Rented flat at the top of a converted house. Only recently moved in, usual story - flush the loo and the bath trap syphons... bad smell in bathroom etc. etc. Went into the attic, took the AAV off the soil stack and flushed the loo - problem solved. Also noticed when turning the AAV upside down that it takes a few seconds and maybe even a bit of a jiggle before the seal moves at all. So seems reasonable the AAV is knackered? But what I can't establish is... what happens if I don't replace the AAV and just leave the stack venting into the attic space? Im feeling conflicted. The poor landlord will get ripped off by the management agency if I complain about the syphoning drain and they send out a plumber to investigate and fit a new valve... but I equally know the agency won't take my word for it and just pay for a new dergo for me to fit.... but I'm also loathe to buy a new one for a property I'll only be living in another 11 months when I don't feel it's my job as a new tenant to sort rubbish like this out. so what happens if I just leave the soil stack venting into the attic... just a bad smell in the attic or am I going to accidentally blow the roof of or cause some sort of natural disaster?