13D water supply rate requirements
13D water supply rate requirements
(OP)
I'm an EE working on a planned multistory 3800ft^2 residence in Northern CA.
The house must have sprinklers running off a single combined domestic/fire pump. I'm trying to SWAG the needed capacity for pump & power planning purposes. We are 6-8 months away from a sprinkler designer.
The house will have >10Kgals of potable storage, with 20 feet of positive head.
NFPA 13D <http://rrd ocs.nfpa.o rg/rrserve r/browser? title=/NFP ASTD/13D10> talks about water supply in Chap. 6.
Specifically, 6.1.3 states the quantity is at least 7 minutes times "the two sprinkler demand rate" unless the house is bigger than one story or 2kft^2.
I do not find a direct statement as to the required flow rate from the water system. I do find in 8.1.1.1.1 that the system must be able to provide 13pgm simultaneously to all sprinklers. (That's a LOT of water! With say 40 sprinklers... I must not be understanding it correctly....)
a) What does 8.1.1.1.1 mean?
b) Is there a direct statement re: required flow? If it is "two sprinklers" then a 1200 ft^2 house and a 4500 one would need the same pump.....
c) 6.1.3. addresses houses smaller than this one; what applies here?
d) The usual approach to meeting the varying pump demand is a variable frequency drive feeding the pump motor. (One brand name I find is "Aquaboost") But this house will be fed with 208/3ph. Has anyone found a VFD controller that accepts 3ph? [Yes, we could run it off of the 208, but that's a topic not 100% germane to this forum...]
e) The owner asked about external connections; so an outdoor pump could be used when the power is down. (CalFire requires a Emergency Power Off on the outside wall. But using it kills the fire pump...) Commercial building sprinklers have those for FD connections; has anyone seen such on a house?
The house must have sprinklers running off a single combined domestic/fire pump. I'm trying to SWAG the needed capacity for pump & power planning purposes. We are 6-8 months away from a sprinkler designer.
The house will have >10Kgals of potable storage, with 20 feet of positive head.
NFPA 13D <http://rrd
Specifically, 6.1.3 states the quantity is at least 7 minutes times "the two sprinkler demand rate" unless the house is bigger than one story or 2kft^2.
I do not find a direct statement as to the required flow rate from the water system. I do find in 8.1.1.1.1 that the system must be able to provide 13pgm simultaneously to all sprinklers. (That's a LOT of water! With say 40 sprinklers... I must not be understanding it correctly....)
a) What does 8.1.1.1.1 mean?
b) Is there a direct statement re: required flow? If it is "two sprinklers" then a 1200 ft^2 house and a 4500 one would need the same pump.....
c) 6.1.3. addresses houses smaller than this one; what applies here?
d) The usual approach to meeting the varying pump demand is a variable frequency drive feeding the pump motor. (One brand name I find is "Aquaboost") But this house will be fed with 208/3ph. Has anyone found a VFD controller that accepts 3ph? [Yes, we could run it off of the 208, but that's a topic not 100% germane to this forum...]
e) The owner asked about external connections; so an outdoor pump could be used when the power is down. (CalFire requires a Emergency Power Off on the outside wall. But using it kills the fire pump...) Commercial building sprinklers have those for FD connections; has anyone seen such on a house?





RE: 13D water supply rate requirements
With regard to pressures, I would shoot for about 18 psi for the head, 20 psi in friction losses, 8 psi for the riser (assuming a backflow preventer) and then whatever elevation you have.
Again, this is just a WAG based on a lot of assumptions.
Travis Mack
MFP Design, LLC
www.mfpdesign.com
RE: 13D water supply rate requirements
OK, so that's 40GPM plus 5gpm (from 6.5.2).
The 450 gallons is not an issue; CalFire requires 10,000g and the owner is going well beyond that.
BTW, CalFire is not keen on using swimming pools for that reserve. [This house will have a large one.] Their reason is in rainy season, they may pop out of the ground when emptied. If you insist, there's a big seismic report required, and a deed covenant forbidding abandoning the pool.
RE: 13D water supply rate requirements
6.5.2 In common water supply connections serving more than
one dwelling unit, 5 gpm (19 L/min) shall be added to the sprinkler system demand to determine the size of common piping and the size of the total water supply requirements where no provision is made to prevent flow into the domestic water system upon operation of a sprinkler.
I am assuming you are only serving ONE dwelling unit. If so, the 5 gpm is not needed. It may be good practice, but is not req'd.
If your ceilings have slopes >8:12 as is not uncommon for log cabins, you will not find a residential sprinkler listed for that slope. I had one jurisdiction where the AHJ said that if residential heads aren't listed, you have to use a standard where you can use QR heads. We had to do the system in the house per NFPA 13 because that was the only way we could get to use QR heads. 13R would not work because we had more than 4 heads in the dwelling unit, and 13R limits you to no more than 4 QR heads in the dwelling unit. It was a pain, but that is what we had to do.
Travis Mack
MFP Design, LLC
www.mfpdesign.com
RE: 13D water supply rate requirements
I misread 6.5.2; I thought it was about any combo systems.
That's not encouraging re: the slope; I'll mention it to the owner.
Still looking for the best VFD.
RE: 13D water supply rate requirements
RE: 13D water supply rate requirements
So the "10 minute rule" is moot in face of the CalFire requirement. My question is about the pump size, and thus power needs. I could not find the cite for "two sprinklers" in 13D.
I do have other questions but I'll put them in other threads.
RE: 13D water supply rate requirements
8.1.2* Number of Design Sprinklers. The number of design sprinklers under flat, smooth, horizontal ceilings shall include all sprinklers within a compartment, up to a maximum of two sprinklers, that require the greatest hydraulic demand.
Pump size is going to be determined by the piping configurations and elevations. One can typically do a residential fire sprinkler system for 60 psi.
Travis Mack
MFP Design, LLC
www.mfpdesign.com