WC Smells Drainage and wastage systems and plumbing help, advice and answers

[ronniebear]

We have two WC's one on the ground floor and one in the family bathroom on the first floor we get sewage smells in the ground floor wc and I can find no gaps round any of the waste pipes.
In the loft there is a one and a half inch pipe sticking up out of the soil stack and thats it .
it is all boxed in floor to ceiling
has any one any Idears :(

[Bob Plum]

Don't use the upstairs WC or bath for at least an entire day - if you get no smells in the downstairs loo, the waste from the upstairs is pushing gas through the downstairs loo. You could try flushing the upstairs loo while someone watches the downstairs to see if gas bubbles back.
If that is the cause of the smell, the actual cause is probably a partial blockage below/downstream of the downstairs loo somewhere.