Removing a Compression Fitting

To do it, you need two pairs of locking pliers: one to turn the compression nut and one to hold the pipe and prevent it from turning along with the nut.

Tighten one pair of pliers onto the compression nut and the other pair onto the pipe entering the fitting. Turn the nut counterclockwise while you hold the pipe steady. It may take a little more effort than you expect to unlock the nut and get it to turn. Once the nut turns, you can often unscrew it by hand to separate the fitting, and all that's left to do is remove the ferrule from the pipe.