soil stack

[redsteels]

Hi all, first time on this forum for me as just recommended by a friend. I am in the process of refitting a bathroom in our house, at first floor level. We are using a new layout in order to give us a more usable space. The room is rectangular in shape and the old bath was fitted length wise in the room. The new layout is with the new shower/bath running across the room (full width 1700mm). My problem is the soil stack in the corner including the boxing around it means that I will have to bring the bath out from the back wall by around 8''. I am happy to do this but I then have to build a shelf, at a slight angle for the water to run off and into the bath. My question to you is, can I remove the vertical soil stack in order to move the bath back against the wall, optimising the space, and avoiding a potential problem of water damage a a later date if moisture get behind the tiled area. Where to soil pipe from the toilet joins into it, a run of only about 4 feet at just above floor level, will be hidden, and I would just fit a blank to cap off the pipe. It could be possible to fit a smaller diameter pipe of say 40mm to the soil stack at low level, take it out through the wall and vertically up the outside of the building about 18''and capped with an air admittance valve, but would that be sufficient? The waste runs from the manhole at the side of our house, about 20 feet before joining the sewer in our back garden. There is I believe two houses feed into it before reaching us and several after us before I guess it joins the road. Also joining the main pipe in the garden is the soil from our en suite which we built a couple of years ago. This has a soil stack on the outside of the building and is vented. Didn't mean to go on so long, just trying to give as much information as possible to get the most accurate answer. Many thanks angelo.

 

[JoeMar]

if there's another vented soil stack then there's no problem in getting rid of one.

 

[redsteels]

Thanks, that is kind of the answer I was hoping for. I wonder if there is anyone else out there who'd like to throw in their tuppence worth.

 

[Hugh Jaleak]

You'll need an Air Admittance Valve (AAV) at the very least I would think, flushing the W.C. could cause the bath or basin traps to syphon otherwise. AAV needs to be above the spillover level of the highest appliance (basin in this case i'd imagine).

You may get around the problem by extending the soil pipe past the W.C., then upwards and fitting an AAV on the end, or could you go through the wall and provide a vent/AAV externally? It is acceptable to reduce to 82mm pipework for the dry section of the stack.

 

[redsteels]

To reduce the size of the pipe down to 82mm would be an improvement. I would gain about 4'' as the boxing will be reduced from 8'' down to 4'' if you get my drift. Perhaps the best compromise would be to go out through the wall and vertically up the outside of the building, with the an air admittance on the end. I guess that would be the most amount of work but would cover all bases, gives me the maximum amount of room in the bathroom, and assures me the waste is vented correctly and no risk of syphoning. Thanks all for your advice.