Part 2 Ch. 4-6 Water Supply Systems and Water Flow Analysis Flashcards
4 basic components of Water supply system
1 Supply source
#2 Treatment facility
#3 Mechanism for forcing water through system
#4 System of piping to transport water to community
Sources of Water Supply
- Surface water and ground water are the 2 sources most communities only use one or the other
- May be single or multiple sources, multiple recommended in case main source compromised
- Surface Water supplies
-Most common by far, Rivers, Streams, Lakes, Reservoirs, Coastal Water, Ponds
-Rivers and Streams most affected by rainfall
-Oceans and Coastal waters generally not used due to price and difficulty of removing salt
-Surface Water- softer, darker color, more bacteria, affected more by rainfall - Ground Water Supplies
-Wells and Springs
-Ground Water- Harder, clearer, less bacteria, less affected by rainfall
Water Treatment Facilities
- Involves 2 basic processes
1. adding elements to improve water
2. Removing contaminants - Contaminants can be removed by 4 basic processes
#1 Sedimentation- Gravity drops contaminants to bottom
#2 Filtration- Passes water through series of filters
#3 Coagulation- used in combination with other method, combines particles
#4 Chemical Treatment- remove or add elements to water
-Chlorine for removing bacteria
-Calcium/Magnesium as water softeners
-Oxygen and Fluoride for healthier drinking water
Water Distribution System
Pipes, Valves, Meters, and Hydrants
3 common designs piping arrangements
- Tree System
-Central primary supply pipe that feeds branches
-Primary disadvantage most places in system only receive water supply in 1 direction, or if break in system occurs everyone downstream of break lose -water supply
- Circle/Belt System
-Found in small and private jurisdictions
-Not common in municipal systems
-Common for secondary fire protection
- Grid Systems
-Most modern municipal water distribution system use this one
-Inter-looped system of pipes, a break in one area easily isolated with valves
-Primary Feeders (8-72”) = Largest pipes or mains carry water to smaller main
-Secondary Feeders (6-36”) = Loop off primary feeders
-Distributors= (4-20”) Smaller mains serving individual Hydrants and blocks of consumers
-Hydrant that is only supplied from one side known as Dead-End Hydrant
-Minimum 8” for any new pipes installs
- Pipe Material
-Installed underground
-Old systems use hollow wood
-Areas of corrosive soil or unstable use steel or reinforced concrete pipes
Fire Hydrants
2 Types (wet, dry)
- Dry Barrel-
-Used in areas were freezing waters common
-Valves sits above frost line keeping water under
-Be sure it drains after use in freezing condition
- Wet Barrel-
-Compression Valve at each outlet - All Hydrants –
-Have at least ONE large outlet (4 or 4.5”) along with TWO smaller outlets (2.5”)
-5” valve opening and 6” connection to water main
-Always look out for leaks, at main valve when closed, at drain valve when hydrant open but caps are in place, at water main near hydrants
Hydrant Color Codes
Class AA Light Blue 1,500 gpm or greater
Class A Green 1,000- 1,499 gm
Class B Orange 500-999 gpm
Class C Red less than 500 gpm
Private Water Supply Systems
- Most served by municipal systems
- 3 purposes are
#1 Fire Protection
#2 Sanitary/Consumption/Fire protection
#3 Manufacturing/Fire Protection - Served and separated by two systems beneficial but not cost prohibitive
Why Water Flow Analysis in Necessary
- Only true reliable method for determining amount of available flow at any chosen point in a distribution system
- To determine is system is operating as designed (closed valves/blockages can affect operations)
- To determine whether a properly functioning water supply system can provide adequate flow to target hazard in area
- Should be run at least every 5 years or after any significant alteration to mains
- Mathematical calculations not accurate for many reasons:
-sedimentation build-up
-closed valves
-changes over time
-changes at different locations
Water Supply Analysis Equipment
- For hydrant examination:
-Thread gauging device to check threads
-Can of lubricant oil to lube caps
-Flat brush to clean
-Gate valve key to check valves near hydrant
-Large Pail to hold debris moved from hydrant to dispose of later
-Hydrant Wrench
Flow portion of test requires; - To conduct flow portion of test:
-Static Pressure gauge= able measure pressure of at least 200psi
-Pitot tube gauge= measure at least 200psi.
-Hold the gauge approximately ½ the size of discharge away from the discharge during reading in center of opening. Record median of number if fluctuations present
3 components required for Performing Water Flow Analysis
- Determine available water supply
- Determine volume of flow from test hydrants
- Establishing required residual press.
Flow Test Analysis: Determining Available Water Supply
- Static pressure and residual pressures measured and used to calculate available water, Hydrant’s flow and press. can also be applied to determine flow at any pressure or vice versa
- If testing private water supply owner or representative should be present, at very least they should open and close valves to release Fire Dept from liability of damages
Flow Test Analysis: Flow test procedures
- First step is checking condition of hydrants- obstructions, etc. at least 15”, damage, rust, check draining by placing hand over outlet and feel for suction
When in doubt do NOT flow - Proper testing requires at least 2 hydrants
- Test Hydrant- calculations relevant to this hydrant, no water discharged. Must be located between water supply and flow hydrant (in MIDDLE). Opened and used static gauge to measure static pressure
- Flow Hydrant- Hydrant that is flowed to create pressure drop in test hydrant may be more than 1 flow hydrant. Open 2 ½ outlet and flow water record velocity pressure. Should open enough flow hydrants to cause at least a 10% pressure drop at test hydrant more accurate is 25% drop. Residual pressure should never drop below 20psi at TEST hydrant if it does hydrant OOS, or reduce number of hydrants open when using multiple flow hydrants. If flow pressure to low at flow hydrant add smooth bore nozzle. Shut off elevated storage tanks if near test site cause they’re not sustainable
Required(Necessary) Fire Flow
RFF/NFF
Important in determining if required amount of flow is even available and number of units responding to produce required GPM’s
Required Fire Flow for Manual Fire Fighting Operations Formulas
- 3 types formulas in use for over 60 years
-Iowa State Formula
-National Fire Academy Formula
-ISO Formula - Based of Fog nozzles pioneered by Glenn Griswold
- “Little drops of water” Chief Layman studies in Miami, KC, and Missouri
Required Fire Flow for Manual Fire Fighting Operations - Iowa State Formula
- Floyd Nelson and Keith Royer
- More than 60 years old and still widely used
- Worked to create a formula, they felt is was highly practical because if allowed RFF to be calculated for a structure before fire occurred
- One gallon of water will absorb all the heat that can be produced in 200 cubic feet
