minimum water flow required for residential fire sprinkler

[dj654]

I have hydraulic calculations done for my fire sprinkler system, but I can't figure out what is the minimum water flow that should be provided to the whole system. Does NFPA 13D specify how to compute that? Can it be deduced from hydraulic calculations? The reason I am asking is because I am trying to figure out if I can reduce the water meter size at my home since utility charges much higher for 1.5" meter vs 1" meter.

 

[SprinklerDesigner2]

Best thing you can do is take the drawing and calculations to a licensed fire sprinkler contractor and ask them. It isn't a matter of re-calculating everything just the head loss through the meter and underground.

(Side note: If you have drawings and calculations never lose them. I would advise getting them copied to a pdf document and save them in multiple places).

That all said the flow will not change it's all about the friction loss through the underground and meter.

 

[stookeyfpe]

Option B: If this a one-family or two-family dwelling or a townhome regulated by the International Residential Code (IRC), you can use the pipe schedule method in IRC P2904. In this case the IRC (and NFPA 13D) have prescriptive design values for pressure loss through meters, pipe & fittings, and elevation. Be sure to follow SD2's guidance concerning the meter and supply piping.

 

[MatthewJWillis]

I don't have anything technical to add.

Just wanted to commend you for taking the steps for protection.

R/
Matt

 

[dbill74]

Your minimum water flow should be a part of the hydraulic calculations. It's rather hard to compute pressure drops in piping if you don't know the flow rate through the piping. And you need to know pressure drops to be able to select the proper sized piping.

 

[dj654]

dbill74, this is what I thought too. But the answers I am getting seem to indicate otherwise. I am attaching the hydraulic calculations, but I don't see minimum flow required anywhere.

I also talked to the fire marshall and a fire sprinkler guy and they all kept talking about running the calculations again. All I want is what is the flow requirement for my currently installed system. It almost sounds like fire sprinkler doesn't determine your minimum flow requirement for the water supply which is strange.

 

[TravisMack]

It looks like you have 18 gpm flowing through your meter based on that. It appears that there is a 16 psi or so margin in the calcs. If your smaller meter does not have more than that in the pressure drop then it may be permitted.

However, you need to pay a competent individual to evaluate this properly. You don't want to trust some one you don't have a business relationship with to answer this over an internet forum.

Travis Mack
MFP Design, LLC

http://www.mfpdesign.com

"Follow" us at

https://www.facebook.com/pages/MFP-Design-LLC/92218417692

 

[cdafd]

74
I will give you my non engineer answer

The reason they say recalc because the change in meter size will change the cal so
You can't just say well my present calcs say I need this flow and pressure so if I change meter size it should work. Needs to be recalced

 

[cdafd]

There are also approved self contained systems

Pump, tank and you are ready to go

http://www.spdinc.com/products/residential.html