you cut out the old pipe and replace with new. the joints won't come apart, just cut it back to where you need and put inthe new section.

It cannot be done. Although we call it gluing in fact the process of gluing PVC is a chemical welding process where the pipe is fused to the fitting.

The proper solution is to cut out the bad pipe and fittings and replace them.

As a side note, I once worked with a really strong weightlifter type guy who I saw pull apart two ABS fittings that had been glued together for about one hour.
I was impressed.

Hi, Before I would cut the system loose I would dry the joints and put the glue on over the joints. As noted above it is not glue but a chemical process the fuses the pipe together, it will probably fuse the leak shut It worked for me and beside what do you have to loose by trying?
Good Luck Woodbutcher