Extending soil pipe for new upstairs bathroom

[thecommiser]

Hi All

We have recently bought a new house, and are really struggling to get a plumber to route a new soil pipe for us. Every one I have spoken to is always vocal about how busy they are, and then of the few I have gotten round to quote, have either never gotten back to me, or quoted high (£300 in parts alone). So I was looking to do the work myself, as BCO are going to be involved either way....

Long story short, I am after some guidance on routing the 110mm Soil Pipe, and getting the bends in the right place. I have taken a couple of pictures, and with the power of paint, drawn how I would look to route the pipe, but the 3 90degree's in short fashion (4 if I include the toilet I suppose), & the 110mm core drill worry me a bit...


The 2 pictures side by side show either side of the same wall. On the left there is an existing toilet at floor level, with a pan going straight down into underground pipe (no Vent or AAV on this side of the house that I am aware of at present).
I would plan to take the existing toilet out, having a branch at floor level, and have the toilet mounted further forwards than current (I would create a false wall). From here, move to the corner via 2 135 degree corners, and raise up to the ceiling level.
I think this is all ok, however this is where it gets tricky.... I figure I would need a 90 degree to come "forwards" away from the back wall, and then another 90 degree to go through the side wall (this is an old external wall, so double skin, and presumably a lintel above what used to be the window opening)
Once through the wall, (Lintel is marked in white, the upstairs front wall marked in yellow), I would need another 90 degree to carry on vertically, followed by a branch for the new toiliet and an AAV.

Short of going through the double skinned wall at an angle, is this the only/best way to route the pipe (the ceiling will be dropped to conceal on both sides, and as mentioned the back wall in the existing toilet will be boarded out to conceal, so "Neat" running is less important than good flow I think). Also which elbows should be "Accesible" Elbows, I know BCO will have their own view on this, but thinking from costing at present....

 

[Hugh Jaleak]

Bends in the wet section of a stack are usually frowned upon, but there are times when its unavoidable. I would firstly be looking to minimise the number required, so would suggest you come straight up from the current drain position, try and go through the wall in the corner, then turn 90° to come forward, before turning upwards to new WC position. May help avoid the lintel, I would worry about compromising that personally.

Alternatively, what's above? Have you checked direction of floor joists, any scope for running some of it in the floorspace above the ceiling or through the room above? Access elbows are a good idea, although pray you never need them....

The other issue may be the drain, regs state a rest or long radius bend is needed at the bottom of a stack, if the existing drain has a tight radius bend then connecting a stack may cause issues.

 

[thecommiser]

As I understand, your route would avoid the 2 135’s, at the sacrifice of the soil pipe running up the centre of the wall, but the 3/4 90s at the high level would stay the same...

I hadn’t thought about digging out the ground to put in a rest bend... doesn’t sound like fun