Fire Hydrants and  5'' Hose

Different Ways Of Calculating Additional Water Available From A Hydrants

First Digit Method

Percentage Method

Fire Hydraulics

 
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NFPA 1002

 

Fire Apparatus Driver/Operator

Standard For Fire Apparatus Driver

Minimum job performance requirements for firefighters who drive and operate fire apparatus.

   

 

NFPA 1914

 

Testing FD Aerial Devices

Specifies minimum inspection and testing requirements for aerial devices to insure a minimum degree of safety for continued use.

Applicable to aerial ladders, platforms and water towers.

   

 

NFPA 1911

 

Fire Pumps

Service Tests of Fire Pump Systems on Fire Apparatus

Establishes site, environmental, and equipment requirements for proper pump system performance testing as well as frequency and procedures.

   

 

Water Availability From A Hydrants

 

                           

                                                Distribution Systems:

The three classes of mains are generally referred to as primary feeders,

secondary feeders, and distribution mains.

Primary Feeders

Primary feeders are large pipes that are used for moving water from the source of supply or storage area to the secondary feeders. The size of the primary feeders may vary from 48'' in larger cities to 12'' in smaller communities. If only one source of water is available, then a minimum of 2 primary feeders should be used to transfer water from the source of supply to the distribution system.

Secondary Feeders

Secondary feeders are smaller than primary feeders, but larger than the distribution mains used in the grid system. Secondary feeders tie the grid system to the primary feeders so as to aid in the concentration of the needed fire flow at any point within the grid network.

        Whenever possible, secondary feeders should be looped so that water is supplied to the distribution mains from two directions. Secondary feeders in well-designed systems should not be spaced more than 3000' apart.

Distribution Mains

        12'' mains are recommended on all principle streets, with 8'' mains cross-connected every 600' in business districts. The recommended minimum size for mains in residential area is 6''. These should also be cross - connected at intervals of not more than 600'.

Hydrants

Standards for hydrants are prepared by the AWWA. A standard hydrant is designed for a working pressure of 150 psi and is hydrostatically bench-tested at 300 psi. An installed hydrant with a single 2 ½ inch outlet should be capable of a flow of a minimum of 250 gpm with a pressure loss of not more than 1 lb between the street main and outlet. Those hydrants with two 2 ½ inch outlets should be capable of a flow of a minimum of 500 gpm with a pressure loss of not more than 2 lbs between the street main and the outlet. 4'' outlets should be capable of a minimum flow of 1000 gpm with a pressure loss of not more than 5 lbs between the street main and the outlet. It is also good practice to maintain a clearance around hydrants of at least 3 feet.

 

 

   CALCULATING ADDITIONAL WATER AVAILABLE FROM HYDRANTS

                                                               Percentage Method

When a pumper is connected to a hydrant and not discharging water, the pressure on the intake gauge is the STATIC PRESSURE.   After pumping begins discharging water, the intake gauge reading becomes the FLOW PRESSURE.  The difference between the static and flow pressure is known as RESIDUAL PRESSURE.   To calculate how much water is available, use the following formula:

                             Percentage Method

                     After determining the percent of decrease of pressure, use the following table:

 

% Decrease of Pressure                                              Additional water available

      0-10%                                                                        3 times the original amount

     11-15%                                                                       2 times

     16-25%                                                                        1 time

      >25%                                                                         less than original GPM

                                                                                        

Anytime multiple lines are used or a pressurized water supply is coming into the pump, the pressure relief device MUST be set.

The amount of water still available from a hydrant is determined by the difference between STATIC and RESIDUAL pressures.

1. 0 to 10% drop = 3 more like amounts

2. 11 to 15% drop = 2 more like amounts

3. 16 to 25% drop = 1 like amount

 

FIRST DIGIT METHOD:

1. Find the difference between static and residual pressures. (example: S = 90, R = 70, difference = 20  REMEMBER this number)

2. Use :                       and COMPARE

Multiply first digit of Static Pressure by 1  =9 3 more like lines
Multiply first digit of Static Pressure by 2  =18 2 more like lines
Multiply first digit of static Pressure by 3  =27 1 more like lines

 

If the psi drop is equal to or less than the first digit of the static pressure multiplied by (1), three additional lines of equal flow may be added.

If the psi drop is equal to or less than the first digit of the static pressure multiplied by two (2), two additional lines of equal flow may be added.

If the psi drop is equal to or less than the first digit of the static pressure multiplied by three (3), one additional line of equal flow may be added.

 

   

 

 

 

 

   

5'' Hose

 

Approx. FL per 100'

GPM 5'' HOSE
200 .28
250 .47
500 1.7
750 3.8
1000 6.6
1250 10
1500 14.5
2000 26

Relay pumping w/5'' Hose

Allow 20 psi on compound gauge in excess of the friction loss in the lines when pumping into another engine in relay. Relief valves should be set.

Ordinary water systems

are designed for maximum working pressure of 150 psi.

NORMAL hydrant flow pressures

are 65 psi to 75 psi

Hydraulic Gradient

is the PROFILE of residual pressure.

AWWA stands for

American Water Works Association - standards for hydrants. 

Hydrants are

designet for 150 psi working pressure and they are hydrostatically bench tested at 300 psi.

Hydrants should

deliver 250 GPM for each 2 1/2'' outlet

Hydrant Gate

is a valve connected to a hydrant doscharge outlet that allows control of the outlet independent of the hydrant discharge valve.

Tuberculation

deposits/sediments that accumulates in water main pipes.

High Pressure Hydrants

pressures vary between cities, normally from 160 psi to 180 psi and in some cities pressures range from 150 psi to 300 psi.

Minimum  flow pressure

from a hydrant is 20 psi, and for large mains is 10 psi.

Hydrant Markings

Red - flows less than 500 gpm

Orange - flows from 500 - 999 gpm

Green - flows from 1000 - 1499

Light Blue - flows from 1500 gpm

Hydrant Bonnet Markings

indicate main size:

Red - 4''

Yellow - 6''

Orange - 8''

Green - 10'' or bigger