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Water Supply3-2
Characteristics of Water
• Compound of two parts hydrogen and one part oxygen (H20)
— Liquid between 32F and 212F (0C and 100C)
— Solid below 32°F (0C)
— Gas above 212°F (100°C)
• Incompressible
• Weight for fire protection purposes=62.5 lb/ft3 or 8.33 lb/gal (1 kg/L)
Water Supply3-3
Extinguishing Properties of Water
• The law of specific heat: the specific heat of any substance 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.
(Continued)
Water Supply3-4
Extinguishing Properties of Water (cont.)
• The law of latent heat of vaporization— The latent heat of vaporization is the quantity of
heat absorbed by a substance when it changes from a liquid to a vapor.
— 1 gallon of water will absorb 9,346 Btu (1,266 + 8,080) of heat if all the water is converted to steam.
(Continued)
Water Supply3-5
Extinguishing Properties of Water (cont.)
• Surface area of water: the speed with which water absorbs heat increases in proportion to the water surface exposed to the heat.— Expansion ability
— Smothering ability(Continued)
Water Supply3-6
Extinguishing Properties of Water (cont.)
• Specific gravity: the density of liquids in relation to water — Liquids with a specific gravity less than 1 are
lighter than water and therefore float on water.
— Most flammable liquids have a specific gravity of less than 1.
Water Supply3-7
Water’s Advantages as an Extinguishing Agent
• Greater heat-absorbing capacity
• Large amount of heat required to change water into steam
• Easily expanded surface area
• Plentiful supply
Water Supply3-8
Water’s Disadvantages as an Extinguishing Agent
• High surface tension
• Reactivity
• Low levels of opacity and reflectivity
• Freezes at 32F (0C)
• Conductivity
Water Supply3-9
Water Pressure and Velocity
• Pressure: force per unit area on a liquid or gas expressed in psi or kPa
• Force: simple measure of weight
• Velocity— The speed at which fluid travels through hose or
pipe
— Result of pressure exerted on the fluid at its source
(Continued)
Water Supply3-10
Water Pressure and Velocity (cont.)
• Principles of pressure— First Principle: fluid pressure is perpendicular to
any surface on which it acts.
— Second Principle: fluid pressure at a point in a fluid at rest is the same intensity in all directions.
— Third Principle: pressure applied to a confined fluid from without is transmitted equally in all directions.
(Continued)
Water Supply3-11
Water Pressure and Velocity (cont.)
• Principles of pressure— Fourth Principle: the pressure of a liquid in an
open vessel is proportional to its depth.
— Fifth Principle: the pressure of a liquid in an open vessel is proportional to the density of the liquid.
— Sixth Principle: the pressure of a liquid on the bottom of a vessel is independent of the shape of the vessel.
(Continued)
Water Supply3-12
Water Pressure and Velocity (cont.)
• Types of pressure— Atmospheric pressure: pressure exerted on the
earth by the atmosphere itself
— Head pressure– Height that a pressure can lift a column of liquid
– Height of a water supply above the discharge orifice is called the elevation head.
— Static pressure: stored potential energy available to force water through pipe, fittings, fire hose, and adapters
(Continued)
Water Supply3-13
Water Pressure and Velocity • Types of pressure (cont.)
— Normal operating pressure: 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
— Flow pressure (velocity pressure): forward velocity pressure while water is flowing
Water Supply3-14
Pressure Loss and Gain• Elevation
— Center line of the pump or the bottom of a static water supply source above or below ground level
— Elevation pressure results from differences in elevation of nozzle and pump.
• Altitude— Position of an object above or below sea level
— Effects of lower atmospheric pressure on drafting above 2000 feet (600 m)
Water Supply3-15
Friction Loss
• That part of the total pressure lost while forcing water through pipe, fittings, fire hose, and adapters
(Continued)
Water Supply3-16
Friction Loss (cont.)
• Causes— Movement of water molecules against each other
— Linings in fire hose/inside surface of piping
— Hose couplings/pipe fittings
— Sharp bends
— Change in hose size or in orifice by adapters
— Improper hose-coupling gasket size/pipe control valves
Water Supply3-17
Friction Loss (cont.)
• Principles of friction loss:— First principle: if all other conditions are the same, friction
loss varies directly with the length of the hose or pipe.
— Second principle: when hoses are the same size, friction loss varies approximately with the square of the increase in the velocity of the flow.
— Third principle: for the same discharge, friction loss varies inversely as the fifth power of the diameter of the hose.
(Continued)
Water Supply3-18
Friction Loss
• Principles of friction loss (cont.):— Fourth principle: for a given flow velocity, friction
loss is approximately the same, regardless of the pressure on the water.
• Other factors affecting friction loss: diameter and length of hose or pipe
• Reducing friction loss
Water Supply3-19
Water Hammer
• Energy surge that results from suddenly stopping or starting water moving through hose or pipe
• Can damage the pump, appliances, hose, or the municipal water system itself
Water Supply3-20
Municipal Water Supply Systems
• Components— Source of water supply
— Means of moving water
— Water processing or treatment facilities
— Water distribution system, including storage(Continued)
Water Supply3-21
Municipal Water Supply Systems (cont.)
• Sources of water supply— Public water supply system
— Surface or ground water
• Means of moving water— Directing pumping system
— Gravity system
— Combination system(Continued)
Water Supply3-22
Municipal Water Supply Systems (cont.)
• Water processing or treatment facilities— The fire department’s main concern regarding
treatment facilities is that a maintenance error, natural disaster, loss of power supply, or fire could drastically reduce the volume and pressure of water available for fire fighting operations.
(Continued)
Water Supply3-23
Municipal Water Supply Systems (cont.)
• Water Distribution System— Dead-end hydrants
— Circulating feed or looped lines
— Grid system– Primary feeders
– Secondary feeders
– Distributors
Water Supply3-24
Water Distribution System Variables
• Piping materials
• Pipe diameter
• Piping arrangement— Simple loop
– One inflow point and one outflow point.
– Exactly two paths between the inflow and outflow points.
(Continued)
Water Supply3-25
Water Distribution System Variables
• Piping arrangement (cont.)— Complex loop (grid)
– More than one inflow point
– More than one outflow point
– More than two paths between inflow and outflow points
(Continued)
Water Supply3-26
Water Distribution System Variables
• Piping arrangement (cont.)— Valves
– Function in system
– Location in system
– Access
– Indicating
– Nonindicating
– Gate valves
– Butterfly valves(Continued)
Water Supply3-27
Water Distribution System Variables
• Piping arrangement (cont.)— Hydrants
– Dry-barrel and wet-barrel
Water Supply3-28
Water Distribution System Variables
• Piping arrangement (cont.)– Distribution and location
– Maintenance
– Color coding:
Less than 500 gpm: Red
500999 gpm : Orange
1,0001,499 gpm: Green
1,500 gpm or more: Light Blue
Water Supply3-29
Private Water Supply Systems
• Purposes— To provide water strictly for fire protection
purposes
— To provide water for sanitary and fire protection purposes
— To provide water for fire protection and manufacturing processes
• Potential problems for fire fighting purposes(Continued)
Water Supply3-30
Private Water Supply Systems (cont.)
• Water supply requirements for standpipe and hose systems— NFPA 14, Standard for the Installation of
Standpipe and Hose Systems
— Class I service
— Class II service
— Class III service(Continued)
Water Supply3-31
Private Water Supply Systems (cont.)
• Water supply requirements for automatic sprinkler systems— NFPA 13, Standard for the Installation of
Sprinkler Systems
— Pipe schedule systems
— Hydraulically designed water-based extinguishing systems
(Continued)