After installing a new sink water backs up too quickly. If I remove the whole construction and pour directly into the sewer line it flows fine, so no line clog.

I think I did mistake in positioning p-trap. What's wrong, how to fix it?

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  • I have two questions, why 2 traps and why is the vent taped close with duct tape. I have a feeling it is leaking am I correct?
    – Gil
    Jul 10, 2021 at 2:15
  • @Gill it's a double sink. Vent taped as the previous install had no vent and I was experimenting to see if vent affect flow in a bad way. Found no difference.
    – Pavot
    Jul 10, 2021 at 3:38

1 Answer 1


It probably not have much effect it is in the wrong place and it is low enough that it could leak. I would start by eliminating one of the redundant traps and see if that helps. When you do remove the tape and place the vent as high as possible. and in the correct location after the trap.

  • I'm not seeing the 2nd p trap and the non working vent appears to already be after the trap, coming out of the tee that goes into the wall. Jul 11, 2021 at 0:21
  • The picture shows the drain from the trap going down, under the red tubing then back up to the wall, this forms a trap. Maybe I am seeing something that is not there.
    – Gil
    Jul 11, 2021 at 1:55
  • It's hard to tell without seeing what's on the other side of that wall. Unless its something very unusual there should be another tee with one side going up to the roof vent and the other continuing downward to a larger waste pipe. The pipe coming out of the wall is unusually low to the floor... Jul 11, 2021 at 2:02

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