DIY Doctor

Downstairs Toilet Bubbling When Upstairs Shower is used

Postby darthmuppet » Wed Dec 16, 2020 11:28 pm

I have a downstairs toilet that bubbles when the upstairs shower is in use. my house has 3 stacks - one for the main bathroom, one for the downstairs toilet and kitchen, and one for the en-suite bathroom (where the shower is). I have 3 separate rodding points and three ports open in the main drain outside. I am certain that they are as I describe as I saw the house regularly whilst it was being built, and I was actually there whilst the builder was leak testing. The downstairs durgo valve might be faulty, as it occasionally makes slurping sounds after a flush. That should not be relevant as it lets air in, not out. Downstairs loo is liquids only.

I think the bubbling is due to positive pressure in that drain. The house is a new build and all of the covers outside appear to be airtight / sealed. I am not a plumber or a civil engineer, but the symptom seems to suggest that there is a blockage in the street drain that is causing the pressure to build up in the sewer system somewhere, and back in to that drain. Two other people on my 80-house development have also reported the same symptom.

Aside from my suggestion, is there anything else that might cause this? is there anything I should check before reporting this back to the builder? I already plan to remove all the covers tomorrow and see if anything looks odd, but i'm not sure i'm going to find anything.


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