Water Supply Distribution Systems Flashcards
Identify components of public water supply systems (466)
- Water supply source(s)
- Processing or treatment facilities
- Means of moving the water
- Water distribution and storage systems
Identify characteristics of private water supply systems (469)
Similar to public, but the water supply may be separated from public by a meter or check valve. Or may be from an on-site water supply such as a well or lake.
Explain water supply testing (477-480)
Inspectors from the fire inspection division, building department, or water department may analyze the water supply. May be performed periodically, when distribution system is altered/expanded, or when new applications for construction are made. Fire flow tests include static pressure, residual pressure, and the formulas and calculations used to determine available water from these tests. The tests determine the rate of fire flow available for fire suppression.
Calculations or graphical analyses from the tests provide the following:
- amount of water flow from individual hydrants
- water flow pressures
- quantity of water available at any pressure
- pressure available across a wide range of flows
Test results may help identify weak points in system, reveal a loss in carrying capacity of mains, reveal closed or partially closed valves.
Explain fire hydrant inspections (480-481)
Inspector will need to:
- operate a pitot tube and gauge (to determine fire flow from hydrant)
- calculate how much water is flowing from hydrant
- determine residual pressure required for the water distribution system when water is flowing from the system
- perform the test, adhere to test precautions, determine possible obstructions in system, and analyze results based on computations
Perform on annual basis
Hydrants should be inspected before the test begins
Describe how to use a pitot tube and gauge to take flow readings (481-482)
- Open petcock on pitot tube and verify air chamber drained, close petcock
- Edge blade into stream with small opening or point centered in the stream and held away from the hydrant butt or nozzle approx. 1/2 diameter of the opening. Pitot tube blade should be parallel to the outlet opening with the air chamber kept above the horizontal plane passing through the center of the stream.
- Check velocity pressure reading from gauge. IF needle is fluctuating, read and record the value located in the center between high and low extremes
- After test, open petcock and drain water before storing.
The 2-1/2” outlet should be used.
Name types of water sources. (466, 468)
Reservoirs: Lakes, reservoirs, ponds, rivers, streams, aquifers, wells, or springs
Suction Tanks
Pressure Tanks
Gravity Tanks
What methods are used to move water? (470)
Gravity system - water supply system that relies entirely on the force of gravity to create pressure and cause water to flow through the system. The water supply, which is often an elevated tank, is at a higher level than the system.
Direct Pumping System - water supply system supplied directly by a system of pumps rather than elevated storage tanks
Combination system - water supply system that is a combination of gravity and direct pumping. Most common type of municipal water supply system.
List types of water distribution systems (472-473)
Piping, water mains
- Primary feeders: large pipes aka arterial mains, widespread spacing. Supply smaller secondary feeder mains. Fire hydrants rarely attached directly to these mains
- Secondary feeders: intermediate popes connect with primary feeder lines to create a grid. Control valves can isolate each secondary feeder
- Distributers: small water mains that serve individual hydrants, commercial and residential consumers. May form an intermediate grid between secondary feeders. Or may be dead-end lines.
Storage Tanks
Control Valves
Backflow Preventers
What can an inspector learn from testing water supplies? (480)
Available fire flow, weak points in the system, reveal a loss in carrying capacity of mains, reveal closed or partially closed valves.
List the tools needed to perform a fire hydrant inspection (480)
- Notebook
- Gauging device for checking discharge outlet threads
- approved lubricant
- Small, flat brush
- Gate valve key
- Pressure gauge and a tapped hydrant cap
- Appropriate pitot tube and gauge
- Hydrant wrench
- Water Stream diffuser
List the physical laws from which the constant used in the flow test formula is derived. (482)
The constant 29.83 (0.0667766) is derived from the physical laws relating water velocity, pressure, and conversion factors.
Explain residual pressure
20 psi is the minimum required residual pressure, which is enough pressure to overcome friction inside any one of the following:
- short 6” branch pipe
- hydrant
- apparatus intake hose
The EPA and many state health departments require 20 psi minimum to prevent external ground surface water or other contaminants / pollutants from being draw into the distribution system at pipe connection points.
Pressure differentials can collapse a water main or create cavitation (implosion of air pockets drawn into fire pumps connected to system). A fire apparatus operating at a low system pressure may draw the entire capacity of the system at a location. If a discharge valve is turned off too quickly, a water hammer (sudden surge in pressure) can be transferred to the water main resulting in damage.
Describe the procedure to conduct a flow test. (485-486)
The test hydrant is closest to the location requiring the test results. The flow hydrant is where pitot gauge readings are taken. The test hydrant should be between the flow hydrant and the water supply source. The flow hydrant should be downstream from the test hydrant.
Water is never discharged from the test hydrant. A pressure gauge cap is placed on the discharge and the hydrant is fully opened.
- Locate personnel at test hydrant and all flow hydrants to be used.
- Remove hydrant cap from test hydrant and attach pressure gauge cap with the petcock in open position. Check other caps for tightness. Slowly open hydrant by turning operating nut several turns. Once air has escaped and a steady stream of water is flowing, close petcock and fully open hydrant.
- Record static pressure seen on gauge.
- Remove cap from outlet on flow hydrant(s). Check and record hydrant coefficient and actual inside diameter of orifice when using hydrant outlet or nozzle.
- Open flow hydrants and read and record pitot gauge reading of velocity pressures. Individual at test hydrant simultaneously reads and records residual pressure. If residual drops below 20 psi, reduce number of flow hydrants.
- Slowly close flow hydrant to prevent water hammer. Check for proper drainage, replace and secure hydrant caps. Report any defects.
- Check pressure gauge on test hydrant for return to normal operating pressure, then close hydrant. Open petcock valve to prevent vacuum on pressure gauge. Remove pressure gauge cap. Check for proper drainage, replace and secure hydrant caps. Report any defects.
Enough flow hydrants should be opened to drop the static pressure by at least 10%. May be dropped 25% for more accurate results.
What precautions should an inspector take when conducting water flow tests? (487)
Control pedestrian and vehicular traffic. Conduct test in busy areas at nonpeak hours. Notify water department official. Notify businesses in area to reduce number of false reports about water main breaks.
Wear protective equipment:
- Helmet
- Gloves
- Eye protection
- Reflective safety vests
Erect traffic safety signs on busy streets
Tighten caps on hydrant outlets not used
Do not stand in front of closed caps
Do not lean on top of hydrant
Do not flow water in freezing weather
Open and close hydrants slowly
Do not flow where drainage inadequate
Check downstream where water will flow
“When in doubt, do not flow”
What are some obstructions an inspector may encounter when conducting water flow tests? (489)
Encrustations
Sedimentation deposits
Malfunctioning valves
Malfunctioning pipes
Malfunctioning pumps
Foreign matter other than deposits
Increased friction loss
List the steps involved in a graphical analysis. (490)
- Determine which gpm scale to use
- Locate and plot static pressure on vertical scale at 0 gpm
- Locate total waterflow measured during test on chart
- Locate the residual pressure noted during the test on the chart
- Plot residual pressure above the total water flow measured
- Draw straight line from static pressure point through residual pressure point on water flow scale
- Read gpm available at 20 psi and record figure. This reading represents the total available water.
Public water supply distribution systems are usually a function of: (466)
A. fire departments.
B. local contractors.
C. local government.
D. state government.
C
What is the BEST method for evaluating the capabilities of a private water supply distribution system? (467)
A. Photographs
B. In-person inspection
C. Reviewing documentation
D. Interviewing the property owner
C
Which of the following is used to move water from treatment facilities to distribution and use points? (470)
A. Suction
B. Reservoirs
C. Pressure tanks
D. Gravity systems
D
A hydrant is a component of a water: (472)
A. supply source.
B. piping system.
C. distribution system.
D. secondary feeders system.
C
Which type of water main is small enough to serve individual fire hydrants? (473)
A. Distributors
B. Primary feeders
C. Secondary feeders
D. Combination feeders
A
Fire flow tests determine: (479)
A. the way a fire moves through a building.
B. the rate of fire flow available for fire suppression.
C. how many hydrants are needed on a residential street.
D. the optimum time period for fire suppression at a specific location.
B
To perform fire flow tests, an inspector must have the ability to: (480)
A. read a set of building plans.
B. operate a static pressure valve.
C. operate a pitot tube and gauge.
D. calculate the costs related to water use.
C
The easiest way to determine how much water is flowing from a hydrant outlet is to: (482)
A. review the historical documentation.
B. read the manufacturer documentation.
C. ask the municipal water department engineer.
D. refer to prepared tables for nozzle/outlet discharge.
D
Residual pressure can be defined as enough ____ to overcome friction in a hydrant, branch pipe, or intake hose. (484)
A. flow
B. pressure
C. differentials
D. available water
B
Which of the following precautions is crucial during a fire flow test? (487)
A. Traffic control
B. Re-directing pedestrians
C. Only conduct tests at peak hours
D. Minimizing damage to public and private property
D
