Foul smell in ensuite shower room

[Red Eye]

Hello
We have a very bad sewerage smell coming from a newly installed ensuite - shower, sink and toilet. There is an AAV in the system which has been boxed in and tiled. The shower is a low profile drain design and the trap is full of water. There are 4 other bathrooms in the house (with roof vents) that do not smell. The smell is bad and we can't use the room. Any ideas would be welcomed? Thanks.

 

[Ian H]

Smoke bomb from the nearest manhole. Replace the manhole lid ASAP and run inside for a look/sniff.

 

[Red Eye]

Thanks. Where do you buy smoke bombs from?

 

[Ian H]

I get mine from Travis Perkins but all builders merchants should do them. Avoid the matches, get the pellets.