Hi-
in my toilet downstairs, I have a soil pipe in the corner of the room rising to about 6' high where it is capped with an air admittance valve. I've just had dado rail fitted in the toilet, and am wondering whether I can reduce the height of the AAV to (just) below the dado rail and then have it boxed in (with a brass grill for ventilation).
Further details:
The toilet also has a sink, and the exit drain is joined by a 2nd sink and washing machine outpipe in the next room before leaving the house where it goes straight into the ground. (I have a 2nd soil pipe which is vented from my upstairs bathroom running down the side of the house about 10' away).
From the research I've done, the AAV "must finish above the highest flood level of the space the valve is in...I.E. If the valve is in the same room as a wash hand basin, it must be higher than the overflow of that basin. This is so the pressure equalisation can occur without breaking the water in the traps."
I'm not quite sure what the overflow means - both sinks (the one in the toilet and the one in the next room) have S bends in their drain - is that the level of the overflow? or does it mean the overflow hole in the back of the sinks?
The height I'd like to replace the AAV would be only 3 inches or so above the S bend water level.
Thanks for any advice