Sewage pipe into 30mm basin pipe for basin drain

[slimsi]

Hi, have been searching through the forums but can't quite find the answer to the problem I have at our new house...

In our downstairs loo in an extension there is a toilet and a basin in a unit, nothing unusual.

Drain for the basin is normal 30mm with trap which appears to hold water ok and this then goes down the back of the unit into a rubber seal which is over a toilet.sewage sized drain.

The seal on the 30mm pipe into the larger pipe is ok but not tight you can put a finger in easily between the seal and smaller pipe.

There is a nasty sewage smell in the downstairs loo and I dont think its coming from the waste in the basin, my question is two fold:

1, is the rubber seal suitable for this use indoors?

2. is there a better option for indoor use that will seal in smells better than a rubber one?

Thanks

Simon

[lets have a look]

More than likely they used a 40mm rubber seal,change it to a 32mm seal or if it's hard to get at seal it with sealant/mastic,