PVC pipes are a great asset to do-it-yourself plumbers because they join like a dream. Next to ABS pipes, PVC pipes are the most secure pipes that you can join with such ease. That advantage turns into a disadvantage the moment you try to separate the pipes and remove the PVC glue. Doing so is truly a challenge, but there are a few methods that possibly can help make this happen.
How PVC Pipe Glue Works
PVC glue is not glue. The term glue is a convenient handle, but it minimizes the power of a substance that works at the deepest level of PVC's molecular structure.
White glue, wood glue, and hot melt glue are examples of glues that sit on the surface of the materials and harden. The hardened glue grips one material to the other material. PVC glue works completely differently.
PVC glue is a solvent that melts the two pipes and bonds them together. As soon as PVC glue is applied to PVC pipe, it immediately works on the top layer of the PVC, softening and dissolving it. When a second piece of PVC is pushed against the first piece, the softened plastic of each piece bonds with the other. The result is a continuous section of PVC. In many cases, the joint is stronger than the pipe itself.
The good news is that you might be able to catch the pipes in time if you just now joined them. Another factor that can work to your advantage is that PVC pipes are sometimes poorly joined, making them good candidates for separation. In a hurry, the plumber or do-it-yourselfer may have only partially applied the PVC glue to the joint.
Equipment / Tools
- Heat gun
- Tongue-and-groove pliers
- PVC pipe cutter or hacksaw
- Thick gloves
Cut the PVC Pipe
Cutting back the PVC pipe to a new point is actually the best way to separate PVC pipes and remove the glue. Professional plumbers usually will cut away PVC pipe rather than try to separate it. PVC pipe is soft and easy to cut. Unlike copper pipe, it's inexpensive to replace.
Use a hacksaw or a PVC pipe cutter to cut off the section you would like to separate. Make sure that you leave enough room to fit the new coupling, elbow, or other PVC fitting.
Twist the PVC Pipe
Twisting the PVC pipes in opposite directions may provide enough torque to separate the two pipes. Two tongue-and-groove pliers working against each other, one on each side of the pipe joint, may help to break the bond.
PVC pipe has low collapse strength when compared to other pipes. For example, 2-inch diameter schedule 40 PVC pipe is rated at 225 pounds per square inch before it will collapse. Be careful about applying pressure to the pipe from pliers.
Heat the PVC Pipe
Even though it wasn't heat that initially fused the PVC pipes, it was a chemical process similar to heat. So, by applying heat to the pipe with a heat gun, you may be able to soften the joint enough to separate the pipes.
Start with the heat gun on a lower setting and begin to heat up the PVC pipe. As the pipe heats up, work on the pipe with the pliers by twisting it away from the other pipe. It's a slow process, so be patient. In many cases, you may have to sacrifice one pipe by breaking it away from the other pipe.
Remove Glue From PVC Pipe
If you do manage to separate the PVC pipes, you may want to try to remove the glue from the pipes. Fortunately, PVC pipe glue isn't like other glues: It's very watery and doesn't lump up. The surface of previously glued PVC pipe will be distorted and colored purple (because of the color of the glue).
Sanding down the distortion and sloughing away the purple color is the best way to remove the glue. Start with sandpaper in the #220 grit range and work up to finer-grit sandpaper to smooth away any grooves.