George, I thought that if you did not flow past your gauge hydrant that your residual reading would be off. Have I been wrong all these years?
-----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of George Church Sent: Friday, January 23, 2009 11:47 AM To: [email protected] Subject: RE: water test location Maybe I have Friday-it is, but what possible difference could it be to reading pressure at a point whether your gauge is attached to a hydrant, city side of a BFP as Todd did, or a hose bib on a house with another faucet cracked open to prevent their BFP from being closed? Its accurate measurement of the pressure that is important, not the method of attachment to the piping network. I just did a flow test on 12/26 for a grocery store. My competitors had run a test for the same property for their adjacent strip stores. They flowed the hydrant at the site, and took static and residual at a hydrant 44' below the site, 1/4 mile away, because there was only one hydrant in the shopping center, out front of an existing store. I flowed the hydrant out front, and took pressure readings from the same place Todd did, city side tap on BFP. Sure, the readings were past the point I was flowing. But you can't tell me that it is more accurate to ignore 1/4 mi of piping, along with large elevation differences, versus data collected right at the site with a minimum of corrections required. We adjusted for lowest tank gradient, I cannot tell from their results if they did or not. But somehow, they end up with 10 PSI more pressure than I did while flowing twice the volume. So its not a surprise they beat my bid on their strip stores, eh? Of course, my COR for a fire pump should make up for that, and I wonder what the local AHJ will say about the divergence of supply when looking at the two submittals at same site? That's one where I wouldn't want to be hanging pipe in advance of approvals :) since I hope the AHJ investigates further. Another time when calibrated gauges and hose monsters and adjusting for tank gradient versus "saving money" and using a pitot tube will pay off when explaining test procedures if asked by the AHJ so he can ascertain who has the more accurate depiction of the real supply at the site? glc -----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of Jim Johnston Sent: Friday, January 23, 2009 11:05 AM To: [email protected] Subject: RE: water test location Todd, I have never heard of testing this way, I have always used a minimum of two hydrants. On a looped system if you have the manpower or water usage isn't an issue use three hydrants taking the pressure readings from the middle hydrant. Do you have access to NFPA 291, this has some good diagrams for you to use. Jim Johnston, P.E. Fire Protection Engineer Inland Fire Protection, Inc 1100 Ahtanum Road Yakima, WA 98903 Phone 509-248-4471 Fax 509-248-1180 [email protected] -----Original Message----- From: Todd Williams [mailto:[email protected]] Sent: Friday, January 23, 2009 7:30 AM To: [email protected] Subject: water test location I did a flow test a couple of days ago on an underground main that had recently been looped. There is a main that feeds a hydrant and sprinklers to the building at the end of the loop. I flowed the hydrant and read the pressures off the first test port on the backflow preventer (before any checks) on the system riser. The contractor called me this morning and said my test was not valid because I didn't use two hydrants, like it says in NFPA. I think I am OK and the effective point would be the connection of the main to the sprinkler system feed. Am I right or am I missing yet another obscure ruling? Todd G. Williams, PE Fire Protection Design/Consulting Stonington, Connecticut www.fpdc.com 860.535.2080 _______________________________________________ Sprinklerforum mailing list http://lists.firesprinkler.org/mailman/listinfo/sprinklerforum For Technical Assistance, send an email to: [email protected] To Unsubscribe, send an email to:[email protected] (Put the word unsubscribe in the subject field) _______________________________________________ Sprinklerforum mailing list http://lists.firesprinkler.org/mailman/listinfo/sprinklerforum For Technical Assistance, send an email to: [email protected] To Unsubscribe, send an email to:[email protected] (Put the word unsubscribe in the subject field)
