Light Hazard - Pre K School
Light Hazard - Pre K School
(OP)
I have a sprinkler contractor designed a 2 inches main for entire building (approximately 120 sprinkler heads). It is no a loop system!
Is the sprinkler need to be sized per NFPA table 22.5.2.2.1?
It appears to me that at least 4" main need for entire building.
Thank you.
Is the sprinkler need to be sized per NFPA table 22.5.2.2.1?
It appears to me that at least 4" main need for entire building.
Thank you.





RE: Light Hazard - Pre K School
Read more in chapter 22 of NFPA 13 for more info.
RE: Light Hazard - Pre K School
spkreng, CET
RE: Light Hazard - Pre K School
Remote area - Light Haz.
Density - 0.10gpm/ft@ for 1500 (actual 1530 sqft)
Total head - 5
K-Factor - 8
System Flow Demand - 300 GPM
System Pressure demain - 90 Psi
Base of Riser - 92
Safety Margin - 30 Psi
RE: Light Hazard - Pre K School
Now, it is rare to have a system where you do not have any over discharge of the sprinklers. If you have 120 psi available, then it may make sense.
Has a competent reviewer been tasked with plan and calc review? If so, then it it possible. If not, you should really have the plans/calcs reviewed by a competent reviewer for accuracy and compliance with an applicable codes/standards/insurance/local requirements.
Travis Mack
MFP Design, LLC
www.mfpdesign.com
RE: Light Hazard - Pre K School
spkreng, CET
RE: Light Hazard - Pre K School
spkreng - Yes, there is a fire pump house draw water from the pond.
Thank you all for quick respond.
RE: Light Hazard - Pre K School
1 - K8 at 24 psi = 39.19 gpm
2 - Assuming heads are pendent and ex cov, 33 gpm is min flow for most 18x18 coverages. At 20x20, you would need 40 gpm.
3 - If you have a pump drawing from the pond, any pendents must be on return bends.
Travis Mack
MFP Design, LLC
www.mfpdesign.com
RE: Light Hazard - Pre K School
spkreng, CET
RE: Light Hazard - Pre K School
200 gpm flowing through 2" Dynaflow with an ID of 2.203 produces a friction loss of 0.164 psi/ft so with 150' of main and 50' equivalent fitting losses he'd be looking at 32.9 psi.
Using the Viking VK602 add 17 psi for end head pressure and it is probable a 2" main is all that is needed.
5 flowing heads @ 33 gpm = 165 gpm which means 35 gpm overage to get to the perfect 200 gpm. It's totally possible.
RE: Light Hazard - Pre K School
How many sprinkler heads in 1 1/4" pipe? The designer got 18 heads for 1 1/4" pipe.
Thank you
RE: Light Hazard - Pre K School
You seem to be thinking "pipe schedule" methodology. We typically size pipes by calculation methods. He is probably calculating 3 heads on 1 line and 2 heads on another for a total of 5 sprinklers in the design area. Or, it may be 5 heads on a single line calculated in a corridor.
There are many different options as how to properly size and calculate a fire sprinkler system per NFPA 13.
Travis Mack
MFP Design, LLC
www.mfpdesign.com
RE: Light Hazard - Pre K School
spkreng, CET