1. Water & Water Supply Systems Sugar Land Fire Department Driver/Operator-Pumper Academy Spring 2003

4. Characteristics of Water –Is considered to be incompressible –Is measured in pounds per cubic foot –Is lightest close to its boiling point –Is generally considered to weigh 8.33 lb/gal or 62.5 lb/ft 3 –Is noncombustible –Can absorb large amounts of heat

5. Extinguishing Properties of Water –Can extinguish fire by cooling and smothering –Smothering works well on the surface of heavy flammable liquids and occurs to some extent when water converts to steam in a confined space –Heat absorbing capacity of water is affected by the Law of Specific Heat, The Law of Latent Heat of Vaporization, and by the amount of its surface area exposed to heat

6. Specific Heat –Specific Heat is a measure of the heat- absorbing capacity of a substance –Law of Specific Heat is the ratio between the amount of heat needed to raise the temperature of a specified quantity of a material and the amount of heat needed to raise the temperature of an identical quantity of water by the same number of degrees

7. Specific Heat –The specific heat of different substances varies –Amounts of heat transfer are measured in British thermal units (Btu) or in joules (J) (1 Btu = 1.055 kJ) –A Btu is the amount of heat required to raise the temperature of 1 pound of water 1*F –The joule has taken the place of the calorie in the SI heat measurement

8. Latent Heat of Vaporization –Latent heat of vaporization is the quantity of heat absorbed by a substance when it changes from a liquid to a vapor –Boiling point is the temperature at which a liquid absorbs enough heat to change to vapor –At sea level, water begins to boil or vaporize at 212*F (100*C) –Vaporization does not occur completely the instant water reaches the boiling point

9. Latent Heat of Vaporization

10. –One gallon of water will absorb 9346 Btu of heat if all the water is converted to steam.

11. Surface Area of Water

15. Specific Gravity –The density of liquids in relation to water is known as specific gravity –Water is given a value of 1. Liquids with a specific gravity less than 1 are lighter than water and therefore float on water. –Those liquids with a specific gravity greater than 1 are heavier than water and sink to the bottom.

16. Specific Gravity –If a liquid also has a specific gravity of 1, it mixes evenly with water. –Most flammable liquids have a specific gravity of less than 1.

17. Water Smothering Fire –Floating on liquids Water can smother fire when it floats on liquids that are heavier than water, such as carbon disulfide; however, if the material is water soluble the smothering action is not likely to be effective. –Forming an emulsion Water forms an emulsion over the surface of certain viscous combustible liquids.

18. Water Smothering Fire Agitation from the water spray causes the water to be temporarily suspended in emulsion bubbles on the surface of the viscous liquid. The emulsion bubbles smother the fire. The water in the emulsion also absorbs heat from the combustible liquid adjacent to it, reduces the liquid’s temperature, and decreases the amount of combustible vapors emitted.

19. Advantages/Disadvantages –Advantages Water has a greater heat-absorbing capacity than other common extinguishing agents. A relatively large amount of heat is required to change water into steam, thus allowing water to absorb more heat from the fire than other extinguishing agents. The greater the exposed surface area, the more rapidly heat is absorbed.

20. Advantages/Disadvantages Water converted into steam at 212*F occupies 1700 times its original volume, pushing heat and fire gases from the structure and cooling the fire area when it condenses. Water is plentiful and readily available in most jurisdictions

21. Advantages/Disadvantages –Disadvantages Water has a high surfaces tension and does not readily soak into dense materials. Water may be reactive with certain fuels such as combustible metals. Water has low levels of opacity and reflectivity that allow radiant heat to easily pass through it. Water freezes at 32*F, so it can dangerously coat equipment, roofs, ladders, and other surfaces. Water readily conducts electricity

22. Pressure v.s. Force –Pressure is defined as force per unit area, and may be expressed in pounds per square foot (psf), pounds per square inch (psi), and kilopascals (kPa) –Force is a simple measure of weight and is usually expressed in pounds or kilograms

23. Determining Force –One cubic foot of water weighs approximately 62.5 pounds. Because 1 sq ft contains 144 square inches, the weight of water in a 1 sq inch column of water 1 foot high equals 62.5 pounds divided by 144 sq in or 0.434 pounds –A 1 sq inch column of water 1 foot high therefore exerts a pressure at its base of 0.434 psi –The height required for a 1 sq inch column of water to produce 1 psi at its base equals 1 foot divided by 0.434 psi/ft or 2.304 feet; therefore, 2.304 feet of water column exerts a pressure of 1 psi at its base

24. Six Principles of Fluid Pressure –Fluid pressure is perpendicular to any surface on which it acts.

25. –Velocity—the speed with which fluid travels through hose or pipe. –Standard Atmospheric pressure—pressure exerted by the atmosphere at sea level

26. –Psig—pounds per square inch gauge –Actual atmospheric pressure—the psi above perfect vacuum, absolute zero –Psia—pounds per square inch absolute –Vacuum—any pressure less than atmospheric pressure –Prefect vacuum—absolute zero pressure –Head pressure—the number of feet that 1 psi raises a column of water

28. –Static pressure—stored potential energy available to force water through pipe, fittings, fire hose, and adapters –Static– at rest or without motion –Normal operating pressure—that pressure found in a water distribution system during normal consumption demands –Residual pressure—that part of the total available pressure not used to overcome friction loss or gravity while forcing water through pipe, fittings, fire hose, and adapters.

29. –Residual—remainder; that which is left –Flow pressure (velocity pressure)—that forward velocity pressure at a discharge opening while water is flowing –Elevation—the center line of the pump or the bottom of a static water supply source above or below ground level –Altitude—the position of an object above or below sea level –Pressure loss—Pressure when a nozzle is above the pump

30. –Pressure gain—Pressure when the nozzle is below the pump –Elevation Pressure—Both pressure loss and pressure gain –Friction loss—That part of the total pressure lost while forcing water through pipe, fittings, fire hose, and adapters.

31. Causes of Friction Loss –Movement of water molecules against each other –Inside surface of hose and piping –Hose couplings and pipe fittings –Bends, particularly sharp bends –Change in hose diameter or orifice by adapters –Improper gasket size –Piping control valves

34. Facts about Friction Loss –Hose size determines the velocity for a given volume of water. –The smaller the hose, the greater the velocity needed to deliver the same volume of water. –Friction loss in a system increases as the length of hose or piping increases.

36. –As velocity increases, the amount of flow decreases. –Decreasing the amount of water flowing, reduces water velocity in the hose and thus reduces friction loss –If stream velocity is increased too greatly, friction becomes so great that the entire stream is agitated by resistance. This agitation causes a degree of turbulence called critical velocity. –When critical velocity is reached, it becomes necessary to parallel or siamese hoselines to increase flow and reduce friction.

37. Methods of Reducing Friction Loss  Hose length  Hose diameter  Sharp bends (kinks) in the hose

38. Water Hammer –Water moving through a pipe or hose has both weight and velocity –The weight of water increases as the pipe or hose size increases.

39. –Always open and close nozzle controls, hydrants, valves, and hose clamps slowly to prevent water hammer.

44. Main Concerns of Water Systems –A maintenance error, natural disaster, loss of power supply, or fire disabling the pumping station(s) or severely hampering the purification process, thus reducing the volume and pressure of water available for fire fighting operations. –The inability of the treatment system to process water fast enough to meet demand, thus creating a shortfall

45. Water Distribution Systems –The water supply distribution system receives water from the pumping station and delivers it throughout the area served through a network of pipes. –When water flows through pipes, its movement causes friction that results in a reduction of pressure. –There is much less pressure loss in a water distribution systems when fire hydrants are supplied from two or more directions

48. Water Distribution Systems To ensure sufficient water, two or more primary feeders should run from the source of supply by separate routs to the community’s high-risk and industrial districts. Secondary feeders should be arranged in loops as far as possible to give two directions of supply to any point The recommended size for fire hydrant supply main in residential areas is at least 6 inches in diameter with cross-connecting 8 inch mains at intervals of not more than 600 feet

49. Water Distribution Systems In business and industrial districts, the minimum recommended size for fire hydrant supply main is at least 8 inches with cross connecting mains every 600 feet 12 in mains may be used on principal streets and in long mains not cross-connected at frequent intervals. Water mains as large as 48 inches may be found in major cities

50. Water Main Valves Valves function in a water distribution system to provide a means for controlling the flow of water through the distribution piping. Valves should be located at frequent intervals in the grid system so that only small districts are cut off if it is necessary to stop the flow at specified points Valves should be operated at least once a year to keep them in good condition Valve spacing should be such that only a minimum length of pipe is out of service at one time.

51. Water Main Valves A well-run water utility has records of the locations of all valves. If each fire company is informed of the locations of valves in the distribution system, valve condition and accessibility can be noted during fire hydrant inspections. An indicating valve visually shows whether the gate or valve seat is open, closed, or partially closed. Valves in private fire protection systems are usually of the indicating type

52. Water Main Valves Two common indicator valves are the post indicator valve (PIV) and the outside screw and yoke (OS&Y) valve. Post indicator valves are commonly used on private water supply systems OS&Y valves are most commonly used on sprinkler systems but may be found in some water distribution system applications. Non-indicating valves in a water distribution system are normally buried or installed in man holes

53. Water Main Valves Non-indicating valves are the most common types of valves use don most public water distribution systems Control valves in water distribution systems may be either gate valves or butterfly valves. If valves are installed according to established standards, it normally will be necessary to close off only one or perhaps two fire hydrants from service while in a single break is being repaired. All valves should be properly maintained and kept fully open

54. Water Main Valves High friction loss is caused by valves that are only partially open. When valves are closed or partially closed, friction loss may not be noticeable during ordinary domestic water flows. A fire department will experience difficulty in obtaining water in areas where there are closed or partially closed valves in the distribution system.

55. Water Pipes Water pipe that is used underground is generally made of cast iron, ductile iron, asbestos cement, steel, plastic, or concrete. When water mains are installed in unstable or corrosive soils or in difficult access areas, steel or reinforced concrete pipe may be used to give the strength needed.

56. Water Pipes Encrustation of minerals on the interior surfaces of the pipe and/or sedimentation that settles out of the water result in a restriction of the pipe size, increased friction loss, and a proportionate reduction in the amount of water that can be drawn from the system.

57. Consumption Rates  Average daily consumption (ADC)  Maximum daily consumption (MDC)  Peak hourly consumption (PHC)

58. Private Water Systems  To provide water strictly for fire protection purposes.  To provide water for sanitary and fire protection purposes  To provide water for manufacturing processes and fire protection