How to undo a bond between mated pieces of pipe
I am remodeling my bathroom and have to move the toilet slightly. Is there a process I can use to "unglue" a 3-inch PVC pipe joint that has been in place for 25 years?
— Ted, Moriah, NY
Richard Trethewey replies: Soldered joints in copper pipe are easy to reheat and take apart, but there's nothing that will dissolve the solvent bond between mating pieces of PVC. The easiest solution is to cut out the problem joint and replace it with a new fitting, joined to the old pipe with a coupling. If this is absolutely not an option, as seems to be your case, you can try to cut out the pipe stub embedded in the fitting and leave the fitting in place.
This requires a bit of artistry with a hacksaw and chisel. First, using the hacksaw, cut off the pipe flush with the fitting, which you leave in place. Now put the hacksaw blade into a blade holder and slowly make two cuts about a half inch apart through the wall of the pipe inside fitting. Take care not to nick the inside of the fitting. Then, using a sharp chisel, cut a notch out of the pipe, being careful not to let the chip fall into the drain. Make additional cuts about every half inch and continue chiseling and catching the chips until the pipe is gone. It's not going to be easy, but if it's the only choice you've got, give it a try.