The soil pipe from my bathroom passes through the outside wall and into the roofspace above the adjacent single storey kitchen before dropping into the ground at the end of the kitchen (about 4.5m out). The existing vent riser comes off outside the bathroom and rises through the roof on the outside wall to above the soffit of the first floor. This roof is being replaced and I am considering doing away with the vent stack by the bathroom and fitting it where the pipe exits the kitchen roofspace and drops into the IC which would only need to be about 900mm above the connection. I'm looking for clarification on what height I need to consider for the outlet of the vent and whether it needs to be above the overflow point of the WC (about 450mm above FF level) or the overflow point of the basin (about 900mm above FF level) bearing in mind any blockage in the pipe with result in the WC overflowing first. Part H doesn't seem to say anything.
