# Pool backwash to sewer



## mass plumber (Oct 25, 2017)

Hi, Guys
I have an issue that i have never ran into before, as so the 2 local inspectors. 

I have a customer with a hotel. The hotel has a under ground pool that the, pool back wash goes up to the 1st floor building drain tied in directly.

So how to separate this by means of an "air-gap".

My only thought is to size an ejector pump, holding tank, trap vent, vent through roof, run pump drain to building sewer. The inspector agrees that this would work. But its crazy $$...just for a pool backwash. 

Is there anything else to do? Thought of an rpz, but thoughts are the pressure from the backwashing would screw it up.

Oh, and there isn't any place to put a dry well or exterior tank.

Thank you


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## Tango (Jan 13, 2018)

What size is the drain pipe? What I usually see but not for pools is a drain pipe discharging in a funnel to a floor drain. Sometime you have 6-7 different drains in it.


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## mass plumber (Oct 25, 2017)

Hi, Tango
Yes your correct, 
my issue is the building drain is 6inch witch is fine, but its underground, and @ ground level. So its tough to describe, picture a pool and level of rooms above pool, then ground level then more rooms above. Making this a chore already vtr/ drain to sewer.

Wondering if theres a double check of some sorts, which would be easy to install. But none to my knowledge are rated for a pool backwash.


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## ShtRnsdownhill (Jan 13, 2016)

why cant you just put a receptacle on first floor drain and have pool discharge pipe above the rim of that receptacle ? that would be an air break...


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## exclamation (Mar 11, 2013)

I wouldn’t think it would be any different than any other pool backwash unless it needed to be tied in outside above ground and the pump wasn’t strong enough to lift that much- I’m no pool expert at all tho.


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## GAN (Jul 10, 2012)

Yep no direct connection even though the pool water is no longer potable you don't want to risk a sewer back up into the pool. So a floor type sink with a fixed air gap from the pool backwash.

The pump should be able to handle 10' of head pressure so it would be just a matter of a hub drain or floor sink to provide the drain. At least 4" with a 16" to 24" floor sink. If you just attempt to have a fixed air gap directly form the pump discharge into a hub or FD, your asking for splashing problems.


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## Toli (Nov 7, 2015)

You might want to find out the gpm of the pool pump and then find out if it’s doing the same gpm during a backwash. I have a couple pools that I help maintain. One has a 4” Aurora pump @380 gpm. I would suspect a hotel pool wouldn’t be that high.

I'd hate to see you size something too small. Is there a storm sewer somewhere you could go with it? Would that be allowed where you are at?


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## mass plumber (Oct 25, 2017)

Thanks, So my idea of the pump/ holding tank/ sized correctly/ stand pipe is the only thing to do.

Yes do need to size correctly, as the pool is 40x70x12ft deep, and a backwash cycle lowers the water 2inches...


A receptor/ floor sink/ vent would work. But looking at operations, the lift of the pool pump and when the pump turns off, you can tell/ feel like the pool pump barely has enough lift/ head psi.


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