I just replaced a faucet and drain on a sink which involved taking out and reinstalling the p-trap. When removing the p-trap I noticed the union nut was very tight. After my re-installation - hand tight - it leaked. Adding a bit of pipe dope and tightening a bit more with a wrench I heard some subtle creaking/(cracking?) and it's still leaking slowly. I'm assuming something may have cracked and I'm ok with replacing it if necessary, but some questions:

  • How do I know if something cracked and needs replacing?
  • Should I replace just the p-trap side of the drain with the union nut or cut away and replace the connector on the wall side as well?
  • If replacing the connector on the wall side, what parts should I use and how should I do the install? I dislike the way that things are cemented since it means cutting a little more pipe each time I need to do a replacement.

enter image description here

  • 1
    First, that's ABS pipe - important to get the right glue, etc. if you have to go that route. Jan 9, 2015 at 21:57

1 Answer 1


You probably won't be able to replace just half of that trap as different manufacturers use different threaded connections at the union. Assuming the "lock ring" you referred to is the union nut (the large nut connecting the two halves of the trap), hand tight is not enough so tightening it carefully with a tool was appropriate. Unfortunately it is common for the nut to crack, causing a leak at the union.

I would cut the black horizontal ABS pipe downstream of the trap and replace the trap with an adjustable P-Trap. This will require a glue joint, but will leave you in a much better position for future repair or replacement when necessary. Use only ABS cement.

enter image description here Remember, hand tight is not enough. Use adjustable pliers to tighten (but not over tighten) all slip-joint fittings.

  • Yes, the union nut and ABS. Thanks for bearing with me :) Do you have a link or example of the parts that are needed? Not sure what sort of fitting I need on the downstream/wall side to allow the slip joint to work with it.
    – Jonathan
    Jan 9, 2015 at 23:55
  • The pic I included is what you need, ask for an 1 1/2" ABS adjustable P-Trap kit, it should come complete. The only other stuff you might need is a small can of ABS glue, and maybe a tailpiece extension for the vertical pipe (in case the new trap ends up lower). Go to a good hardware store or plumbing shop (not a big-box like H.D.) and you will get the parts and assistance you need. Jan 13, 2015 at 2:46

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