Some AHJ's require that we use a parallel line for the reduced water supply so the residual would be reduced the same as the static, in this case 25 psi. The flow remains the same. Depending on the pressure decrease the graph could actually indicate a negative residual pressure at flow so a percentage reduction makes more sense. If the static reduction is 33% then I would reduce the residual 33%.
Ron Fletcher Aero Automatic Phoenix, AZ -----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of Steve Mackinnon Sent: Thursday, February 23, 2012 6:58 AM To: [email protected] Subject: Historical lows on Water Flow tests I have a question about the "Historical low" noted on Water Flow Tests from Government agencies (i.e. County, Town, City Water companies). Recently I received a test with the results; Static - 75 psi Residual - 54 psi Flow - 671 gpm. At the top of the letter they through in, "Historically, the static pressure in this area has been as low as 50 psi." So a 25 psi drop in static pressure. My question is, how do you adjust the residual pressure and flow? Normally I would lower the residual the same pressure drop as the static. With the above example, I would have a residual of 29 psi with a flow of 671 gpm. Should the flow change too?? Has anyone else experienced a similar situation? Thank you in advance for any guidance. Steven Steven MacKinnon Senior Fire Protection Engineer Hartcorn Plumbing & Heating Inc. 850 South 2nd Street Ronkonkoma, NY 11779 631-580-2300 - Office 631-580-1090 - Fax [email protected] _______________________________________________ Sprinklerforum mailing list [email protected] http://fireball.firesprinkler.org/mailman/listinfo/sprinklerforum _______________________________________________ Sprinklerforum mailing list [email protected] http://fireball.firesprinkler.org/mailman/listinfo/sprinklerforum
