pvc kitchen sink problem

[tessbridget]

my garbage disposal was clogged and upon removing the pvc to the drain to clear i noticed that the pvc pipe exiting the wall was cracked completely . i don't know if it was originally like that or it happened when the disposal was installed. how would i repair it?

[LazyPup]

Wow.. a crack in PVC is not impossible as you have discovered but it is a rare problem.

The method of repairing it will really require a bit of a judgement call on your part once you determine the exact location and total extent of the crack.

If the damaged piece is anywhere forward of the trap adapter (P-trap, End waste Kit or tailpiece) the solution is to just replace the defective part or kit.

If the crack is in the "Waste Arm" from the stack to the trap adapter you may be able to just cut out the defective section and replace it by using a short piece of new pipe and a coupling.

If the pipe is cracked close to the Sanitary TEE where you do not have enough good pipe to attach a coupling you will need to cut out the sanitary Tee and replace the Tee as well as the waste arm.

Cutting the vertical riser inside the wall can be a tricky job but here is a little trick that will make it easy. Get a length of nylon masons twine about 3' long and loop it around the pipe where you need to make the cut. Twist the ends of the string around a couple screwdriver handles or blocks of wood to make pull handles, then alternately pull the string back and forth rapidly. The string will cut through the pipe like a hacksaw very quickly.

Make one cut a few inches below the sanitary tee and a second cut a few inches above the tee. Once you have the cuts made you can pull the Tee out, then glue a coupling on the lower section of pipe, install a short nipple of pipe and a new sanitary tee. From the top of the tee make another short length of pipe that is almost the exact length from the sanitary tee to the bottom of the vent cut off. Slip a Fernco coupling on the pipe and slide it down till it is completely on your new section of pipe. Prime and glue the pipe and set it into the sanitary tee, then you can slide the Fernco coupling up over the top joint and tighten it in place to finish the riser.

Now install a new section of pipe from the side opening of the new sanitary tee out to the desired length and glue a new Trap adapter on the end.

You can then connect the P-trap into the trap adapter in the normal manner.

Here is an illustration I just made to help you visualize the layout.

The Waste arm could make a 90 deg turn in the wall and run horizontal to the stack. Depending upon what code is in force in your area the waste arm could be up to a maximum of 6' long when measured on the top of the pipe from the P-trap to the vent.

[Phelps]

I had the same situation once, in a rental!

Cut off the pipe that exists the wall, leaving enough pipe so that a coupling can bottom out up against the sanitary tee...if the crack goes back to it. Then by gluing on the new coupling, the glue itself will literally fuse weld that crack and hold it in place because it is inside the new coupling.

IF the crack doesn't go all the way back to the sanitary tee, then obviously you don't have to cut out any more of that horizontal pipe, (that LazyPup drew) than you have to. But you have to be absolutely certain you can tell that the crack ends where you think it does. Otherwise, simply go back to within about 3/4 inch of the sanitary tee, to cut it. If it does go back to the tee, it is extremely important that you only leave enough stub of a pipe coming out (like 3/4 inch) so that the new coupling abslolutely butts up to the sanitary tee. You must liberally coat the rim edge of that sanitary tee and the backside rim edge of the new coupling, with both primer and glue, as well, to ensure that no water will leak out between the new coupling and the sanitary tee.

My similar repair worked, and I never had one drip afterwards. (And this was done about 1-2 years ago), and I have been back to this rental many times since. I know the problem was solved by it fuse welding.