If the water purveyor objects (presumably based on potential collapse of your lead-in close to your pump room and backflow of ground water into the public supply), something to consider would be installing a double check BFP in a pit at the point of connection from the public supply. Then, even if there were damage to the lead-in, a highly unlikely event, no ground water would contaminate the public supply.
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/e04af788/attachment.html> _______________________________________________ Sprinklerforum mailing list [email protected] http://fireball.firesprinkler.org/mailman/listinfo/sprinklerforum
