Provide a 750 or 1,000 GPM Pump for Standpipes?

8/22/2023

I have a standpipe demand of 750gpm. I am providing a fire pump for the system demand.

Should I be selecting a 750 gpm pump or a 1000 gpm pump, based on adding a safety factor (or other reasoning)?

My sprinkler demand is less than 750 gpm so I would only need to provide the 750 gpm for the standpipes. Thanks in advance.

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10 Comments

Pete H

8/22/2023 07:22:27 am

750 is probably fine.

A pump can operate to 150% of rating along the curve.

There's additional flow coming from the water source before the pump, and it has to be decent enough flow to be able to supply a 750 or 1000 gpm pump for you to ask this question.

Anthony

8/22/2023 07:29:55 am

Assuming you only have 2 standpipes, 750 will be fine. Run a calc. Standpipe calc's can be done in excel. Select a pump with enough pressure to overcome the friction loss. You shouldn't have overflow problems with 3 flowing hose valves.

Dan Wilder

8/22/2023 08:03:12 am

At 750 GPM (assuming this is required to be an automatic standpipe), no issue at all as that covers both your sprinkler and standpipe demands, just watch out for overpressure issues on the lower floors. 13'-22 19.1.6.3.1 allows omission of inside hose allowances with a combined sprinkler/standpipe within fully sprinklered building and a Class I or III standpipe so even with a sprinkler demand close to 750 or slightly over, the water supply becomes the mitigating factor, not the pump rating.

Glenn Berger

8/22/2023 08:10:47 am

Based on what have described a 750 gpm fire pump would be acceptable.

Eric R

8/22/2023 08:18:14 am

NFPA-20 allows a centrifugal fire pump to supply a system up to 150% of its rated flow, with the annex adding in that the recommended range is 90%-140% of rated flow.

I wouldn't personally select a pump at 140%, but don't have any issue at all selecting a pump that may need to operate at 110%-120% of rated flow.

The code reference for this in NFPA-20 is section 4.9 in the 2016 edition.

Jesse

8/22/2023 09:47:11 am

I'm presuming you're calculating 2 standpipes for a demand of 750-gpm. A 750-gpm pump should work just fine.

Alex

8/22/2023 11:58:37 am

Run a calc and see where you land on your curve. I would say a 750 GPM is fine from what you said.

Chris

8/22/2023 12:23:21 pm

Perhaps a dumb question, but do you need a pump? can you get away with a manual standpipe?

8/22/2023 09:16:17 pm

My thoughts are the question shouldn’t be whether
you need a 750 GOM or 1000 GPM as the pump
is not going to create GPM

The question is what is your required pressure at
750 GPM and whether you need a higher pressure rated pump or inot

Jorge link

8/23/2023 11:23:34 am

The amount of water required in standpipes is addressed in NFPA 14, Section 7.10. If your hyd. calculations require less than 750 gpm's, and you have 2 or less standpipes the 750 gpm should be fine.

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Provide a 750 or 1,000 GPM Pump for Standpipes?

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