You need to perform the full test in accordance with the standards. I have seen several cases where the backflow devices passed the backflow test but would not flow without excess pressure loss. Fine sand or silt had built up in the chambers. I was told by a backflow industry expert that the backflows are designed to be flowed often. When they sit with no flow or with small flows, the backflow tends to collect silt. This is what had happen on three of my projects. We measured the loss through the backflow and there was over three times the published value. The backflow was cleaned and retested. The results were what they were supposed to loose. Test the backflow and full system demand once a year and measure the flow and the loss. The standards do not care how you flow just that you flow and measure.
John John August Denhardt, P.E. Strickland Fire Protection Incorporated 5113 Berwyn Road College Park, Maryland 20740 Office Telephone Number: 301-474-1136 Mobile Telephone Number: 301-343-1457 FIRE SPRINKLERS SAVE LIVES -----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of Ron Greenman Sent: Tuesday, May 11, 2010 12:17 AM To: [email protected] Subject: Re: DCVA test connection First I haven't seen any definitive consensus as to what needs to be flowed: A flow sufficient to fully raise both checks off their seats or a flow sufficient to raise the checks enough to meet the calculated flow or a flow sufficient to substantially raise the checks. And if the first two how do I know I've done either? And where in 25 does it say I have to prove anything? I contend that the reason for this rule originates from the days when we first were required to install backflows on sprinklers the available models were weighted swing checks. At that time there either was a real or perceived fear that these types of check valves might not operate properly after long periods of inactivity. I would also suggest that main drain flows should be sufficient to demonstrate an operational valve set. This begs the question then that why would the committee require a separate test and the answer might be that the requirement is added separately to define the need to separately record each part of the test, i.e.: the water supply as measured through the main drain displays properties consistent with, or inconsistent with the last test, and that the backflow appears to be operating properly or not. There is no place in 25 where anything else is required to be calculated and without measuring instruments and calculations it is impossible to determine a given flow. On Mon, May 10, 2010 at 7:57 PM, [email protected] <[email protected]> wrote: > In many cases one hose is enough for the flow needed > > Forest Wilson > Cherokee Fire > > Sent from my Verizon Wireless Phone > > ----- Reply message ----- > From: "tom poisal" <[email protected]> > Date: Mon, May 10, 2010 8:01 PM > Subject: DCVA test connection > To: <[email protected]> > > Just a question, what happens after you have reversed the check valve > or removed the clapper; when the water hits the clapper (or dual > clappers) in the F.D.C. as you'll still only get a flow from one 2 1/2 > outlet on the former and the latter - stoppage ? so then just remove > the clappers? > > -- > Tom Poisal, CET > _______________________________________________ > Sprinklerforum mailing list > [email protected] > http://fireball.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 > [email protected] > http://fireball.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) > -- Ron Greenman Instructor Fire Protection Engineering Bates Technical College Tacoma, WA Member: AFT WA 4184/AFL-CIO, SFPE, ASCET, NFPA, AFSA, NFSA AFAA, NIBS, WSAFM, WFC _______________________________________________ Sprinklerforum mailing list [email protected] http://fireball.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 [email protected] http://fireball.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)
