Replacing solvent welded waste pipe

[boyse7en]

I need to replace a piece of damaged waste pipe. It's about 2m long and is solvent welded into a 90deg elbow at each end.

It's been in situ about 30 years so I doubt that I'll ever be able to "unweld" the elbows to remove it, so my plan was to cut out the damaged bit and replace it, with a straight coupler at each end to join it to the old pipe.

But then I realised that I won't be able to fit the new pipe in, as it will be exactly 1/2 a coupler too long until it is in position to slide over the old pipe.
How do I get around the problem? Can "split the difference" and have the pipe going only halfway into the coupler at each end, or will that not seal?

[wolfracesonic]

At 2 metres long I think there will enough bend in the pipe and play in things for it to slide into place, with a bit of persuasion.

[ARH]

If the pipe is that old and damaged chances are the second you try to bend or cut it will crumble, especially if it has been exposed to uv. Why not replace it all?

[JoshSm]

If you really wanted to you could grind the ridge out of one of the couplers, convert it to a slip joint so you can assemble the thing, then have a load of mess with the glue as you bond it.

Another option depending on the damage is to cut a coupler up and turn it into a patch.

[JoshSm]

It's also possible to get slip/expansion couplers for solvent weld, I've used those to put assembly joints into things. Basically a coupler with solvent joint on one side and a push fit on the other, but sized for a solvent pipe. Deliberately made to give wiggle room.

[RGG]

boyse7en said:

I need to replace a piece of damaged waste pipe. It's about 2m long and is solvent welded into a 90deg elbow at each end.

It's been in situ about 30 years so I doubt that I'll ever be able to "unweld" the elbows to remove it, so my plan was to cut out the damaged bit and replace it, with a straight coupler at each end to join it to the old pipe.

But then I realised that I won't be able to fit the new pipe in, as it will be exactly 1/2 a coupler too long until it is in position to slide over the old pipe.
How do I get around the problem? Can "split the difference" and have the pipe going only halfway into the coupler at each end, or will that not seal?

If your image reflects the actual - 1) cut above one or both 90 degree joints - or 2) one 90 degree joint and a suitable section of the horizontal pipe - result would be standard joints suitably solvented.

[TVR Sagaris]

I agree with the above posters that it would probably be better to cut more out and start again, but if you can't then you could also use flexible rubber joints around the new pipe. E.g. Fernco ones:

[Black_S3]

JoshSm said:

If you really wanted to you could grind the ridge out of one of the couplers, convert it to a slip joint so you can assemble the thing, then have a load of mess with the glue as you bond it.

This is the way I'd go but it does require a bit of practice and even then you still end up with glue everywhere or worse the glue takes before youre all in place and you end up out of pipe to repair so be very careful if the amount of good pipe you have to play with only allows you one attempt.

The way the OP suggested of not going full slip but the difference split to say half depth will also work as long as its not hanging on a ball hair and the pipe is well supported either side of the joint.