06-15-2008, 07:53 AM #26
- Join Date
- Dec 2007
Water supply testing for fire department use is an important step in the prefire planning process for a building and or community. Low water pressure during a fire usually means the FD has exceeded the capacity of the water supply system. If the water supply can only supply 1200 gpm @ 20 psi or even 0 psi then that is it. If you place an engine that can pump 1500 gpm on a water supply that can only provide 1200 gpm then will have low water supply pressure as you have exceed the capacity of the water supply.
40% of the ISO rating is based on the town/city water supply.
Knowing how to test and evaluate a water supply is something all fire departments should know how to do. After all it is the the media we use to control and extinguish a fire.
Here is a good document on how to conduct a fire hydrant water supply test.
Also take a look at NFPA 291, Recommended Practice for Fire Flow Testing and Marking of Hydrants. If you do not have the latest NFPA codes and need to research the codes, here is link below. You can read BUT not print any NFPA code/standard.
Click on the code you want (NFPA 291)
Then go to the bottom of the page and click on "Preview this document".
Then click I agree
Then click on the code you choose at the bottom of the page.
Here is a link for 1.85 graph paper to plot your water supply test and to figure out how much you have at 20 psi or what ever flow pressure you desire.
Here is a link to a free hydraulic calculator to determine fire flow.
Here is a link for a company that sells all the equipment you will need to do a test, pitot, butt cap and gauges
If you have any questions let me know.
If you are in NJ take a look at a 1 day seminar this company does on water supplies for fire protection, Module 1. You conduct a water supply test and calculate the required fire flows.
Last edited by InsuranceLCRep; 06-15-2008 at 08:48 AM.Fire Sprinklers Save Firefighters’ Lives Too!
06-17-2008, 02:21 AM #27
- Join Date
- Jun 2005
It is a typical probie mistake to think that a 1250gpm engine can only flow 1250gpm when operating on a pressurized water source. Your flow is restricted by how much water you can put into your pump and how much you can get out. The pump piping has a greater impact on flow rates than the rated pump capacity (which is calculated at a draft.)
My company has flowed 2000gpm (1000gpm to engine mounted master stream and 1000gpm to an eleveated master stream) through a "1250gpm" pump. We had a good hydrant on a 16" main, hooked up to both 4 1/2" discharges with 5" supply lines, had a static of 100psi. We hooked the ladder to our lower LDH discharge (this pump discharge only feeds the one outlet) and flowed our master stream (this discharge pipe is shared with our second LDH outlet, had we flowed the ladder with this outlet our gpm output would have been lower.) The pump's capacity of 1250gpm had nothing to do with our ability to flow water. (We only lost 10% of our static pressure during the evolution so we have more water to spare.)
I wonder if our ol' 1950 Maxim 500pgm pump can pull off the same layout...
Last edited by lexfd5; 06-17-2008 at 02:22 AM. Reason: made mistake
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