I've had a problem for a couple weeks now whereby the toilet isn't quite flushing at the same rate as it once did. It still clears however air is coming back up through the bath drain (which is fitted with a small trap).
The bath drains normally with no air coming up through the toilet. An air admittance valve is fitted and if I remove this the problem mostly goes away indicating air is trapped as the waste goes down?
I've attached a picture so try and show the setup. The toilet connects to the right and the bath/sink go to the little one going to the left. The soil pipe is built into the cavity wall. There is an inspection cover outside but I haven't lifted it yet.
Where do I start?
//www.diynot.com/network/snoopy20/albums/12559/46846
The bath drains normally with no air coming up through the toilet. An air admittance valve is fitted and if I remove this the problem mostly goes away indicating air is trapped as the waste goes down?
I've attached a picture so try and show the setup. The toilet connects to the right and the bath/sink go to the little one going to the left. The soil pipe is built into the cavity wall. There is an inspection cover outside but I haven't lifted it yet.
Where do I start?
//www.diynot.com/network/snoopy20/albums/12559/46846
and the bath trap should be a deep seal one 
