We recently installed a new countertop and kitchen sink (which is built into the island). The sink is 2 inches deeper than the old sink, so we had to redo the plumbing to make everything fit. We used ABS pipes, a new out of package p-trap and ABS cement. Currently we have ONE joint that will not stop leaking. It is the joint right off of the disposal (see picture).

Things we have tried after initial installation:

  1. New /different pipe
  2. New / different washer (right now we have a Polyethylene washer designed for a slip nut)
  3. Teflon putty (TFE paste)

At first it only leaked when there was a rush of water (like if the sink was full and I released the drain stopper). After we applied the TFE paste, it leaks whenever we turn on the water. Just a drop every 5 minutes or so. I am out of ideas. What advice can you offer?

Joint that is leaking under kitchen sink built into island

  • 1
    The washer came with the slip nut. It is a tapered washer installed with the thicker edge facing the slip nut. Commented Aug 5, 2020 at 21:21
  • 1
    Is the tapered washer snug on the pipe for the dishwasher? The tapered end while good and snug on the pipe should just fit inside the pipe you are draining to with the dishwasher pipe extending beyond the tapered washer. If the taper washer is not snug almost hard to go on the dishwasher pipe it is the wrong size and that may be your problem. Don’t over tighten plastic fittings two much and they strip out.
    – Ed Beal
    Commented Aug 5, 2020 at 21:46

2 Answers 2


Neither tape nor putty should be used with a plastic compression joint. Tailpieces like that sometimes have flat washers when you probably need a tapered one--it should be the same as those at the other joints.

Have you gone beyond hand-tight with the nut? Sometimes an extra half-turn with a large pliers seals the deal. Just support the pipes when you do it.


As mentioned in the comments you first need to make sure that you have the proper washers assembled correctly on the tailpiece coming out of the disposal.
Then, remove the P trap and attach the white drain pipe in the picture to the tailpiece first before attaching the P trap. This will take any potential lateral pressure off the joint that's leaking giving you a better chance of a secure connection.

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