What is the lowest demand pressure and flow you've come across for an ESFR system?
Looking big-picture at owner storage options early in a project (when we might have an idea on available pressure but don't yet have a plan to work from), the minimum flow and pressure we've come across as a minimum was 73 psi at 1,450 gpm. It was using (12) K25.2 sprinklers at 15 psi (minimum storage heights and a 250 gpm hose allowance). If we don't even have this supply, I typically anticipate a fire pump.
Have you seen any demands lower than this?
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12/18/2018 10:06:34 am
There are CMSA K25.2 options that could work depending on Hieght and class of storage. Refer VICTAULIC V4601 and V4603
12/18/2018 11:46:15 am
If you are preplanning for a fire pump, I definitely would not want to cut short my pressure when selecting a pump.
12/18/2018 12:28:50 pm
Agreed! Typically come across this situation just with pre-planning on whether the owner would need a fire pump or not.
12/18/2018 11:54:04 am
You don’t recall what the ceiling height was associated with this 73 psi system do you?
12/18/2018 12:28:06 pm
It was storage up to 20 feet, roof deck no greater than 30 feet.
3/16/2020 03:29:02 pm
This is exactly what i'm looking at now, though it is only for bid purposes and waterflow info is unknown. I was thinking of figuring for a fire pump to be on the safe side. Appreciate the info fellas
With larger pipe, you can get the demand down lower than that. I just looked back a project I did which required 1500 gpm at 65 psi, while flowing 12 x 25.2K heads at 25 psi each. We had to use 8/10" mains and 3" branchlines to do so, but the point is, it can be done if your structure can support the pipe sizes.
12/19/2018 10:10:33 am
Don't forget the 250 gpm hose stream allowance. I wouldn't price huge pipe sizes. It can become ridiculous. If the job calls for a pump, I would sell them a pump. If they are dead set against the idea of a pump and someone else wants to come in and undercut the job by designing very large overhead pipes- I don't want the work. The pump sets the client up for unlimited versatility in the future.
12/19/2018 12:42:00 pm
Yes, of course 250 outside hose was included (at the street, so not part of the 1500 gpm required in the bldg). I can understand your position, but In this case, I also sympathize with the Owners position; the added cost of pump is huge...need a pump room, which needs HVAC and electrical, plus a floor drain, and the cost that really goes understated is the added maintenance...with weekly runs, fuel, annual flow tests, etc. So the lifetime cost of a pump is significant. In my area (Hawaii), the construction alone for a pump + pump room is $250k-$300k, so a significant additional cost vs. utilizing larger pipe sizes.
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