I have a 110mm vent pipe running up the wall of my en-suit into the loft where an air admittance valve has been fitted.
Is it possible to reduce the vent pipe to 2 inch to create more space for a shower enclosure. I know you can get reducers and was planning to reduce the pipe just below floor level and then increase its size back to 110mm in the loft so the air admittance valve can still fit.
Any advice much appreciated!
