Fire Code Standards

[rlondeen]

I am doing a feasibility model in WaterCAD for water service to a new residential development. My firm's SOP for fireflow is 1500 gpm per fire hydrant using two fire hydrants at the same time (totaling 3,000 gpm) for two hours while maintaining a 20 psi pressure. That standard has been passed around by word of mouth and no one knows where it originated. The local governing agency (county) does not specify fireflow requirements and TCEQ (Texas Commission on Environmental Quality) requires 1,500 gpm with 20 psi on top of regular flow.

My problem is that our current system at the new development cannot handle 3000 gpm for 2 hours on top of average flow, but it can handle 1500 gpm. So I need to justify using 1500 gpm against "its just the way we have always done it" unless there is a reason to why we do it that way.

I have looked at the IFC and the NFPA for anything further but they seem to line up close to TCEQ.

Am I missing anything?

 

[77JQX]

Our local fire authority requires 1,500 gpm (for 2 hours with 20 psi residual) from a single hydrant for (most) residential fire flow. If the residence is greater than 5,000 square feet, then the flow goes to 2,000 gpm, with the same duration and residual. This is on top of maximum day demand. I believe the fire authority is using the IFC to set these flows. Our internal policy (as a utility) is to satisfy the flow with the tank empty, and only those pumps equipped with a standby generator operating.

 

[rconner]

You may wish to refer to AWWA Manual M31 concerning distribution requirements for "combined" water supply and fire protection. While I guess I may not be "up" on the latest version, I think this standard essentially requires 6" minimum size piping in loops, 8" in dead ends, and even larger in now rather common specific high service areas. At an absolute minimum, I believe it is indicated 500 gpm is to be available (e.g. 250 tom from two 2-1/2 inch hydrant hose nozzles) along with normal delivery all while maintaining a 20 psi residual pressure in the main.
That being said, there can be greater local requirements, as well as ISO and insurance ratings etc. To consider, that may well look more favorably on greater flow capabilities of fire protection systems. There is actually also an "NFPA" forum you might visit, if you need more specialized information.

 

[bimr]

Check with the state insurance underwriter. The insurance underwriter is typically the organization that sets the fire flow standards:

http://www.isomitigation.com/downloads/ppc3001.pdf