The fire department requires a min pressure for their pumper trucks to
operate as designed.
The suction hose has pressure losses.
Olie Olson, P.E.
Fire Protection Design
406-860-3170 mobile
406-628-2314 office
-----Original Message-----
From: [email protected]
Sent: Wednesday, August 24, 2011 8:27 AM
To: [email protected]
Subject: RE: Minimum pressures in water supply; Why 20 psi?
If <20 psi would collapse water lines, how do they remain intact when empty?
Craig L. Prahl, CET
Fire Protection
CH2MHILL
Lockwood Greene
1500 International Drive
Spartanburg, SC 29304-0491
Direct - 864.599.4102
Fax - 864.599.8439
CH2MHILL Extension 74102
[email protected]
-----Original Message-----
From: [email protected]
[mailto:[email protected]] On Behalf Of Smith, Steven
D. (CSFD)
Sent: Wednesday, August 24, 2011 10:16 AM
To: [email protected]
Subject: RE: Minimum pressures in water supply; Why 20 psi?
During a sprinkler design class we were told by the instructor that the
20psi comes from the health department and anything less than 20psi in the
mains will require citizens to boil the water to remove containments in the
water. Previously I had always heard anything less than 20psi could
potentially collapse water lines.
Steve
-----Original Message-----
From: [email protected]
[mailto:[email protected]] On Behalf Of David de
Vries
Sent: Wednesday, August 24, 2011 8:11 AM
To: [email protected]
Subject: Minimum pressures in water supply; Why 20 psi?
Does anyone know where the 20 psi minimum for undergound piping originated?
I have seen it in some state water regs, but have never been satisfied that
it is a sound, scientifically-based number.
I have also seen fire dept SOP's set an alert on suction pressure at the
pumper to 5 psi. Depending on the hose lay, that might equate to 20 (or 10)
psi in the main.
Dave
David A. de Vries, P.E., CSP
Firetech Engineering Incorporated
--- On Wed, 8/24/11, Letterman, Todd <[email protected]> wrote:
From: Letterman, Todd <[email protected]>
Subject: RE: Minimum pressures in water supply
To: [email protected]
Date: Wednesday, August 24, 2011, 8:27 AM
I agree with all who have responded and I'm not sure if there is hydrant
at the entrance to this place or along the street that could rob your
suction pressure. If there is a hydrant coming into the property, then
they are most likely going to start there hose lay at that point, which
may rob all the theoretical values so far. You are not going to have
much suction pressure at a 100%. If a fire takes it to that demand but
there is really nothing stating that you cant go lower than 20 unless
the water authority or other entity states other wise. It was never
stated if it is going to be a Electric or Diesel Driver or have you
gotten that far yet?
Todd Letterman
Fire Prevention Engineer CFPS
Riverside County Fire Department "Fire never sleeps"
(951) 955-5273 FAX (951) 955-4886
[email protected]
-----Original Message-----
From: [email protected]
[mailto:[email protected]] On Behalf Of Todd
Williams
Sent: Wednesday, August 24, 2011 5:21 AM
To: [email protected]
Subject: Minimum pressures in water supply
I am working on a new school project, where the building is 65 ft above
the water supply in the road and 760 ft horizontally. The water supply
is 54-46-1130. There is a pump planned, which I have to size. The total
pressure loss in the underground between the supply and the pump house
is approximately 30 psi. I know the general consensus (and some water
company requirements) is that the water pressure not be drawn down below
20 psi. A 500 gpm at 60 psi pump would be a good fit for this project,
but the suction pressures at the pump would end up being below 20 psi.
The supply in the public mains would remain above 20 (due to the
elevation), but would be below that in the private main at the pump
room. Any thought if this would be acceptable?
Todd G. Williams, PE
Fire Protection Design/Consulting
Stonington, CT
860.535.2080
www.fpdc.com
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