Joe,

What is GPM (Q) at 20psi residual (R20) on your supply curve ?

John

-----Original Message-----
From: [EMAIL PROTECTED]
[mailto:[EMAIL PROTECTED] On Behalf Of Joe
Burtell
Sent: Thursday, July 31, 2008 10:20 AM
To: [email protected]
Subject: RE: Water Supply

The AHJ is what George said, not allowing me to extrapolate beyond the
test point on the curve of 1210 gpm. Does anyone know of any sections in
NFPA that would hint that I can extrapolate beyond the 1210 gpm or
can't?

-----Original Message-----
From: [EMAIL PROTECTED]
[mailto:[EMAIL PROTECTED] On Behalf Of George
Church
Sent: Thursday, July 31, 2008 6:12 AM
To: [email protected]
Subject: RE: Water Supply

I believe what Joe has encountered is an AHJ who doesn't realize what
EXTRAPOLATION on a water supply graph is.  Interpolating a point on a
curve is when the demand falls between your static and residual points;
extrapolation is when the demand is past the point where the residual
flow was measured. Chris is 100% right on the iffy-ness of a 300 GPM
flow extrapolated out to 1200. But 31 gpm past the measured point? I'd
ask the AHJ to cite code to indicate where you are wrong.

Probably time for a #13 committee member letter or an informal
interpretation. Or a day in hydraulics class for the AHJ?

glc

-----Original Message-----
From: [EMAIL PROTECTED]
[mailto:[EMAIL PROTECTED] On Behalf Of Chris
Cahill
Sent: Wednesday, July 30, 2008 2:19 PM
To: [email protected]
Subject: RE: Water Supply

It most certainly does in the context of lowering the residuals to a
pressure less than your design pressure and providing more water at a
lower pressure that is then boosted to the pressure needed.  This is
what we (or at least I) though Joe's problem was at first, he was 31 gpm
on the wrong side of the curve.

Perhaps it was the way it was implied that confusion was created. Agreed
pump's don't create water but create AVAILABLE water (to a point) at a
desired pressure.

Chris Cahill, P.E.
Fire Protection Engineer
Sentry Fire Protection, Inc.

763-658-4483
763-658-4921 fax

Email: [EMAIL PROTECTED]

Mail: P.O. Box 69
        Waverly, MN 55390

Location: 4439 Hwy 12 SW
              Waverly, MN 55390

-----Original Message-----
From: [EMAIL PROTECTED]
[mailto:[EMAIL PROTECTED] On Behalf Of
[EMAIL PROTECTED]
Sent: Wednesday, July 30, 2008 12:48 PM
To: [email protected]
Subject: RE: Water Supply

SNIP


And for others,  adding a pump does not create more water.   A pump will
not
add 31 gpm to the source.


Craig L. Prahl, CET
Fire Protection Group
Mechanical Department
CH2MHILL
Lockwood Greene
1500 International Drive
PO Box 491, Spartanburg, SC  29304-0491
Direct - 864.599.4102
Fax - 864.599.8439
[EMAIL PROTECTED]
http://www.ch2m.com


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