We recently renovated our bathroom in our apartment building and noticed the bathroom sink wasn't draining poorly. Our contractor said it just needed to be unclogged, which he said he did and now it appears to be draining properly. However, upon inspection of the pipes underneath the sink and enclosed in the vanity, we noticed the configuration of the pipes looks strange, like a roller coaster with multiple loops. We were told they did it that way to accommodate the drawers so the bottom drawer would close since it didn't have a cutout to accommodate the pipes. We are concerned that the pipes may not be be up to code and have recently heard about P trap drain and was wondering if our pipes have that trap or any trap for that matter. Any possibility of this configuration causing blockage/backups again in the future and possible leaks/burst pipes also?The top of the pic is where the pipe is connected to tail piece of the sink and it loops a couple of times before going into the drain line in the wall. This is all housed within the vanity.View from other side of the pipes.

  • 1
    Quick tip: when you see a single section of pipe with both ends facing up, it is most likely a trap.
    – user4302
    Feb 8, 2017 at 0:39

2 Answers 2


It looks like the original installer didn't quite have the correct combination of pipes and and fudged things a bit. It's perhaps not optimal but fine to leave as is.

There is a trap which is the bit that goes down and then back up in a classical U-trap. There is water in that section to block the foul smelling air coming back up the drain.

  • I have seen a lot worse over the years. As ratchet Freak points out there is a trap and it works when clean so it is fine.
    – Ed Beal
    Feb 7, 2017 at 14:02
  • Thanks Rachet Freak & Ed Beal for your comments. Was just worried that all those bends and compression joints are bound to fail or clog.
    – Lucky Dog
    Feb 7, 2017 at 17:50

This is equivalent to an s-trap and is not allowed by code. I'm guessing this was done without a plumbing inspection. It is not dangerous unless you fill up the sink and it all drains at once. This might cause a siphon effect which could empty enough water from the trap to allow sewer gasses to escape, defeating the purpose of the trap. If you slowly add a little water after draining a filled sink it will restore the trap to safety. When you go to sell your house this will probably pop up as an issue with the home inspector (if they are any good).

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.