Main Drain Flows as a % of static PSI
Main Drain Flows as a % of static PSI
(OP)
When performing the main drain flow test, at what percentage of the static psi should a low residual start to raise red flags or is this being too simplistic? I realize you don't want to bottom out but you'll get different results with different supply and drain pipe arrangements given similar static pressures. I've poured over my 13 and 25 again today trying to find a reference I recall from somewhere about how the main drain residual flows should be within a specific range. If it's too low you might have a design problem. If it's too high you may have to up-size your main drain to get adequate flows. Thoughts on both calculated and scheduled systems would be helpful.
Regards
Dave
Regards
Dave





RE: Main Drain Flows as a % of static PSI
RE: Main Drain Flows as a % of static PSI
13.2.5* Main Drain Test. A main drain test shall be conducted annually at each water-based fire protection system riser to determine whether there has been a change in the condition of the water supply piping and control valves. (See also 13.3.3.4.)
13.2.5.1 Systems where the sole water supply is through a backflow preventer and/or pressure reducing valves, the main drain test of at least one system downstream of the device shall be conducted on a quarterly basis.
13.2.5.2 When there is a 10 percent reduction in full flow pressure when compared to the original acceptance test or previously performed tests, the cause of the reduction shall be identified and corrected if necessary.
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Fire Sprinklers Save Firefighters' Lives Too!
RE: Main Drain Flows as a % of static PSI
To evaluate a water supply requires three variables: Static P, Residual P and the flow (Q). I've had engineers tell me the static P is 90 PSI and so everything should be good. I generally yell at the phone after I hang up.
If I'm missing something or you guys have some really cool trick that Bournelli or Hazen-Williams missed please let me know.
RE: Main Drain Flows as a % of static PSI
RE: Main Drain Flows as a % of static PSI
http://www
The 1994 flow test was 73 static / 68 residual @ 839 gpm
the 2009 flow test was 44/28/731
Main Drain Test Results
1997 - 54/45
1998 - 47/42
1999 - 49/40
2000 - 55/40
2001 - 47/40
2002 - 52/42
2003 - 45/40
2004 - 45/40
2005 - 50/40
2006 - 55/40
2007 - 50/40
2008 - 55/40
We never found out if the sprinkler system had a hydraulic calculation placard posted. BUT if it did and let just say it said the demand was 65 psi @ 750 gpm.
Do you think the main drain test results from above indicate we may have a problem with the water supply?? How much water does a main drain test flow? Well it depends on a lot size of main drain piping, water pressure, size of water main, fire pump etc. etc. BUT based on some testing we have done with an ultra sonic flow meter and varying water supplies a main drain can flow between 150-400gpm.
So with the above demand posted, water flow tests and main drain test results would you investigate this as a potential problem??
Just another good reason for the contractor to post a data placard on teh riser!
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Fire Sprinklers Save Firefighters' Lives Too!
RE: Main Drain Flows as a % of static PSI
RE: Main Drain Flows as a % of static PSI
RE: Main Drain Flows as a % of static PSI
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