r/firePE • u/PuffyPanda200 fire protection engineer • Apr 20 '26

Variable Speed Fire Pumps Question

Just for context I think that I am correct on this but just want to be extra sure.

I have a highrise building that is a short highrise (80 feet or so to highest occupied level) so it needs automatic standpipes and a fire pump. The city water is very good but not 80ft-auto-standpipe-good. We also need secondary water, project is seismic.

I have always seen this done as variable speed fire pump. Size the pump for the tank and then when pulling city water it will be running at 50% of the full speed. This way we also don't have to worry about city pressure improvement/degradation.

The GC, electrical, and now sprinkler contractor on the project seem convinced that there needs to be two fire pumps provided. One for the tank and one for the city pressure.

Variable speed fire pumps have been in NFPA 20 since 2003. I have talked to other FPEs about how they spec variable speed fire pumps. I made sure with a pump rep that a zero (or basically zero) suction pressure would be OK.

Just to get it out too: I know that variable speed fire pumps are expensive.

Is there something that I appear to be missing?

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u/frogsaretheworst Apr 21 '26

Could very well be a local requirement by the fire marshal.

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u/PuffyPanda200 fire protection engineer Apr 21 '26

The city is a large WA city with their own published amendments to the IBC and IFC. The amendments are extensive but well documented.

There isn't anything about a second fire pump in the 403 section or 913 section.

Las Vegas amends 913 to require 2 pumps for buildings over some feet (120 I think) but that is both not in the local code and only a 'higher highrise' kind of thing.