Andrew Gabriel wrote:
In article ,
"JoeJoe" writes:
The waste run in my new kitchen is very long, and hence the BCO insisted on
installing an AAV on the 40mm pipe. The plan is to fit it under the worktop
next to the kitchen sink.

My logic suggests that the AAV needs to be fitted above the highest possible
water level in the sink. IS this really the case? i.e. do I need to re-think
my plan?

That's what you're supposed to do when fitting an AAV to a soil pipe.
If you need to get access to the pipe for rodding by removing the AAV
then any water trapped in the sink will not flow out through the AAV
since it's at a lower level. Having it lower than the highest water
level doesn't stop it working but may be messy in case of a blockage.

You can always drain the sink by undoing the U-bend.

MBQ