Hi there... this is my first post so please forgive me if this thread is in the wrong place.
Anyway, my problem is... My downstairs toilet is hooked up to a Saniflow unit which takes all the waste into the main sewage pipe. When I flush the downstairs loo I get a horrible sewage smell coming from the upstairs shower drain??
Can anyone tell me why this would be happening? It was fine for a few years and has only just started to happen so I don't think it's to do with the drain set up on the shower.
Thanks in advance for your suggestions.