Does the loss of 30 psi include the friction and the elevation loss? If not, then you are getting pretty close to having cavitation at the pump inlet and/or collapsing the supply pipe.
Can you put the pump house lower on the hill? Matt Grisé PE*, LEED AP Sales Engineer Alliance Fire Protection 130 w 9th Ave. North Kansas City, MO 64116 *Licensed in KS & MO 913.888.0647 ph 913.888.0618 f 913.927.0222 cell www. AFPsprink.com -----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of Todd Williams Sent: Wednesday, August 24, 2011 7:21 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
