Right. And also, the flow rate is a false metric. Say you open a 2" main and flow it at 75 PSI residual. You get ... a LOT of water per minute, but it's only for about 15-20 seconds in a main drain test. In Southern California we've been wrestling with environmental regulations for 6 or 7 years and we're not allowed to let sprinkler water run off to storm UNLESS the storm drain system is fitted with sand/oil interception or filters or there's bio-retention on the site or ... omigosh, it's a total pain. So this is a panacea fix - since we started specifying this arrangement, all the bad people have gone away and we've never heard back from anyone that there's been an issue with overflow or splashing or any other issues.
SML From: Sprinklerforum [mailto:[email protected]] On Behalf Of John Paulsen Sent: Thursday, April 26, 2018 2:11 PM To: [email protected] Subject: RE: main drain flows Tony: What Steve is trying to say in his normal straight to the point way, is that a 4" drain will normally handle the 250 to 300 GPM max flow you get from a 2" main drain test. That is if your water company isn't providing flows over 90 PSI residual. Anything over 320 gallons exceeds 32 ft per second velocity and it takes more pressure to exceed that. John Paulsen - SET Crown Fire System Design 6282 Seeds Rd. Grove City, OH 43123 P - 614-782-2438 F - 614-782-2374 C - 614-348-8206 From: Sprinklerforum [mailto:[email protected]] On Behalf Of Tony Cetani Sent: Thursday, April 26, 2018 5:03 PM To: [email protected] Subject: RE: main drain flows They are looking for the GPM flows out of our main drain during a main drain tests. Since a lot of water is going to be released during the test they want to make sure the sanitary sewer can handle all the water with the main drain fully open under city pressure. Tony From: Sprinklerforum <[email protected]<mailto:[email protected]>> On Behalf Of Steve Leyton Sent: Thursday, April 26, 2018 1:53 PM To: [email protected]<mailto:[email protected]> Subject: RE: main drain flows Tell them you want a hub drain with a self-priming 4" trap. It'll resolve both 1ΒΌ" and 2" main drain discharges. Steve From: Sprinklerforum [mailto:[email protected]] On Behalf Of Tony Cetani Sent: Thursday, April 26, 2018 1:51 PM To: [email protected]<mailto:[email protected]> Subject: main drain flows Long time reader, first time writer.....actually not that long I'm a fairly new designer. We have a jurisdiction where they require the main drain to drain to a sanitary sewer and the contractor is asking what the flows will be so they can size their SS line accordingly. The sprinkler system hasn't been designed yet and they said they need to know right now so they can finish their design and submit for permit. Is there a way to figure this out (or get a ball park) just based off city water flow numbers? Thank you Tony
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