Help - what on earth is going on with my drains

[Flyingsouthwiththeswallows]

Sitting in the Living Room just now, I hear a deep rumbling from upstairs.

Investigating, I have a bath full of bubbles emenating from the bath plug hole.

Flushing the loo next to the bath, causes the water to rise in the loo pan, then release quickly sending more bubbles up through the bath plug.

Flushing the loo in the other bathroom, causes the same reaction. The loo fills to the top of the pan, then quickly releases sending bubbles up through the shower drain.

Back story. This is a newly nenovated property, but I have been fighting a smelly shower for some weeks. I have tried every cleaner imaginable to remove the smell but nothing works for longer than a few days.

I lifted the rodding eyes in the garden last week to check the drains were clear. They were pristine and water flowed clearly when I tried each of the taps.

The only other factor I can think of, is that we had a downpour of rain just before tonights problem.

Help. Could anyone advise what might be happening? Do I need a plumber or a drain specialist? Piglet John are you able to advise what might be happening?

"I do have a concealed cistern which is boxed in with the lid super glued down. Could it be in the boxing alongside the cistern? "

yes it could.

When you have your boxing smashed open with a big hammer, request that any future concealment is put together with visible chrome-domed screws so that it is easy to access. Including the bath panel. Lids don't even need to be screwed down. They can be hinged or lift off.

Thank you again Piglet John

This is turning into a nightmare.

There is no boxing in the bathroom corners, although I suspect that the whole back wall of the bathroom has a void behind it. Of course there is no access to that. Similarly there is no access under the shower tray without taking up a beautiful stone floor and no way of working out where the toilet waste runs and checking for the Durgo, without smashing the cistern casing.

I suspect Monday needs to be a renewed search for someone to do a camera survey for me and tell me what on earth is going on with the drainage in the house.

I am really shocked. The quality of renovation on this house is very high. My smelly shower drain is rapidly looking like it is going to turn into a very expensive issue and I just didn’t expect that here.

Even if the aav/durgo was stuck closed, if the underground drains are surcharging (ie full of water temporarily due to high rainfall) then you would still get a pressure of sewer gas in your house pipes and bubbling in whichever traps are shallowest.
So i don't think you should go destroying things on that account.
If you do want to prevent that you would have to vent your soul pipe properly at roof level which would cause some work but would resolve the issue if the drains filled up again.
Regarding the potentially faulty aav, that could cause the smell between the toilet being flushed and the shower next being used, try putting a glass of water down after flushing and see if that resolves it temporarily. Your bath might be acting as a soil pipe vent point which would not be nice if the wind is blowing the wrong way!

Thanks johnd2. Real food for thought there.

I am going back to the Builder tomorrow to ask where this AAV is, so that at least that can be checked.

Will then get advice this week as to how easy it will be to properly vent the Soil pipe.