I am trying to install a new vanity and have run into some trouble trying to fit the plumbing needed under the sink because:

  • The vanity is small
  • The plumbing goes directly into the floor
  • All the pipes are really tight together limiting the amount of space for PVC
  • The PVC drain pipe leading into the floor is not straight up-and-down (it's crooked)
  • The sink drain and drain pipe are located weirdly with respect to each other.

The following is my attempt at the plumbing, but I believe that the distance from the p-trap's union and the elbow is not up to code. Also, to get the old (crooked) drain pipe to line up with new piece of PVC, I cut the drain pipe at an angle which I assume is probably not the correct solution to the problem. Finally, the sink is now gurgling or gulping when water flow is strong and it wasn't before.

enter image description here enter image description here

How can I improve my current design and could my current design have caused the gurgling/gulping?

Note: There is a vent that goes from the crawl-space below the bathroom to the outside. I am assuming that the sink is connecting to that. Also, I have not checked if it is clogged but it was working fine before I removed the old vanity so I am making the assumption that it is still working.

EDIT: Here's a picture of the setup before I removed the old vanity. Please note that I had already removed the sink so the sink drain is not there enter image description here

  • 1
    My guess is that the sink drain is actually connected to your vent instead of a drain. Maybe you can add an air admittance valve to stop the gurgling? Other people on here are actually know plumbing, so do whatever they say.
    – Dotes
    Commented Apr 22, 2019 at 3:16
  • @Dotes yeah, i was thinking that might be a solution but i (luckily) took a picture of what the plumbing looked like in the old vanity and there is no AAV there either and it worked fine. Unfortunately, the plumbing in that vanity was (I'm told) a horror show as well so I couldn't copy it :/
    – Gab
    Commented Apr 22, 2019 at 21:22
  • maybe post a picture of the way it used to be too? My only guess if it used to work is that the old sink had an internal overflow drain that was helping with the venting, but I guess that a picture probably wouldn't show that.
    – Dotes
    Commented Apr 22, 2019 at 21:39
  • @Dotes I've added the picture anyway for good measure
    – Gab
    Commented Apr 23, 2019 at 4:09
  • Can't help you with the gurgling, but it was hard to get together because there's no horizontal slip coupling. It had to line up perfectly with that swing elbow or you'd've been sol.
    – Mazura
    Commented Apr 23, 2019 at 4:34

1 Answer 1


Not sure how many bends (90's) your drain makes after the vanity, but if only one, you could stick a 90 on the drain coming from the floor of the vanity, and have it sloping up and point towards the back corner of the vanity. You could then run another 90 straight up with an AAV at the top of the pipe and have your trap tie into this vertical pipe significantly lower than the AAV, giving you a long enough pipe after the trap before a vertical drop. This may alleviate the gurgle noise but I do not know for sure. Your trap should be draining into a pipe that has a vent on it, so that when the water does a vertical drop it doesn't cause suction on the trap and pull water from the trap causing gases to escape from the sewer system into your house.

  • Thanks for the answer. So, I went into the crawlspace and saw that this drain is connected to a vent stack (after a few twists and turns). Shouldn't this be enough to properly vent it?
    – Gab
    Commented Apr 23, 2019 at 15:57
  • 1
    I think the distance from your sink to the vent is too great with the amount of turns that are involved with the current set up. I am with Nik on this one. Angle the plumbing from the bottom of the cabinet over to the side run a stack up with a sanitary tee to except the drain and then on top of that an air admittance valve as high as you can go.
    – Alaska Man
    Commented Apr 23, 2019 at 19:07

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.