Fire pump flow
Fire pump flow
(OP)
Good day,
I am checking the fire drawings of a project, The fire pump is sized to be 1500 gpm, but as per NFPA 14 section 7.10.1.1.5 "The maximum flow rate shall be 1000 gpm (3785 L/min) for buildings that are sprinklered throughout, in accordance with NFPA13, Standard for the Installation of Sprinkler Systems, and 1250 gpm (4731 L/min) for buildings that are not sprinklered throughout, in accordance with NFPA 13." my project is fully sprinklered so I proposed to change the pump to 1000 gpm. But he designer claims that additional 500 gpm is needed for external fire hydrants.
My question is there anything in NFPA that say I need to consider for internal and external fire at the same time and if possible to point which sections talk about this issue?
I am checking the fire drawings of a project, The fire pump is sized to be 1500 gpm, but as per NFPA 14 section 7.10.1.1.5 "The maximum flow rate shall be 1000 gpm (3785 L/min) for buildings that are sprinklered throughout, in accordance with NFPA13, Standard for the Installation of Sprinkler Systems, and 1250 gpm (4731 L/min) for buildings that are not sprinklered throughout, in accordance with NFPA 13." my project is fully sprinklered so I proposed to change the pump to 1000 gpm. But he designer claims that additional 500 gpm is needed for external fire hydrants.
My question is there anything in NFPA that say I need to consider for internal and external fire at the same time and if possible to point which sections talk about this issue?





RE: Fire pump flow
RE: Fire pump flow
and still not clear if it is sprinklered or not
RE: Fire pump flow
To my knowledge, you do not add outside hose allowances to an NFPA 14 standpipe calculation. Maybe he is supplying outside hydrants from the pump and needs the 1500 gpm to meet the site fire flow requirements. For example, if the site fire flow requirements from IBC are 2000 gpm, then the 1000 gpm pump would not cut it, but a 1500 gpm would.
So, as stated above, more information is needed to determine the pump options.
Travis Mack
MFP Design, LLC
www.mfpdesign.com
RE: Fire pump flow
RE: Fire pump flow
Is it a good argument to rise that at 150% of rated capacity, the pump will provide the 1500 gpm, while maintaining 65% of rated head? The pump head is calculated assuming 100 PSI at the most demanding landing valve, at 65% of rated head the pressure at landing valve will drop to about 65PSI which is still in range as per NFPA 14. But if this is applicable do I need to size the pipes and pump head at 1000 gpm or 1500 gpm.
Thanks for your help.
RE: Fire pump flow
Following NFPA 20, work with the pump curves maybe not to 150% capacity but for a little less like 140% for flow and some psi of pressure as safety margins, to see if the pump suits.
About the pipe diameters, follow hydrualic calcs. do a good hyd. calc. for design scenarios or ask an expert for this.
RE: Fire pump flow
Another comment was right on the mark about terminology. Before I hired him away from public service, my company's design professional was a PRO (plan review officer), he always said "The building and fire codes tell you what has to be sprinklered, the standards tell you how to do it."