We had a conservatory added to ur house. As part of its construction the soil stakc was capped with an Air Admittance valve. All has been fine for about 2 years.
About a week ago we noticed that the toilet bowl that drains into the stack that has the AAV at the top was filling and then draining slowly. Removing the AAV solved the 'problem', so I assume that soemthing has gone awry with the system.
Searching Google shows that the AAV has only a valve that is lifted by negative pressure in the soil stack. The valve seems in order when I remove the top cap. The valve slides up and down easily so I can't see what is wrong.
There are mysterious google references to AAVs being early indicators of drainage problems but I am not sure what kind of problem they indicate.
Any ideas?