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 _______________________________________________ Sprinklerforum mailing list [email protected] http://fireball.firesprinkler.org/mailman/listinfo/sprinklerforum _______________________________________________ Sprinklerforum mailing list [email protected] http://fireball.firesprinkler.org/mailman/listinfo/sprinklerforum -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://fireball.firesprinkler.org/mailman/private/sprinklerforum/attachments/20110824/0eebc788/attachment.html> _______________________________________________ Sprinklerforum mailing list [email protected] http://fireball.firesprinkler.org/mailman/listinfo/sprinklerforum _______________________________________________ Sprinklerforum mailing list [email protected] http://fireball.firesprinkler.org/mailman/listinfo/sprinklerforum _______________________________________________ Sprinklerforum mailing list [email protected] http://fireball.firesprinkler.org/mailman/listinfo/sprinklerforum
