PVC plumbing help

[moorem]

Hi all. I rebuilt the plumbing under my double kitchen sink using pvc. Every connection I made using primer and cement is bone dry and draining well. The P-Trap, however, is not. It leaks as soon as the trap starts filling with water. It is a threaded 1 1/2" trap I bought at home depot. Should I be using plumbers putty, teflon tape, etc on a connection like this? I always thought threadd pvc was supposed to be left alone. Any help will be greatly appreciated.

[LazyPup]

You should not apply any teflon tape, dope or glue to the slip joint fittings on the P-trap, end waste or tailpieces.

As you stated, PVC slip joints should fit water tight with hand pressure or at best a light turn with slip joint pliers.

If you are having leak problems there are two things you should check.

Examine the tubular pieces to see if there is excess mold sprue lines.
The sprue is the bit of excess plastic that is pushed out of the mold during processing. Normally it is cleaned off, but occassionally you will find some PVC fittings with the excess plastic lines down each side of the tube. Normally if you lightly scrape the outside wall of the tube you can clean off the excess plastic.

Check the compression sleeves in the slip joints. You may have gotten one backwards (which is a very common problem.)

Examine the compression sleeve and you will see that it has a wedge shaped cross section. Make sure the thick side of the sleeve is toward the nut, and the thin side toward the end of the pipe. As the male end of the pipe is slid into its mating female part of the connection, the wedge will fit between the two pieces of pipe and when the nut is drawn up it pushes the sleeve into the joint making it water tight.

If the compression sleeve is accidently put on backwards, the thick part hits the mating pipe and actually pushes it away as the nut is tightened. In addition, the sleeve wedges under the nut causing friction and giving a false sense that the nut is tight.

[moorem]

thanks, LP. I disassembled it and put it back together following your advice and it's fine. Thanks!

quote:Originally posted by LazyPup

You should not apply any teflon tape, dope or glue to the slip joint fittings on the P-trap, end waste or tailpieces.

As you stated, PVC slip joints should fit water tight with hand pressure or at best a light turn with slip joint pliers.

If you are having leak problems there are two things you should check.

Examine the tubular pieces to see if there is excess mold sprue lines.
The sprue is the bit of excess plastic that is pushed out of the mold during processing. Normally it is cleaned off, but occassionally you will find some PVC fittings with the excess plastic lines down each side of the tube. Normally if you lightly scrape the outside wall of the tube you can clean off the excess plastic.

Check the compression sleeves in the slip joints. You may have gotten one backwards (which is a very common problem.)

Examine the compression sleeve and you will see that it has a wedge shaped cross section. Make sure the thick side of the sleeve is toward the nut, and the thin side toward the end of the pipe. As the male end of the pipe is slid into its mating female part of the connection, the wedge will fit between the two pieces of pipe and when the nut is drawn up it pushes the sleeve into the joint making it water tight.

If the compression sleeve is accidently put on backwards, the thick part hits the mating pipe and actually pushes it away as the nut is tightened. In addition, the sleeve wedges under the nut causing friction and giving a false sense that the nut is tight.