Removing Plumbing Fittings
When you work with PVC, particularily when you're replacing something, the less you can do is often the best you can do.
Removing a defective piece of equipment on this 6" line doesn't leave enough visible pipe to safely tie into the new the new equipment. But, if you can cut the old coupling in half and re-use the pipe inside, that will give you just enough pipe to attach a new and secure fitting.
Oh, and did I mention there is a quarter of a million pounds of water just on the other side of this 6" valve? One slip and all that water could be yours. Instantly.
First, use a standard PVC saw blade to cut a slit in the old fitting. You can gauge the depth of the fitting by eye or if a blue or gray glue was used originally, you'll have a reliable depth indicator.
And, always, always, always consider the curvature of the pipe and guide the blade accordingly. Be decisive here, but gentle. Cut a second slit parallel to and about 1/2" away from your original cut. If you should happen to saw either slit a little too deep, glue will generally fill in the void when you attach a new fitting.
Using your smallest flat screwdriver, gently tap-hammer the tool edge between the two PVC surfaces. It helps to use two screwdrivers, using the smaller to separate the pipe layers and the larger screwdriver to both hold them apart and bring additional pressure on the unwanted bits.
Wear safety glasses, these PVC pieces can fly off like sharpnel.
You can use a heat gun to soften uncooperative small bits, but heat quickly distorts PVC pipe and once pipe is out of round, it may never again be water tight.
With a little chisel practice, particularily when PVC cleaner wasn't used originally, you'll be able to get a fitting off in one piece.
Remember also, that if this repair attempt should fail because the pipe chips or cracks unexpectantly, you can reverse this same procedure (albeit more carefully) to dig pipe out of the inside of a fitting; in this case, by removing the 6" pipe from the valve socket.
More often than not, you'll be left with small nubbies and gouges that would prevent easy and secure installation of a new fitting. To prepare the pipe, use a small hand sander or rasp to smooth the surface of the pipe.
When you've had to prep a pipe in this manner, its recommended that you use a full bodied glue (gray or blue) rather than the medium bodied clear glue to prevent leaks around the fitting.
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