Ch. 12 Water Supply
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- Normally buried or installed in utility manholes.
- If properly ind=stalled can be operated above ground through valve box.
- Some cases a special socket wrench on a reach rod needed to operate.
- Visually shows positions of gate or valve.
- Post Indicating Valve: Hollow metal post that houses valve stem. Has a plate that says open or shut.
- Outside Stem & Yoke (OS&Y): Has a yoke on the outside with thread system that opens & invisisble when closed.
What are the two types of water system valves used?
Indicating & Nonindicating
How often should valves be opened?
At least once every year to keep them working.
Why should valves be located at frequent intervals in a grid system?
So only small sections are cut off it is necessary to locate parts of the system for repairs.
American water works association recommended fire-hydrant supply mains
- 6" diameter in resedential.
- Closely gridded by 8" cross-connecting mains at intervals no more than 600'.
- 12" mains on priciple streets in the long mains but cross-connecting at frequent intervals.
How many primary feeders should be used for a sufficient water supply?
- Two or more primary feeders.
- Secondary feeders connect primary feeders & supply water from two directions to any point.
Grid System Components
- Primary Feeders: Large mains, widespread, large quantity of water.
- Secondary Feeders: Intermediate-sized mains that run from primary to distributors.
- Distributors: Grid of small mains serving fire hydrants & blocks of consumers.
What are hydrants that receive water from more than one direction called?
Circulating feed or looped line
What is a dead-end fire hydrant?
- A hydrant that receives water from only one direction.
- Has a limited water supply.
What does friction loss do to hydrants?
Reduces the volume & pressure of the water flowing to the hydrant.
What happens when water flows through pipe?
The movement causes friction & reduces water pressure.
A potential hazard with water treatment facility's is what?
They typically store large amounts of chlorine.
What happens if a water facility's pump goes down & there is an emergency?
If there is a fire it could reduce the volume & pressure of water available.
- Uses water source from a higher elevation than the distribution system.
- Pressure only adequate when source is more than 100' higher than the distribution center.
- Ex. Alpine lakes & mountain reservoirs
Direct Pumping Systems
- Mostly found in agricultural & industrial settings.
- One or more pumps move water from primary source to point if use.
- Disadvantages: Total dependence on pumps & electricity
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