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I am installing a new bathroom sink and it is leaking in two parts, at the faucet drain and at the p-trap. I will ask separate questions for each of these as I believe it is a different solution at both sites (where its leaking). This is all 1 1/4" plumbing. Here I will ask about the p-trap leak.

The installation looks like this:

entire install

Here is where the p-trap leak is occurring (at the junction between the p-trap and the drain/outlet (the long pipe going into the wall):

p trap leak

As you can see, this is a brass p-trap that I bought as part of a kit, and it only came with a nut (no washer) for the trap-outlet connection:

see, no washer

It might be hard to tell from that photo, but at the end of the outlet pipe, about 1/4" away from the end of it (where it goes down into the p-trap) there is a metal "lip".

I tried adding an 1 1/4" rubber washer over the lip but then I can't screw the nut down onto the trap threads. And (at least in my mind) it doesn't make sense to attempt to place a washer in the ~1/8" space between the lip and the end of the outlet pipe.

Does my installation look correct? Am I missing a washer somewhere? Why would this joint leak? I've unscrewed and rescrewed it multiple times, and tightened it considerably and it leak like a sieve.

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You should have a washer for the contact between the J bend and the wall tube. The threads compress the washer against that metal lip and the wall of of the J bend. When you join the parts, there is not metal on metal contact; the washer forms a seal. The threads to the nut is the only metal to metal contact.

Sometimes P-trap kits from the hardware store are missing pieces due to customer returns or customers stealing a component from a kit. In my experience, the plumbing aisle tends to be chaotic due to confused DIYers.

P trap washer

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  • Oh man, so I need to place a washer in between the underside of the Jbend and the top of the ptrap?
    – hotmeatballsoup
    Sep 21, 2022 at 14:45
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    Yes, the washer goes on the wall tube up against that lip you're talking about. It slips on there and is held by friction while you assemble the rest of the trap. It is usually tapered which allows for some slight angle adjustments, but the closer to square the better for that connection.
    – Barrett
    Sep 21, 2022 at 14:51
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    It can be a plastic part too. And they sell the nuts / washers/ plastic parts individually in bags if you look hard enough
    – gbronner
    Sep 21, 2022 at 14:54
  • I can confirm this solution worked great -- thanks again, and thanks for posting the pic which was helpful to someone of little brain (like myself).
    – hotmeatballsoup
    Sep 21, 2022 at 16:49

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