1. CPCPRF2003A Collect & Store Roof Water
This unit covers the competency to determine storage requirements and to plan, prepare and install storage tanks and related piping for roof water collection systems, for the collection of roof water.

2. CPCPRF2003A Collect & Store Roof Water
The factors that influence the design of a roof water collection and storage include:
• The intended use of the water;
• Drinking only;
• General house usage;
• Outdoor usage only;
• All or a combination of the above;

3. CPCPRF2003A Collect & Store Roof Water
The amount of water required is dependant on;
•The intended use, and the number of consumers;
• The available rainfall including;
• Quantity and distribution;
• The available roof area to capture the rainfall;

4. CPCPRF2003A Collect & Store Roof Water
The available area for tank location dependent on the;
• Land size and;
• Terrain;
• Tank to be above or below ground; and
• The tank materials used.

5. As studied previously in Work Effectively in the Plumbing Sector
Background
As studied previously in Work Effectively in the Plumbing Sector

6. Maslow identifies water as one of our most basic needs for survival
Background
Maslow identifies water as one of our most basic needs for survival
World health organisations all agree water is one of the primary drivers of public health.
We as plumbers are entrusted with helping to maintain the general health of the people of Australia by delivering safe drinking water

7. Background
In isolated country houses and some rural communities roof water has long been the potable source of water for drinking and household use.
Increasingly however, rainwater tanks are being installed to supplement the reticulated supply by providing water for gardens, swimming pools, toilet cisterns and some other indoor applications.
Definition
AS/NZS Drinking (Potable) water :
water which is suitable for human consumption, food preparation, utensil washing and oral hygiene.

8. Identify water storage system requirements;
Planning
To demonstrate competence in this unit you are required to provide sufficient evidence to prove your capability in the following areas:
Identify water storage system requirements;
Plan and prepare for installation;
Install storage system; and
Clean up.

9. Plans or specifications provide Location and details of installation
Planning
Some of the information sources you will use and the type of information each source can provide you with are.
Plans or specifications provide
Location and details of installation
Site inspections provide
Site layout and access
Hazard identification
Specific measurements

10. Regulations, standards, codes, guidelines Service location
Planning
Authorities provide
Work Permits
Regulations, standards, codes,
guidelines
Service location
Manufacturers provide
Material specifications and installation requirements

11. Company's quality assurance program provide
Planning
Company's quality assurance program provide
Standards and procedures
Weather bureau provides
Atmospheric exposure conditions.
Forecasts/warnings of bad weather.
Rainfall data

12. To determine the required tank capacity requires a number of steps
Calculations
To determine the required tank capacity requires a number of steps
The amount of annual rainfall for the area
The roof catchment area available
Water consumption requirements

13. To determine the annual rainfall from the following
Calculations
To determine the annual rainfall from the following
• The Bureau of Meteorology website
• AS/NZS Appendix E.
The land owners records

14. The Bureau of Meteorology website contains
Calculations
The Bureau of Meteorology website contains

15. To determine the roof area requires some calculations
Divide the area into suitable squares or rectangles as shown.
Area A = 5 m x 5 m
Area B = 10 m x 10 m

16. Add them up to arrive at the total area.
Area A: 5 x 5 = 25 m2
Area B: 10 x 10 = 100 m2
Total Area: 125 m2
These calculations are covered in detail in Section 3.4 of AS and Section of AS Either of these publications should be used to complete the class exercise.
The following example will assist you in this task.

17. Using the 125 sq m determined
To find the effective roof area:
Total roof area (100%) = 125 m2.
Loss factor due to wind and splashing = 30%
Effective roof area = 70% of total roof area
125 m2 x 70% = 87.5 m2.
In this example the annual rainfall on the roof is 600 mm (0.60 m) per year based on a property at Dubbo NSW.

18. Rainfall on a roof area:
= roof area (m2) x rainfall (m) x 70% (spray wind allowance)
= 125 (roof area) x 0.60 (rainfall) x 70% (splash allowance)
= 75 x .70
= m3 or 52,500 litres per year on average
NOTE: Remember this is a yearly average figure and does not account for seasonal variation and extended drought periods.

19. To determine water consumption requirements
The intended use and the number of users determine water consumption requirements.
The table on the next page shows average daily rate of water consumption in an isolated domestic supply and how this increases with the addition of more people.
Another factor that can significantly affect consumption is the water conservation culture of the household. People that have grown up with “unrestricted” supply may need to adjust their behaviour when relying on tank water.

20. Water consumption requirements The table shows that three people, in a household with a septic system, use only 320 litres per day (not 3 x 200) litres.
Number of persons
House with septic system
(Litres per day)
House without
septic system
(litres per day) 1
200
140 2
270 3
320
250 4
340 5
360
300 6
380 7
430 8
450

21. Water storage requirements
How much water needs to be stored you need to know how long water needs to be stored. This represents the length of time that can be expected without significant rain. In other words, if your tank is full and the rain stops, how long will it last.
To determine the capacity of a storage tank needed for a household,
Multiply the daily rate of water consumption by the number of months’ storage (in days), that must be catered for.

22. Water storage requirements cont.
Example
Using the table above calculate the water storage requirements for three months for four people in a household with a septic system.
Size of tank required (litres) = Daily rate (litres) x Minimum storage days
Daily rate = 340 litres / day
Minimum storage days = 3 mths x 30 days
= 90 days
Size of tank required = 30,600 litres

23. Water storage requirements cont.
Size of tank required to last 90 days = 30,600 litres
The 125 m2 roof provides 52,500 litres per year on average
This example has insufficient roof catchment to provide adequate water supply
Given that the minimum storage days are fixed there are two things that can affect the storage requirements.
1. Consumption can be reduced by changing habits to use less water
or by introducing a supplementary supply like a dam or bore.
2. The size of the catchment area can reduce the safety factor by making it more likely that the tank will be full when the dry period starts.

24. Gutters and downpipes Note
The sizes of gutters and downpipes must be large enough to accommodate and convey heavy downpours of rain to the storage tanks without losing valuable water because of overflows from the gutters.
You will normally be provided with this information, or they may already have been installed.
NOTE: CPCPRF3002A Fabricate and install roof drainage components addresses this topic in more detail.
Note
Sizes of gutters and downpipes must be calculated in accordance with AS/NZS Section 3 or SAAHB114

25. Plan and prepare for installation
Order materials
A typical list may include:
Tank support materials;
Tank;
Gate valve and fittings;
Stormwater pipe and fittings;
Gutter and fixings; and
Downpipe and fixings.
Materials for the collection of potable water must be carefully selected to avoid contamination of the water.

26. Installation Plan work with others Check materials Prepare work area
You need to consider how the task you are about to commence affects others and plan with this in mind.
Check materials
On delivery you need to check the materials to ensure that they are in good condition and what you ordered
Prepare work area
The worksite must be prepared before you start the installation process.
Carefully consider
OH&S precautions should be in place before work progresses;
Locating on-site storage for plant and material in convenient location for yourself and others;

27. Installation cont. You must check
All the details collected in the preparation stages need to be followed during installation unless a problem is identified.
You must check
Footprint of the support structure;
• Clearances from buildings and boundaries;
• Effect of excavation on existing or proposed structures; and
• Level of tank inlet with respect to gutter.

28. Installation cont. Above ground tanks
Should be located as much as possible in shaded areas to prevent the water heating, which can also promote algae growth
Advantages
Don’t require major earthworks and are generally quicker to install;
Don’t have to withstand “earth pressures” and can be lighter and cheaper in construction;
Can be raised to provide limited gravity pressure;
Leaks can be easily detected; and
Can be drained easily.

29. Installation cont. Disadvantages Take up valuable space;
Need to have suitable base constructed to support them;
Are exposed to weathering; and
May require tying down for times when the tank had little water.
Above ground tanks
Can be installed on the ground, on a slab or on a stand
Refer to your notes for details for on ground and slab

30. Elevated tanks
Stands can be used to both support an elevate tanks for additional pressure. The support structure must be designed to carry the full tank load.
NOTE: 1 litre of water weighs 1 kilogram.
1 000 litres (1 m3) weighs 1 tonne
Gravity feed system

31. Elevated tanks
With a gravity feed system, the higher the storage tank level, the greater the outlet pressure will be.
The head pressure or static head is calculated by measuring vertically the height of the water level above the outlet point.
For each 1 metre head of pressure, a pressure reading of 9.81 kPa can be obtained (approximately 10 kPa pressure from 1 metre elevation).
Note AS3500 requires a minimum pressure of 50kPa which is a minimum of 5.1m above the highest fixture outlet served.

32. A tank storage with a water level of 30 metres above the outlet point will produce a pressure of or approximately 300 kPa.

33. Below ground tanks
Below ground tanks need to be strong enough to withstand the pressures of being buried.
Advantages
Take up less garden space;
Keep water cool; and
Are well below the level of the gutter.
Disadvantages
That leaks and problems are not obvious and they are susceptible to contamination through ground water;
Can be damaged by tree roots;
If access is not restricted there is a risk of people or animals drowning in the tank;
Can be damaged by traffic;
If ground is water charged, and the tank is low it may “float”; and
Difficult to drain and clean.
Storage tanks must be handled with care because there is usually no way of testing them for leaks until the rains have filled them up.

34. Quality of water
Rainwater that has fallen on a roof catchment area surface is generally considered pure enough for potable use. However, where a reticulated supply is also available authorities may recommend that this supply be used for drinking.
Rain can be collected for potable supply from all metal based roof materials apart from lead or metal sheeting coated with lead based paints that can contaminate the water supply. Tiles, polycarbonate and fibre glass are also suitable.
Catchment area roofs must be kept clean and free from contamination. Roofs may become coated with dust, bird droppings, decayed vegetable matter (leaves, moss, weeds, etc) or other contaminants such as traffic or industrial pollution. Aerial spraying of insecticides and chemical fertilisers can also cause serious problems.
The use of a first flush device will assist in this area

35. First Flush Devices

36. Quality of water
Tanks should all have tops to prevent evaporation, contamination and algal growth.
Screens may also be installed to remove leaf and tree matter, surfaces. Meshes also keep out mosquitoes and small animals.
Tanks have to be installed below the level of the gutter. Overhead connection is desirable but underground mains are quite often the only alternative. In this case a minimum 0.5 metre difference is required so that gutters don’t overflow during heavy rain.
Downpipes and stormwater must also be watertight.

37. Typical installation
The overflow from tanks should be discharged to an area where they won’t cause damage to structures or erosion.