Odour from an internal drain cover

[JimmySaville]

I have just had an extension built at my house. The extension has meant that the drain cover is now inside the house and a double sealed cover was installed. However there is a very strong smell of sewage in the house. Not always but from time to time. The drain is at the end of the run so I wonder whether that is exacerbating the problem. I have also had Dyno rod take a look and there are no blockages. The smell seems to be coming out of one side of the cover. However I have had the drain cover looked at and the plumber thinks its fine although he now plans to come back and add a foam sealant to help. It's getting pretty desperate as the smell is sickening (not what you want in the kitchen when cooking/eating). Any thoughts?

[gas man]

either stop putting cigar ends down there,come to think of it i thought you were dead? or post some pictures up of the set up you have there see whats been done,the drain cover and under the sink

[aqualogic7]

dont use foam to seal cover as you wont be able lift cover if needed use grease as this seals and lid can be removed also check any other drainage connections are ok

[vectra65]

nothing worse than a internal m/h you say its the m/h at the end off the run is there any connections into the m/h really it should have been moved out off the extension before build no matter how much you seal it it will vent some fowl gases out if you carnt move it or fill it i would extend from back off m/h to a new vent pipe outside and pop a a/a/ valve on

[midge]

Is a manhole even allowed inside a building? (I'm gas qualified rather then water).

Maybe its not the cover but the haunching or pipe seals not made completely. If there's a smell then there must be an air-leak somewhere.

[Mike Jackson]

You can use a manhole internally as long as it double sealed. These have two sets of flanges and are screwed down. The gap between the two sets of flanges should be filled with inspection chamber grease which should seal against odours.