Can you unweld pvc joints?

If you can sacrifice the outer part (the U-bend here), it usually can be cut and carefully peeled off, and the remainder cleaned up for re-gluing.

PVC pipe solvent "welding" is not really welded, just glued with solvent penetration.

more like fused or "melded" : ) ...no glue or adhesive used. it's closer to welding than gluing...if you think about it!

p_z

There's a nifty tool made to ream out plastic pipe joints for reglueing sold at good hardware stores. Ask there. Tom

I have always been able to with enough torque. But I wouldn't start a fight. If its a tight space and I probably can't torque it, I'd just cut it and buy a new piece. Time is money.

The drain pipe is ABS not PVC and if it was 'glued' correctly, no you can't undo it. Be sure to use the right type 'glue' when redoing.

Harry K

That requires cutting off the fitting to begin with. I really have never seen a reason to do that other than to fix a pipe that has broken at the fitting. Given room to work, just cut out the problem and replace. Those fitting are in the 'cheap' range.

Harry K

DWV pipe can be either black ABS or white PVC depending on the code for the local jurisdiction. Much of the US uses PVC, here in Ontario, Canada ABS is mandated but PVC is used for underground piping which makes for some interesting interconnections.

Interesting to note that when Home Depot opened here in Canada, the first time I visited a store they had only PVC DWV piping, which was illegal. This didn't last, but it took a couple of weeks before they actually replaced their stock with ABS.

Huh? PVC cement is a solvent glue.

No. "Welding" is the fusion of the same materials. PVC cement is not PVC, so it is not at all like welding, because the joint filler material differs from the bulk material. More like brazing or soldering, if you want to analogize.

The solvent melts the plastic so that it fuses to itself. The solvent acts as heat to soften the PVC. That is not a glue property...with all do respect.

If you peel a joint apart, it is apparent that the only fusion is between the cement filler (not PVC) and the bulk PVC, and that the depth of penetration is very shallow.

If you peel a joint apart, then it wasn't a good joint to begin with.

The fusion is just that, the solvent and PVC become one and the same... there is nothing to separate.

Polymerization is quite weaker in the solvated portion versus the original bulk. With some destruction, the components tend to separate there.