Code Reference for Minimum Water Supply?

7/22/2019

Have a current project that is stalled due to water supply conditions. A water flow test was not conducted early in the project.

Options have been presented to the other responsible parties for consideration, however a particular party has rebutted with “Where does it say you can not go below a certain water pressure?” The existing water supply would be taken down to 6 psi and the questioning party wants documentation on the standards of the lowest psi a water supply needs or should not drop below.

Can anyone provide or give direction on finding information regarding water supply requirements or standards which address minimum water supply requirements?

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7 Comments

Rusty Scott

7/22/2019 10:21:52 am

Typically AHJ requires the water system to not be drawn past 20 psi. A low suction control valve is often used to control this when you are close. An article that I think helps under stand the idea is below. I believe it is the water system's company provider who is the one that makes the final determination on what the limiting psi is, I would check with them. I think most would agree that the FP industry standard is 20 psi in the minimum. Sounds like you need a water storage tank/vault.

https://www.csemag.com/articles/nfpa-20-changes-to-the-standard-on-fire-pumps/

Douglas E. Colter

7/22/2019 10:34:18 am

This is one of those questions you have to scratch your head on, because they should not be asking it, and it is not necessarily in the building codes. And Uh, Duh, why are they asking it? The building systems have to work!!!

The Fire Protection System is required to be engineered to meet the fire demand, and the math has to work to make the water flow, and that includes the input parameters for pressure and flow.

If you don't have the pressure but you have the flow, you put in a pump. If you don't have the flow, you put in a reservoir/tank and a pump.

On the domestic side, plumbing fixture manufacturers design their products to work within certain pressure/flow parameters. The code requires you to follow the manufacturer's instructions--a general principle throughout ICC and NFPA codes--and that is one code path to minimum delivery standards.

local Zoning regulations often have wording that requires minimum utility service standards to permit development. In one municipality I worked in, they required underground firefighting reservoirs for all new development where the public utility pressure was under 40 PSI

Health Department regulations may also address minimum water standards.

The Water Utility may also have minimum delivery standards, and require you to pay for system upgrades to provide the minimum.

James Phifer

7/22/2019 11:06:22 am

From NFPA 24: Appendix C;
C.4.1.3 It is generally recommended that a minimum residual
pressure of 20 psi (1.4 bar) should be maintained at hydrants
when delivering the fire flow. Fire department pumpers can be
operated where hydrant pressures are less, but with difficulty.

Mike

7/22/2019 03:09:50 pm

Taken down to 6 psi at your required flow?

What is your estimated flow and pressure demand?

John Kupcha

7/22/2019 04:56:12 pm

Water Pressure: The New York State Department of Health standard indicates that normal water pressure in the distribution system should be approximately 60 to 80 psi and not less than 35 psi while maintaining a minimum pressure of 20 psi under all conditions of flow.

Laura

7/23/2019 10:17:46 am

NFPA 1, Table 18.4.5.2.1, has requirements for fire flow, and these are to be available at 20 psi per the dagger footnote. See Section 18.4 for applicable reductions based on your building. There is the possibility that the required fire flow is less than your sprinkler system demand, but it is a straightforward reference to 20 psi that may be helpful to you.

Ed Berkel

8/28/2019 03:22:22 pm

I think most fire departments utilize the 20 psi; however, it is my understanding from our water purveyor that the Clean Water Act doesn't allow them to design below 35 psi

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