Bad Smell From Bathroom, But Only At Night

19 Jun 2007
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United Kingdom
Hope someone can help with this?

We have a Georgian house, where at night, from the upstairs bathroom, there is the most terrible smell emanating from the room in general.

Essentially, it is not coming from a drain, rather from the room in general. The smell does not occur duing the day and there is no obvious blockage in the toilet, sink, bath or shower.

Also, the smell is travelling under the floor boards into the bedroom next door to the bathroom.

Why is the smell only happening at night, not even in the morning and what could the solution be?
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Are you on mains drainage or do you have septic tank ?
A dead rat or mouse gives off an evil smell :eek:
We are on mains drainage. The smell is definately sulphur dioxide (sewage) and it only ever appears when flushing the toilet or using the sink at night.
Do you have an AAV on your soil pipe which could be stuck and allowing loss of trap seal and letting smells in.

Would check the soil pipe first, is there a birds nest at the top blocking air intake :?:
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Erm, not sure what a syphonic pan is sorry! :confused:

If I change the AAV/Dervovalve, might that solve the problem?

Should the AAV/Dervovalve be outside or can it be inside as it is now?

How much access to ventilation does the AAV/Dervovalve need?

Really appreciate your help guys!

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