"Frank Erskine" wrote in message
...

When I considered fitting an AAV a while ago I contacted the BCO and
was told that since I share a sewage manhole with my next-door
neighbour who still has a normal "stench pipe", this is acceptable,
that is, our communal m/h is adequately vented.

Yes, provided one of these is evident at least every few properties; for
buildings in between an AAV alone is OK. When I had this job done some
months ago, I had the AAV terminating within boxing behind the bath, but the
BCO insisted the pipe was extended upwards into the roofspace, terminating
there instead. I think this was a somewhat subjective opinion TBH; it would
be worth the OP discussing it with his BCO to see what's considered
acceptable; if it's the same as mine there wouldn't be a lot of point in
doing the work!

David