Soil pipe layout for ground floor flat

8 Sep 2014
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United Kingdom
I've had my arm twisted into finally doing the bathroom in our ground floor flat.

We want to change the current layout and we’ve figured out where we’d like things to go and having had a look under the floor the pipe runs look feasible after adding a drain connector and branch/boss to the existing clay pipe.

Currently the W.C. is the only thing connected to the existing clay soil pipe and the bath and basin waste goes to a separate gully drain.

I’ve drawn up my proposed soil/waste layout and wondered if anyone could provide any advice. I’d prefer not to have it but I wondered if I should have or the regs dictate that I should have an AAV at the WC end? Alternatively, would I be better keeping the soil and bath/basin waste separate? Both are possible, just thought it would be simpler and neater if all went in the soil pipe.


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Either option should be ok, critically though, can you get the correct fall on the WC pipework? Needs to be a around 1:40 or you'll have problems.
Thanks Hugh. I can get the required fall just didn't know if I needed to vent at the WC end or not but sounds like I don't have to.
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The builder who did my ground floor ensuite last year fitted a back inlet bottle gulley...


Then a floor boss adaptor inside that the sanitary appliances connect too. So if the trap seals are lost sewer odours won't enter the property.
Said it was required by BC.
Last edited:
It is permitted to connect directly to the drain provided the trap fitted to the appliance has the correct depth of seal.

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