Is Building Fire Pump Size Affected by Firetrucks?

3/29/2024

For multi family buildings, I am being told that for a 4-story building, normally the fire pumps are only 15HP because the standpipes are pressurized by the fire trucks.

My understanding of NFPA 20 is that it would still be required to have a correctly sized fire pump without considering the size of the pump on the local fire trucks.

Is this an industry norm that is allowed by certain AHJ’s or is there code related to multi family that I am missing?

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11 Comments

Joe Burtell

3/29/2024 08:13:25 am

If the standpipes are a manual standpipe per NFPA 14, city water pressure is all you need, no fire pump. The FD is responsible to provide the flow and pressure needed, pumper truck. You still need to calculate the manual standpipe. If the standpipes are required to be fully automatic, you will need a fire pump sized to provide the full pressure and flow.

Dan (WSFP) Wilder

3/29/2024 08:33:39 am

I've not done a design that changed that because of it being specifically Multi-Family UNLESS if fell outside of the scope of NFPA 13R (above 60' or more than 4 stories) as the hydraulic requirements change.

It doesn't state how to provide the needed flows and pressures based on the applicable codes & standards (with any adoptions), just that those requirements need to be met. Height, locations, pipe sizing, pipe material, fittings, sprinkler all play into the final requirements then it's up to the MFG for equipment needs.

The smaller pump sizing is typically due to not needing a large fire pump to accommodate what is typically a small deficiency to get the sprinkler design to work and the lesser available incoming power and space requirements (for electric pumps) in lieu of a diesel pump but again, not limited to a specific HP.

Dan Wilder

3/29/2024 08:38:01 am

and since I've read this a couple different ways

The sprinkler system calculation can have a different supply than the standpipe calculation. It is not uncommon to have a city water supply (with or without a booster pump) for the sprinkler calculation, and another standpipe calculation based on the location of the FDC and AHJ fire pump apparatus providing the water supply (typically dictated by NFPA 1901). This applies to both residential and commercial buildings types.

Jesse

3/29/2024 08:40:13 am

If the standpipe is a manual standpipe as defined in NFPA 14, then the fire pump (technically a booster pump unless being supplied by a static source) is only serving the automatic sprinkler system. Most of the stand-pipes my company designs are manual standpipes. Effectively we use the fire department apparatus as the water supply node.

Anthony

3/29/2024 08:40:40 am

THe building's fire pump won't be affected by the city's fire truck.

The building STANDPIPE system may be. See A.7.10.1.2 from NFPA14-16 for reasonable Fire pump design curves when you don't know the pumper trucks information.

Jack G

3/29/2024 06:27:46 pm

Far from towns , buildings protected with sprinklers, would need its own tank, ( hose streams not required to be included- unless building has hoses) fire pump and standpipe hydrant with fdc.
The fire department usually has a pumper truck ( capable of flowing 750- 2500 gpm) with a tank, usually around 6000 gallons.
Other than that- if a building is protected by sprinkler system, and needs standpipes, in some cases the standpipe can be manual, where the fire truck connects to a city hydrant, and pumps the required pressure and flow to the building.( including sprinklers)
The installed sprinklers could work/ calculated off city pressure ( no fire pump in building) or a fire pump added to reduce pipe sizes ( buildings now a days are pretty tight above the ceiling)
So not much correlation between pumper trucks and building pumps)
Opinion.

RUSSELL BYRD

3/30/2024 12:15:03 am

The FDC piping for sprinklers and/or standpipe would be on the system side of the fire pump and be isolated by a check valve, which would close and cause the fire dept pumper to bypass the building fire pump...

Casey Milhorn

4/1/2024 09:27:15 am

As Russell stated, the FDC piping will be AFTER the fire pump discharge and it's not unnormal to have a 4" (or smaller) city water supply feeding a small 13R type pump setup but then have a 4" or 6" FDC piping system from FDC to standpipes. Think about it as the city is suppling your automatic sprinkler systems (with a booster pump when necessary) and the FDC system is supplying your standpipes/hose valves by way of pumper truck. They just happen to be partially a shared system.

Joe Burtell

4/1/2024 09:52:09 am

The problem I see here is the 2021 IBC does not allow 13R for buildings more than 30 above FDC access. If the building was not that tall we would not be talking about a standpipe system in the first place. See section 903.3.1.2 of the 2021 IBC. Maybe this jurisdiction has a different building code.

Glenn Berger

3/30/2024 07:14:03 pm

The fire pump provided for a building is not affected by the size of the pump on the truck.

The size of the fire pump is only affected by the requirements of fire protection systems provided for the facility.

The size of the fire pump may also be affected by the water supply system characteristics.

Robert bennett

4/3/2024 01:08:53 pm

Additional comment to Joe Burtell, I agree with your comment with one additional observation and that is that the standpipe must still be flow tested and provide the required VOLUME prior to occupancy. Over the past 5 years we have required flow testing as indicated in NFPA 14-19 and found that 30% of standpipes, hydraulically designed failed to flow the required volume at the designers specified pressure. I would strongly recommend that you work with your local FD to test the standpipes under operational conditions to insure they will function when needed.

We are a large department with 30 stations and the testing process provides good training for new pump operators and also forces the first due companies to visit and become familiar with the building layout.

RJB

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Is Building Fire Pump Size Affected by Firetrucks?

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