How to Calc Upstream of Manual Standpipe FDC?

7/16/2026

When calculating manual standpipe systems per NFPA 14, are there any tips on calculating upstream from the FDC back through the hose lay back to the apparatus?

And I assume even considering the underground supply the apparatus is drawing from?

I know many pumper trucks are rated at 1,500 gpm at 150 psi, but I assume one would need to verify that, and what length, diameter, and type of hose they utilize from the truck to the FDC.

I see too many calcs that assume an "infinite" water supply if it is supplied by a pumper truck.

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4 Comments

Dan Wilder

7/16/2026 07:56:13 am

You'll need to talk with the FD as their SOP what "should" be a standard connection and what that includes (large diameter to a wye, individually fed smaller lines) then get the pressure losses through those hoses and fittings, then get the pumper truck ratings and put it all together.

I have never calc's from a hydrant to a truck to the FDC, the pumper truck "should" be the water supply.

Is this for the water supply or what the truck can provide for the FDC? Water supply goes more to the fire flow which is handled by Civil to prove (most fire flows, at their minimum allowable, are still 1000 GPM).

Check NFPA 1901 for pumper truck capabilities
Section 16.2.3.1 where a pumper truck is rated at 3000GPM or less, it shall provide the following:
100% of rated capacity at 150 PSI
70% or rated capacity at 200 PSI
50% of rated capacity at 250 PSI

While I work with mostly larger departments, I have yet to come across a pumper truck that could not meet a 1500 or 2000 GPM supply, meaning the residual pressures shown from above generally cover any manual FDC supply methods. I do ask the Fire Marshall for permission to use anything above the standard 150 PSI and we also provide signage at the FDC/Remote FDC as to the pressure required. Even with signage, the truck engineer will provide whatever his crew needs once inside (I am told)

Chad

7/16/2026 08:37:39 am

'the truck engineer will provide whatever his crew needs once inside (I am told)'

Sooo true. A good engineer will do the street math in their head and adjust for conditions on the fly. There is still a bit of intuition and experience required beyond what the book tells you.

Or the engine boss will holler at you if you are too high/low real fast.

Chad

7/16/2026 08:33:26 am

There are plenty of 1000/1250 GPM pumps out there, especially in cities with tight streets that can't order a 'normal' size platform. But 1500 is prototypical standard. 99% are less than 3000

Dan is right, some departments pump at 150 no matter what. Others have different guidelines, its not safe to assume. 99.99% of the time the truck is the water source when calcing from the FDC.

Anthony

7/17/2026 10:40:54 am

Calculating the hose friction losses are always difficult as finding a loss per ft is always hard. So many different brands and dynamic loss factors from bends and hose kinks. I usually use a sch 40 pipe with c100 of the size of input(2 1/2'' or 5'' hose) with several 90's for good measure.

I've been asked to calculate from the hydrant to the pumper then to the fdc as well to validate volumetic flows as well. I would urge you to be extra conservative in these instances also as fire departments wont let the pressure drop below 20psi at the truck.

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How to Calc Upstream of Manual Standpipe FDC?

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