I need to replace a 92.5 deg bend on a waste pipe with a dual 92.5 deg bend (rcb104) but the joints are solvent and i dont have the room to get below the join to hacksaw it and replace. is there a way to dissolve the solvent so i can remove the old bend and replace with new, or if i break into the old bend and tear apart will it seperate from the other part or will it likely damage the other part?
Also, can the venting pipe be replaced part way through with a smaller pipe and then back into a larger pipe? The reason I ask is the existing soil pipe is where i wish to place a new bath so would like to get bath flush to wall but cant due to venting pipe. the venting pipe at this point does not carry any soiling waste.
Any help on these two matters would be appreciated.

jason bullough, October 2008

the building regs say that the non-wet part of the soil&vent should be no less than 75mm. (Part H 1.32)

Jimster, November 2008

don't think so,the solvent works by melting the plastic of the pipe and fitting together,removing one will definitely damage the other,as for the vent,if there is no waste at all going through that part of soil stack then a smaller diameter vent will be fine but try and keep diameter as large as you can(no less than 1 1/2" but better with 2").

steeveepee, November 2008