Rerouting soil pipe.

[Jimballs]

I'm hoping for a little bit of guidance

I have 2 bathrooms side by side

The left bathroom's toilet connects to the main soil stack and has its own vent (red)

the right bathroom has a soil pipe connected to the main stack (blue)

I want to move the toilet to the left hand side of the room - i have looked into routing it internally but the floor joists run parallel so the only option would be to box in the pipe and run it round two corners internally.

my other option is to remove the pre existing waste pipe (old bath drainage) (black) - drill a larger hole into the wall and connect it via a branch where the waste boss is and blank off the blue connection internally.

is this acceptable?

 

[Jimballs]

Image

 

[Hugh Jaleak]

Short answer is yes, go for the shortest route which sounds like the external connection where the bath waste joins, and reroute the bath waste to suit. Bear in mind routing internally to existing exit point may not allow for sufficient fall on the soil pipe either.

Altering the external pipework however allow for possibly a bit more work than you planned for! Existing soil pipe looks to have been there a few years, it may break when you attempt to cut it, so be prepared to replace sections if need be. Also looks like Terrain Solvent weld so will have to be cut carefully as joint wont be able to be dismantled.

Doesn't really need 2 vents, you could theoretically if desired, remove the Blue Connection and everything above it externally, and rejoin the basin waste in elsewhere. Depends if you're happy to keep the redundant connection internally and/or make good the wall.

 

[Jimballs]

Thanks for your reply, the pipework is indeed quite old, i assume 70s/80s going by the bathroom. I think I could achieve the fall internally but I really want to avoid boxing in if I can.
i may be best starting out with a completely new horizontal section and work from there.

basin waste on blue stack is redundant as bath will be moved to this side - thinking i could use a reducer into the old soil pipe.

 

[Hugh Jaleak]

Work your 4" runs out first and get the WC connected. Wastes are much easier to run to suit.