I recently moved into a new flat and it has 2 sinks that are plumbed as such:

Image of plumbing under the kitchen sinks, showing a bottle trap and a p trap.

As far as I understand, both the Bottle Trap and the P Trap serve the same purpose, so in this case the Bottle Trap is redundant and can be removed, right?

I'm asking as I'd like to get a plumber to remove the Bottle Trap and replace the flexible tube with a proper pipe so that it reduces the amount of cleaning needed and improves flow, and wanted to check that it's the right thing to do before calling the plumber.

  • 1
    There was a question about bottle traps last week and from the comments/answer they are now illegal/against code to install(North America), so removing them and just using P-traps is good.
    – crip659
    Commented May 8, 2022 at 21:36
  • 3
    Pretty clearly UK by the plugs, I'd say. But yes, that one is actually doing no good at all. Not sure how UK plumbing code rules on the pair of sinks - under IPC, if the drains are within 30 inches you only need the one trap for the pair. And the transfer tube should be full-sized and smooth, as you want.
    – Ecnerwal
    Commented May 8, 2022 at 22:23
  • 1
    @Tim - afaik UK sockets are all protected by an "ELCB" (aka GFCI in the US) back in the panel.
    – brhans
    Commented May 9, 2022 at 12:09
  • 1
    @Tim - it's not particularly uncommon in the US to have a GFCI outlet under the sink to plug in a garbage disposal ...
    – brhans
    Commented May 9, 2022 at 13:33
  • 1
    @FreshCodemonger - great idea. Let's legislate for fixing sockets - under the bath, toilet, sink, washing machine, shower... We could even put one outside so we'd know when it was raining...
    – Tim
    Commented May 9, 2022 at 17:01

1 Answer 1


It looks like you have two drains, correct? The picture may be deceiving, but it looks like one trap is lower than the other. You could get away with one trap, but it would have to piped in such a way that both drains are above the trap. Water flows down hill and the trap should be full to prevent sewage gas from coming back up through the drain. Hope that makes sense.

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