8 Water Supply Distribution Systems Flashcards
Two basic types of water supply systems
Public,
private
For components of an effective public water supply distribution system
Water supply source.
Processing or treatment facility.
Means of moving water.
Distribution system, including storage.
Primary source of water in North America
Groundwater
Layers of porous rock the capture groundwater and retain it
Aquifer
Three methods for moving water through the system
Gravity. Direct pumping. Combination
Water pressure caused by the source being at elevation
Elevation head pressure
Interlocking network of water mains the compose a water distribution system
Grid, or grid iron
Arterial Water mains beginning at 16 inches and exceeding 72 inches
Primary feeders
Intermediate water pipes that interconnect with the primary felines to create a grid 12 to 14 inches in size
Secondary feeder
Small water mains, 6-8 inches in diameter, that serve individual fire hydrants and commercial/residential customers. May form intermediate grid or dead ends
Distributors
Minimum size pipe often used
8 inches, although 6 inches is used in some subdivisions
Gravity tanks are used for
Maintaining and ensuring constant water pressure
Device used to control or interrupt the flow of water to individual hydrants or properties
Control valve
How often should control valves be exercised
Once a year
Maximum spacing for water control valves and high-value districts
500 feet
Maximum control valve spacing in other areas that arent considered high value
800 feet
Control valve for water distribution systems are probably divided into
Indicating, nonindicating
Two common indicator type valves
Post-indicator valve PIV
Outside stem and yoke valve OS&Y
A partially closed valve would not be noticed during normal water usage however during fire suppression operations it would be noticed because
High friction loss would reduce quality of water available
A valve that prohibits water that may be contaminated, from flowing back into public water system
Backflow preventer
Advantage of a wet barrel system
All working parts located above grade for easier maintenance and use
Disadvantage of wet barrel hydrant
Cannot be using claimant susceptible to freezing
Size of the large outlet on a hydrant often referred to as the pumper outlet nozzle or steamer connection
4, 4 1/2 inches
Hydrant discharge outlets are considered standard if they contain the following two components
4-4 1/2 inch main outlet, two 2.5 inch couplings
Hydrant specifications require what size valve opening for standard three-way hydrants
5 inches
Hydrant specifications require what size connection to the Watermain
6 inches
How often should hydrant inspections occur
Twice a year
Generally the barrel of the fire hydrant is painted chrome yellow for municipal hydrants and what color for private hydrants
Red
The use of violet to designate hydrants is done in the case when
Non-potable water supply has been established
Light blue indicates what class and fire flow of hydrant
AA CLASS
1500 gpm or more
What class and fire flow is a green hydrant indicate
Class A
1000-1499 gpm
What class and gallons per minute flow does a orange hydrant indicate
Class B. 500-999 GPM
What classification and fire flow is a red-indicate
Class C 500 GPM
Private water supply distribution systems are most commonly found on
Large commercial industrial or institutional properties
In general private water supply distribution systems exist for one of the three following purposes
Fire protection purposes.
Sanitary and fire purposes.
Manufacturing and fire purposes
Private water supply distribution systems commonly receive their water from
Municipal supply
Almost all private water supply distribution systems maintain what for private fire protection and domestic or industrial services
Separate piping for each
Many significant fire losses can be traced to
Failure of private water supply systems being used for firefighting
Mand open lake or pond or enclosed truck are similar to a tank used as a water source
Reservoir
Tanks located at ground level and provide a water supply source for pressure increasing fire pumps. Capacities typically from 100,000-300,000 gallons
Suction tanks
Pressure tanks usually range in size from
3000-9000 gallons
Gravity tanks are used to
Stabilize or balance water pressure at times of peak demand
Gravity tanks that are 100 feet high generate a pressure of only
43 PSI
Gravity tank capacity ranges from
5000-500,000 gallons
Small structures that contain standpipe connections and a large hoseline pre-connected to the discharge outlet
Hose houses
Pressure remaining at any given point in the water supply system while water is flowing
Residual pressure
Fire flow test of water supply systems include what pressures
Static and residual pressure
When should flow test be done of a water main systems and hydrants
After extensive improvements.
Construction of water line extensions.
Every five years
Although fire hydrants on private water supply systems are the responsibility of the property owner, inspector should still
Witness the hydrant test
Materials needed to complete inspection of fire hydrant
gauge for checking discharge outlet threads (female coupling) Lubrication Gate valve key Pressure gauge in hydrant cap Pitot gauge 12 quart Pail Stream diffuser
The clearance between the bottom of the butt (discharge) of the hydrant and the great should be at least
15 inches
A pitot gauge should be held in the center of the screen with a small opening or point centered and approximately how far from the opening
One half the diameter of the opening.
That’s 1.25” for a 2.5 “ discharge
Generally 2.5 inch outlets should be used to conduct hydrant flow test because streams of the larger outlet are
Contain voids in the stream
20 PSI residual pressure can be defined as enough pressure to overcome friction inside anyone of the following
Short 6 inch branch pipe.
Hydrant.
Apparatus intake hose
20 PSI minimum residual pressure is often required by the EPA for health reasons because
It prevents contaminants from external sources from being drawn into the system
Hydrant from where A pitot or cap gauge is used to find static and residual
Test hydrant
Hydrant from which water is discharged in a fire flow test is done
Flow hydrant
Flow hydrant should be located how in reference to the test hydrant
Downstream
A strong probable flow may require several hydrants be open to ensure accurate results. And of hydrants should be open to drop the static pressure by at least
10%. And a 25% should more accurate results be required
Growth crust or lump corrosion on the inside walls of water mains can reduce the diameter of the pipe and lower capacity
Encrustations
Encrustation is caused by
Chemicals Organism or bio growth Degradation of pipe materials Rust deposits Salt accumulated Bioreactor a from organisms in water
Sedimentation deposits are
Mud Clay or leaves
Foreign matter like rocks tools woods or lead
Two ways to compute fire flow test results
Graphical analysis, mathematical computation
Size of primary feeders
16-72”
Size of distributors
6-8”
Size of secondary feeders
12-14”
