I just moved into a new house and am having a problem where the sink takes longer than normal to drain. Also, while using the shower, there is a gurgling from the sink.

I tried some drain cleaner, but these were supposed to be newly installed lines. So I'm wondering if the way the p-trap is installed is the issue.


  • 1
    Was this configuration done this way to accommodate cabinet drawers or wheelchair accessibility? Check out this video of an Ikea cabinet installation and note how they did it. youtube.com/watch?v=Oiun5EiBhIc
    – Frambot
    Dec 14, 2021 at 23:38
  • 2
    Is this a vessel sink?
    – Kris
    Dec 15, 2021 at 2:16
  • Yes, it is a vessel sink.
    – Jon Moore
    Dec 15, 2021 at 3:41
  • Show us the pipework behind the back wall of the cabinet
    – Caius Jard
    Dec 15, 2021 at 11:33
  • "while using the shower, there is a gurgling from the sink" - that has nothing to do with any pipes you can see. But, can that trap suck itself dry, or the sink gurgle itself? IDK maybe. It's deff backasswards in two places.
    – Mazura
    Dec 15, 2021 at 18:22

2 Answers 2

  1. Didn't know about trimming tailpices to fit, leading to odd arrangement with more pipe than needed.
  2. And more critical; that's an S trap now. The pair of vertical elbows at the wall entrance is a definite no-no.

Is this a rental? There has been some seriously unlicensed plumbing going on here, I'd say.

The elbow entering the wall should be turned towards the sink, "just off horizontal" in a "slopes to the drain" manner. 1/4" per foot. Unfortunately it's glued, so correcting that will be a bit of work. Might choose a diferent angle of elbow - 60, 45, 30 or 22.5 to point more directly at the sink.

The sink tailpiece should be extended and the trap lowered so that the exit of the trap is 1/4" per foot of pipe higher than the entrance of the wall drain, not several inches above the drain entrance to the wall. If it's more convenient, you can run the trap exit straight back to the wall and make a horizontal corner there (using the 90 you already have) to a pipe along the wall leading to the drain entrance.

Tailpieces and extensions can and should be trimmed to make the plumbing reasonably direct.They come long, and can be slid a certain amount, and can be trimmed if they are still too long. Aim to trim them so most of the adjustment range remains, rather than making them just reach.

There might still be a venting issue out of sight in the wall, but that addresses what we can see is wrong with the trap setup.

Not great, the angle is such that the green (trying to show going directly to the drain) and the purple (trying but mostly failing to show "back to the wall and turn to follow the wall to the drain" look mostly the same. But an attempt...

enter image description here

  • 2
    would this violate the 24 inch max sink drain to weir rule? Not sure if that rule is applicable in all areas but it may be.
    – HoneyDo
    Dec 15, 2021 at 0:03
  • 3
    You're assuming that's a floor, per your answer. To me, it looks like the underside of a counter, with a vessel sink on top of it, so I very much doubt that the 24" rule is in any danger of being exceeded.
    – Ecnerwal
    Dec 15, 2021 at 0:07
  • 2
    Good point, but still something OP should watch in lengthening the standpipe.
    – HoneyDo
    Dec 15, 2021 at 0:13
  • Thank you guys. I knew it had to be that set up.
    – Jon Moore
    Dec 15, 2021 at 3:43

@Ecnerwal hit several of the big issues here but there may be more.
There is definitely a venting problem. A good rule of thumb on venting with a P trap is if the P trap can't "see" the vent it's a problem. The following illustrates how a vent should be configured relative to a P trap:
enter image description here

The alternative here is to add an air admittance valve (AAV) on the crosspiece after the trap about 6 inches out which should meet code - but check.
Second, in the pic we can't tell the length of the tailpiece going up through the floor/countertop but the distance from the sink drain to the top of the water seal in the P trap shouldn't exceed 24".

enter image description here

The above also illustrates the illegal S trap mentioned by Ecnerwal.

  • 1
    There's definitely a venting problem due to the S-trap. The pipes in the wall may be fine and properly vented, but the S prevents the vent being in the right relationship. The pipes in the wall might also not be fine, but there's no way to tell from what we have to work with here.
    – Ecnerwal
    Dec 15, 2021 at 0:05
  • 2
    Agree there's a venting issue, although that would not be a cause of the slow drain (a blocked/inaccessible vent actually makes a basin drain faster). Dec 15, 2021 at 14:30
  • @Nuclear Hoagie - Are you sure about that? For water to drain it needs to pull air into the line. Without good venting the draining water builds up negative pressure (vacuum) which pulls the air through the P trap clearing the water seal all of which slows draining.
    – HoneyDo
    Dec 15, 2021 at 16:44
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    @HoneyDo It's a common misconception, with many people using the "inverted soda bottle" analogy to illustrate water glugging out of a drain. The problem with that analogy is that there is no such thing as a fixture with only one inlet/outlet - all fixtures have a separate inlet (the basin) and outlet (the drain). Air can always follow liquid down the drain to equalize pressure, with or without a trap. The trap just keeps the P-trap from being sucked dry. In fact, a basin drains faster with no trap, as water gets "pulled" down the drain by the moving water further down the pipe. Dec 15, 2021 at 16:51
  • @Nuclear Hoagie - Your point about a sink draining faster with no trap (or an open trap) is right on - however, when the water seal in a P trap is lost, it doesn't stay that way. Without proper venting, when the water seal once again forms, draining a sink full of water will be slower. But I agree that the venting is only one issue here. If the OP follows the steps outlined in Ecnerwal's and my answers it should solve the slow drain problem.
    – HoneyDo
    Dec 15, 2021 at 17:43

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