I'd guess in the 350 to 400 gpm range if your main drain was attached
directly to the riser off a tee then 2" angle valve then drop to floor.
This is about 70 equivalent ft in length.    With 100 psi at the riser you'd
see a loss of 85 psi between the riser and the main drain outlet leaving
around 15 psi at the outlet of the 2" pipe.  Since a 2" pipe has
approximately 17 times the area of a 1/2" sprinkler I'd multiply 22 gpm
times 17 to get 374 gpm.

Purely seat of the pants but old seat in pants.

Bill Brooks

William N. Brooks, P.E.
Brooks Fire Protection Engineering Inc.
372 Wilett Drive
Severna Park, MD 21146-1904
410-544-3620
410-544-3032 FAX
412-400-6528 Cell

-----Original Message-----
From: sprinklerforum-boun...@firesprinkler.org
[mailto:sprinklerforum-boun...@firesprinkler.org] On Behalf Of
craig.pr...@ch2m.com
Sent: Tuesday, August 02, 2011 3:02 PM
To: sprinklerforum@firesprinkler.org
Subject: How much discharge from a 2" system drain

Plumbing engineer is asking how much flow could come from a 2" main drain at
the riser.  They are sizing floor sinks to capture the discharge.  No we're
not discharging it outside like usual.  This isn't a "usual" client.

System pressures from the pump are around 200psi static and 180 psi
residual.  That's a whole other issue.

Craig L. Prahl, CET   
Fire Protection 
CH2MHILL
Lockwood Greene
1500 International Drive
Spartanburg, SCĀ  29304-0491
Direct - 864.599.4102
Fax - 864.599.8439
CH2MHILL Extension  74102
craig.pr...@ch2m.com

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