DIY Doctor UK DIY Forums

Hi I'm redoing my bathroom and part of that involves moving the waste pipes into the floor void rather than being visible above the floor.

The WC and Basin unit will be next to each other and I want both wastes to drop down into the floor before turning and exiting through the external wall. Here they will connect into a cast iron downpipe using McAlpine Push-Fit Single Socket Drain Connector (https://www.screwfix.com/p/mcalpine-pus ... 10mm/4255v)

My concerns are the location of the join between the 32 and 110mm pipe and also the vertical drops

Any guidance appreciated!

Hi bullbates1,
Suggest you extend the 110mm pipe so you can drop the basin waste into the top of the pipe. Blank the end using a ring seal coupler then if you find flushing the toilet breaks the seal in the basin you can add a bend and AAV.
Also suggest you provide a rodding access point in the external bend.
Regards S

Thanks for the reply. With it being in the floor structure I'll have installed the underfloor heating, insulation boards, tiles etc before actually connecting the fixtures to the plumbing so I need to get it right the first time.

What do you mean use a bend and aav, isn't my original diagram a bend option?

Hi bullbates1,
Your original diagram showed the basin waste going straight into the end of the 110mm. If you do not want the option of fitting an AAV you could just plug the end of the 110 but I would still suggest the basin waste feeds into the top of the 110 pipe.
If flushing the loo breaks the basin waste water trap you could fit an AAV in the basin waste pipe.
Regards S