirements of Item (A) cannot be achieved, the location of drains shall be as determined by a suitably qualified competent person. TAFE QUEENSLAND GOLD COAST

Bedding Sanitary drains are usually laid on a bed of material and surrounded by similar material to support the pipe on an even grade and protect it from damage. Figure 5.1 of AS shows a cross section of a drain laid in a trench. Suitable materials for bedding, side support and overlay include crushed rock, gravel, screenings, or recycled materials such as crushed concrete, bricks or roof tiles in nominal sizes 7-10mm. Other options for bedding of drains are listed in AS Clause 5.4. TAFE QUEENSLAND GOLD COAST

5.4 BEDDING OF DRAINS 5.4.1 General The bed onto which drains are laid shall be adequate to continuously support the installed drain accommodating the loads from the pipeline and surrounding ground. Bedding of drains shall comply with the following: (a) In stable soil, drains shall be directly supported on the undisturbed base of the trench, provided that the base of the trench is free from any rocks or tree roots. TAFE QUEENSLAND GOLD COAST

(b) In loam, clay, rock, shale, gravel or ground containing hard objects, drains shall be supported on a bedding material placed in the base of the trench. (c) Ground water or surface water entering the trench shall not disturb the bedding materials. TAFE QUEENSLAND GOLD COAST

5.4.2 Bedding materials Filling materials used for bedding of drains (see Figure 5.1) shall comply with one of the following: (a) Crushed rock, gravel screenings or recycled crushed concrete, roof tiles or bricks of nominal sizes 7–10 mm. (b) Cement mortar containing one part of portland cement and four parts of sand by volume thoroughly mixed with clean water to a workable consistency. TAFE QUEENSLAND GOLD COAST

(c) Cement mortar bedding shall be used where the base of the trench is rock or shale and where the grade is greater than 20%, and it shall— (i) be a minimum depth of 50 mm measured below the barrel of the pipe; (ii) be not less than 75 mm wide; (iii) be kept clear of flexible joints; and (iv) have pipes supported at not greater than 1.5 m from the centre, prior to placing the mortar bedding. TAFE QUEENSLAND GOLD COAST

(d) Sand shall be free running, capable of passing through a 2 mm mesh sieve, and shall not contain clay, organic or any other deleterious materials. NOTES: 1 Cast iron and ductile iron pipes may be unsupported for up to 600 mm either side of each pipe joint. 2 For installation of PVC-U pipe systems see AS 2032. TAFE QUEENSLAND GOLD COAST

5.4.3 Pipe side support and overlay materials
Pipe side support and pipe overlay material shall not be inferior to the pipe bedding material. TAFE QUEENSLAND GOLD COAST

Concrete supports 100mm thick concrete support pads are used under some parts of the drain. They provide a level of protection for the drainage fitting they support. This support is particularly necessary when a drain blockage is being cleared by the use of a plunger. Clause 5.3 explains that these pads are located under traps, inspection risers and bends forming risers. TAFE QUEENSLAND GOLD COAST

5.3 CONCRETE SUPPORT FOR DRAINS
Concrete pads used to support drains shall be a minimum of 100 mm thick and shall be laid— (a) under gully traps and boundary traps of material other than cast iron; (b) under all inspection junctions where a riser is brought to the surface; (c) under all junctions and bends greater than DN 65 forming risers from the drain; and (d) not closer than 20 mm to flexible joints. TAFE QUEENSLAND GOLD COAST

Backfill Trenches are backfilled after the drain is laid to the same level as the surrounding ground. The backfill material is usually the same soil previously excavated. The backfill material should contain no builders waste, bricks, rocks etc. If the soil, which was excavated, is unsuitable for backfilling, appropriate material must be obtained and used. TAFE QUEENSLAND GOLD COAST

5.4.4 Bedding and backfill The sanitary drainage services shall be surrounded with not less than 75 mm of compacted sand, or fine-grained soil, with no hard-edged object permitted to come in contact with or rest against any pipe or fitting (see Figure 5.1). Backfill shall be free from builder’s waste, bricks, concrete pieces, rocks or hard matter larger than 25 mm and no soil lumps larger than 75 mm. TAFE QUEENSLAND GOLD COAST

DIMENSIONS IN MILLIMETRES FIGURE 5.1 TYPICAL BEDDING OF DRAINS

Cover over drains Drains must be buried deep enough to prevent damage to the drain, or deformation due to vehicular loadings. AS Table 3.4 gives a listing of the required cover for different materials and different traffic types which may pass over the drain. If the drain does not have sufficient cover to meet the requirements in the Table, it can be protected from damage by laying paving over the top of the drain. The details are listed in Clause TAFE QUEENSLAND GOLD COAST

3.7 DEPTH OF COVER 3.7.1 General Drains shall be laid in a manner that provides protection against mechanical damage and deformation due to vehicular loadings. TAFE QUEENSLAND GOLD COAST

3.7.2 Depth of cover in public areas and private areas
Drains shall be laid with a depth of cover, measured from the top of the pipe socket or inspection opening to the ground surface, as specified in Table 3.4, unless the productspecific Standard specifies, or the manufacturer recommends, a greater depth of cover. Fittings that form part of a sanitary drainage installation shall not be installed at or above ground level. TAFE QUEENSLAND GOLD COAST

3.7.3 Drains without adequate cover
Drains constructed of materials having less than minimum cover as specified in Table 3.4, or less than the manufacturer’s installation recommendations, shall be covered by at least 50 mm of overlay and then shall be paved with— (a) 100 mm minimum thickness of reinforced concrete, where subject to heavy vehicular loading; TAFE QUEENSLAND GOLD COAST

(b) 75 mm minimum thickness of brick or concrete paving, where subject to light vehicular traffic; and (c) 50 mm minimum thickness of brick or concrete paving, where not subject to vehicular traffic. The paving shall extend the full width of the trench. NOTE: Also refer to the manufacturer’s recommendation. TAFE QUEENSLAND GOLD COAST

Drains under buildings
Drains may be laid under buildings with less cover than specified in Table 3.4. If the drain is under a concrete slab only 25mm of clearance is required from the top of the pipe to the bottom of the slab. Drains can pass under or through footings of concrete slabs or below ground walls as per Clause TAFE QUEENSLAND GOLD COAST

3.7.4 Drains under buildings
Drains below ground and under buildings may be laid with less than the minimum cover specified in Table 3.4, provided that— (a) 25 mm of overlay separates the drain from a reinforced concrete slab; or (b) the drain is adequately protected from mechanical damage. TAFE QUEENSLAND GOLD COAST

Proximity of other services
Clause 3.6 details the amount of separation and other requirements that must be provided around drains laid near underground services such as gas, water, communication and electrical installations. TAFE QUEENSLAND GOLD COAST

3.6 PROXIMITY TO OTHER SERVICES
3.6.1 General Where electrical conduit, wire, cable or consumer gas pipes, drains and other services are in existence, pipes shall be installed in accordance with the requirements of Clause to TAFE QUEENSLAND GOLD COAST

3.6.2 Separation from above ground electrical conduit, wire, cable, consumer gas or water pipes The separation shall be at least 100 mm between any discharge pipes and any aboveground— (a) electrical conduit; (b) electrical wire or cable; (c) consumer gas pipes; or (d) water services. TAFE QUEENSLAND GOLD COAST

3.6.3 Separation from underground electrical supply cables or consumer gas pipes (a) The separation between any underground drain and an electrical supply cable shall be at least— (i) 100 mm, provided the electrical supply cable is indicated along its length with orange marker tape complying with AS/NZS and is mechanically protected; or (ii) 600 mm where the electrical supply cable is neither indicated nor protected. TAFE QUEENSLAND GOLD COAST

(ii) 600 mm where the consumer gas pipe is neither indicated nor mechanically protected. NOTES: 1 Mechanical protection is provided by any of the following: concrete slabs, continuous concrete pour, bricks designed for protecting electrical supply cables. 18 AS/NZS :2003COPYRIGHT 2 For clearance from a communication cable, see Clause TAFE QUEENSLAND GOLD COAST

3.6.4 Separation from underground electrical earthing electrode
The separation between any underground drain and an electrical earthing electrode, for an electrical supply not exceeding 1000 V, shall be at least 500 mm. For an electrical supply exceeding 1000 V, the relevant regulatory authority shall be contacted for a ruling. TAFE QUEENSLAND GOLD COAST

3.6.5 Separation from underground communication cable
The separation between any underground drain and a communication cable shall be at least 100 mm. TAFE QUEENSLAND GOLD COAST

3.6.6 Separation from other underground services
The separation between any underground drain and any other service other than consumer gas piping, electrical communication service or water service shall be at least 100 mm or 300 mm from a stormwater drain exceeding DN 100 (see Figure 3.3). TAFE QUEENSLAND GOLD COAST

DIMENSIONS IN MILLIMETRES FIGURE 3.3 TYPICAL SHARED TRENCH

3.6.7 Crossover of underground services
Any underground drain crossing a service or any underground service crossing a drain shall— (a) cross at an angle of not less than 45°; (b) have a vertical separation of not less than 100 mm; and (c) be marked along its length for 1 m either side of the centre-line of the service with marker tape complying with AS/NZS laid 150 mm above the installed service. TAFE QUEENSLAND GOLD COAST

3.6.8 Clearance from underground obstructions
Drains shall be installed with sufficient clearance to any underground obstruction to protect the drain from physical damage and to permit repairs. The clearance shall be at least 100 mm. NOTE: For drains in proximity to footings and foundations, see Clause 3.8. TAFE QUEENSLAND GOLD COAST

Designing property drainage systems

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