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Determining Standpipe Demand

Determining Standpipe Demand

(OP)
Hello All,
Recently, and rather abruptly, it came to my attention that I had some serious misconceptions about standpipes. In an effort to pin down some answers, I spent some serious time reading the books and reviewing information through various resources on-line. At that point, I reached out to two NICET 3's, one NICET 4,a P.E. with NICET 2, and a representative from the NFSA that teaches their layout classes, with my findings to see whether or not what I had put together was correct. Of these folks, only ONE (the gentleman from NFSA with 30+ years experience) agreed with what I thought to be correct. What I surmised from this, is that misconceptions about determining standpipe demand are very common, and that although one reputable person with a lot of experience agreed with me, that it's possible we are both wrong. In an effort to clarify for myself, as well as anybody else in the community, please peer review the information below for accuracy.

For class one and three standpipes...

-Fully sprinklered building, with floors less than 80k sq. ft. demand would be 500 gpm for the first standpipe, and 250 gpm for each additional standpipe, with a maximum of 1000 gpm regardless of the presence of additional standpipes.

-Fully sprinklered building, with floors greater than 80k sq. ft. demand would be 500 gpm for the first standpipe, and 500 for the second standpipe, with a maximum of 1000 gpm regardless of the presence of additional standpipes.

-Unsprinklered/partially sprinklered building, with floors less than 80k sq. ft. demand would be 500 gpm for the first, and 250 gpm for the second, third, and fourth, with a maximum of 1250 gpm regardless of the presence of additional standpipes.

-Unsprinklered/partially sprinklered building, with floors greater than 80k sq. ft. demand would be 500 gpm for the first, 500 gpm for the second, and 250 for the third with a maximum of 1250 gpm regardless of the presence of additional standpipes.

Thank you all very much for your time and consideration.

Best,

Jeremy

RE: Determining Standpipe Demand

Jeremy:

Yes, this is what I understand to be correct as well. However, you forget one caveat. That is horizontal standpipes. If you have a project requiring horizontal standpipes, you do 250 gpm at the remote and add 250 gpm at each additional to a max of 750 gpm for the horizontal standpipe.

The required pressure at the standpipe hose valve would be based on jurisdictional requirements. NFPA 14 puts it at 100 psi. However, some jurisdictions increase that to 125 psi or so, while others decrease it to 65 psi. It is always best to verify with the responding fire department as to what the pressures are to be.

Also, the location of the standpipe is driven by the jurisdiction. IBC says intermediate landing. NFPA 14 says main floor. Both say the AHJ is to be consulted as theirs is the final say in the location. Remember, the end user of the standpipe system is the responding fire department.

Travis Mack
MFP Design, LLC
www.mfpdesign.com
"Follow" us at https://www.facebook.com/pages/MFP-Design-LLC/9221...

RE: Determining Standpipe Demand

(OP)
Hi Travis,
Nice! Thank you very much for your input. I feel confident now that with three different people confirming this interpretation, it is correct. While on the subject of standpipes though, in NFPA 13 and 14 there are codes requiring that sprinkler demand be added to standpipe demand, or that sprinkler demand shall be used in lieu of standpipe demand when it exceeds standpipe demand. In these instances, would we be considering total standpipe demand? Say, if there were 3 class 1 standpipes in a sprinklered building with floors less than 80k square feet, the total standpipe demand would be 1000 (500, 250, and 250). So when determining whether or not sprinkler demand exceeds standpipe demand, would we be considering all standpipes in the building at that 1000 gpm number, or just one at that 500 gpm number because that is the single greatest standpipe demand of the three?

Thank you very much!

Best,

Jeremy

RE: Determining Standpipe Demand

In a sprinklered building, I do not believe there is any instance in the standard that requires you to ADD standpipe demand to sprinkler demand.

Your calculations are going to determine what is the most demanding. Think of this in terms of sizing a pump. For example, you could have an EH2 area that is calculated at 0.4/2500. This would be somewhere around 1100 gpm demand with typical overage. That demand would drive your pump flow rate. Now, let's assume that this fictitious building has 2 standpipes in it that are req'd to be automatic. Now, you have 750 gpm @ 100 psi demand. Let's assume you have 160 psi demand at 750 gpm at pump discharge. So, you would need a pump that has a flow rating of 1000 gpm and a pressure that would deliver 160 psi at pump discharge flange.

Hopefully this fictitious example clears things up a bit.

Travis Mack
MFP Design, LLC
www.mfpdesign.com
"Follow" us at https://www.facebook.com/pages/MFP-Design-LLC/9221...

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