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Sewage Smell Coming From Upstairs Shower Drain

Postby rosedani » Tue Jun 09, 2009 12:33 pm

Hi there... this is my first post so please forgive me if this thread is in the wrong place.

Anyway, my problem is... My downstairs toilet is hooked up to a Saniflow unit which takes all the waste into the main sewage pipe. When I flush the downstairs loo I get a horrible sewage smell coming from the upstairs shower drain??

Can anyone tell me why this would be happening? It was fine for a few years and has only just started to happen so I don't think it's to do with the drain set up on the shower.

Thanks in advance for your suggestions.
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Simply Build It

Postby plumbbob » Wed Jun 10, 2009 7:14 pm

Smells can only escape from any trap because the water seal is being broken. the problem here is why?

Pour a pint of water into the shower trap then in turn fill and empty the basin, bath (if you have one) and saniflow. Listen to the shower drain. Does any of them cause the drain to gurgle?
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Postby rosebery » Wed Jun 10, 2009 10:41 pm

"so I don't think it's to do with the drain set up on the shower."

I do. The water is being sucked out of the shower trap by syphonage. Get yourself a plumber in to look at the exact situation and recommend a solution.

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Postby blenkhorn » Fri Jul 03, 2009 12:26 pm

It is definitely to do with the drain set up.
Either, the water is being syphoned out of the trap by the vacuum created when the saniflo switches on, or you have a 'continental' style outlet from the shower which has no trap as such, or there is a blockage in the soil vent pipe.

I found a site which explains this if you
Google ""
and also explains how you can stop the problem.

I used the HepVo dry trap on my shower ( had to cut a hole in the downstairs ceiling to fit it - but it was worth it!) and it worked a treat! No more having to keep the en-suite door shut to stop the stink coming into the bedroom at night. My shower was the 'easy-plumb' continental type outlet drain.
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