Just started work on a new en-suite & I’ve hit a problem with the proposed (& really only) internal stack location. On taking up the f/boards, I’ve discovered there are 2 joists straddling the supporting wall & it’s just my luck that the full span joist is the one in the way, if it was the other side I could have just cut off the offending overhang. This will kick the stack out another 50mm & the space available was always tight (but just doable) because of a door opening below (only 150mm from the adjacent wall). Loosing 50mm brings the stack out over the door line so it needs to be offset around the joist & back to the wall; this would be easy to achieve using 2 x 45 degree bends as it passes through the ceiling but then I checked part H & it states “no connection within 750mm of the offset”!
Is it really not permitted to connect adjacent to such a small (60mm) offset? Am I interpretation Part H correctly? If so, how the hell am I supposed to connect the toilet, shower & sink (only about 350mm above) into the soil stack! Are BC likely to waiver this in such a case or am I going to have to go to all the agro of moving the door below (major work) just to get a straight stack in. Could I consider an external stack? I didn't want this as it's at the front of the house so not ideal; am I likely to need PP for an external stack in this location? I know I will ultimately have to ring BC for a way forward but I would appreciate confirmation from the more experienced on here that I am in fact interpreting part H correctly; any info or advice would be much appreciated.
Is it really not permitted to connect adjacent to such a small (60mm) offset? Am I interpretation Part H correctly? If so, how the hell am I supposed to connect the toilet, shower & sink (only about 350mm above) into the soil stack! Are BC likely to waiver this in such a case or am I going to have to go to all the agro of moving the door below (major work) just to get a straight stack in. Could I consider an external stack? I didn't want this as it's at the front of the house so not ideal; am I likely to need PP for an external stack in this location? I know I will ultimately have to ring BC for a way forward but I would appreciate confirmation from the more experienced on here that I am in fact interpreting part H correctly; any info or advice would be much appreciated.
.....It`s to do with air being compressed as water hits and runs along the horisontal part of the stack ......and in this case it`s negligible........tell BC this and say you`ll use HepV O waste valves on shower and Basin. 
