Basin waste into bath waste

24 Nov 2020
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United Kingdom
Hi , I'm redoing our ensuite and I have had to strengthen all the joists with ply before even thinking about the plumbing side of things .
The old waste pipes were located through 60mm holes drilled through every joist the whole length of the room .I have fixed the joist and now want to run my waste pipes at surface level behind a stud wall I'm going to build as I don't want to ruin all the strengthening work I've done .
We will have 2 X 600 vanity sinks at one end of the room and I want to run the 32mm waste from these to the bath and then connect to 40 mm for all 3 to discharge into then out to the soil stack . I'm concerned that the bath may get basin water backing up to it or does the trap stop this ?
I'll be using a 40mm y connector at the bath .
Is this the right way to do it ?
Thanks in advance


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It'll work but better to take them out to the stack separately in my opinion.
I could probably get them pretty near the stack before I connected them .
Do you think that will make it any better ?
Thanks for replying
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Unlikely that the basin waste water will back up into the bath unless there is a blockage downstream. If that is the case, it'll give a safe indication of the problem that needs sorting out. Would be a problem if it was a shower rather than a bath as this could overflow much sooner.

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