Shower waste into horizontal soil pipe?

12 Dec 2006
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United Kingdom
I'm refurbing my downstairs toilet/shower room and connecting to an unvented stub stack. In the new layout the shower will sit between the toilet and the stack. Is it OK to connect the shower waste using a very short 40mm pipe run direct into the horizontal(ish)110mm waste that runs from the toilet using a strap boss. I would like to do this instead of using a boss on the stack as this would give me a *much* shorter and less convoluted pipe run for the shower waste, with no need to avoid joists etc. Based on past experience I am paranoid about shower/bath waste blockages, and once the shower tray and floor tiling is down it's not coming up again in my lifetime. Thanks in advance for any advice.
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That's almost exactly what I did with the help of my neighbour, who is a retired plumber. I have a wash basin and a home urinal both draining into the horizontal section downstream of the WC.
Thanks RR - I couldn't imagine any theoretical or practical reason not to do this, but nice to know someone who has and that it works :D .
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As long as you can get a small fall on the waste pipe you should be ok.

Might mean building up your shower tray to achieve this :D

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