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I have p-trap entry in drain at 16" above the floor. However, vanity that I got has lower drawer which has top at about the same height. There is also about 4" clearance behind drawer. I was told that the only way to install p-trap would be to cut back of the drawer.

So I wonder if it's really the case. Can't drain entry be just raised with some additional elbow so p-trap enters it 6" higher? Any other options? Is it possible, for example, to install p-trap sideways so it fits into those 4" behind drawer?

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  • I have my P-Trap below the kitchen floor. The basin drain goes straight down into the basement, and the trap sits between the floor joists. This may be an option if everything is located appropriately.
    – Chris Cudmore
    Aug 15, 2012 at 12:44
  • Some codes limit the length of the tailpiece to something like 24". It's intended the tail piece be as short as practical. I think the limit is because falling water could develop enough momentum to flush out the trap.
    – bcworkz
    Aug 15, 2012 at 21:50
  • Could you do a 90° bend coming from the wall and pointing up, then do a 90° bend pointing horizontal? That should give you more room for the p-trap. Not sure if that passes code. Anyone?
    – user35582
    Apr 14, 2015 at 1:18

7 Answers 7

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  • As long as the p-trap is lower than the drainage from the basin then you can install it. It can also be lower than your exit pipe you need to drain into
  • You attach the p-trap directly to the drainage and manuever the p-traps exits into you existing drain.
  • It is not ideal to have the p-trap below the the exit drain because water gravity has to force the water out instead of it flowing downwards naturally. They both work and have seen it many times. But essentially anything below already creates its own p-trap- so using another is redundant.
  • If the p-trap is to tricky just create your own loop from pvc
  • For ease of manageability you can use a flexible waste connector pipe from the p-trap to your drain pipe.
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Some twisted to fit p-trap

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Small pcv p-trap

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A sideways p-trap is useless, you might as well connect it straight line.

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Theory of a p-trap

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You might want to look into s-traps also

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  • 2
    and +1 for showing what does not work. Sometimes the flex connectors do seem necessary, but they should be a last resort since they are more prone to collecting bits of waste/hair that can clog a drain and are problematic if you have to snake out a blockage.
    – bib
    Aug 15, 2012 at 11:51
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    as sideways, I meant turned along vertical line so trap is closer to wall but still pointing down. It's curious to see that someone installed p-trap actually sideways.
    – Uncle Meat
    Aug 15, 2012 at 14:51
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    S Traps are prohibited in BC (Canadian National Code as well), so make sure they are approved where you live. I believe that the issue/concern with them is that they promote self-siphonic action causing the seal to break.
    – pdd
    Aug 15, 2012 at 17:20
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    All modern model codes prohibit S traps. They used to be SOP many years ago, but as pdd explains, it's a less than ideal design. +1 to bib re: flex pipe. And sideways P trap! Too funny!
    – bcworkz
    Aug 15, 2012 at 21:55
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    That is really interesting about the s-traps ; Never had any issues with them loosing water seal.
    – Piotr Kula
    Aug 15, 2012 at 22:41
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Here is what I ended up with. It doesn't contradict the code and inspector signed all the papers. I am not sure if he really looked at it, though.

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  • looks good to me
    – Edwin Buck
    Sep 28, 2012 at 19:13
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    It's fine - stupid looking, but fine.
    – The Evil Greebo
    Nov 15, 2012 at 1:32
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I had a similar situation to you and ended up doing what you see in the picture below. The old vanity did not have a bottom drawer, so the bottom of the p-trap was below the wall drain pipe. I got the parts necessary for this in an s-trap kit from home depot, and then got a 1' section of PVC that I cut with the miter saw to join the elbow to the trap.

sink trap

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  • That looks good. Is it allowed by code and was it inspected?
    – Uncle Meat
    Aug 15, 2012 at 14:45
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    It was not inspected, I just did it myself. I brought the picture of the basin and drain outlet to the local home improvement store and this is what the workers there suggested. Seeing as how the trap is there, I don't believe it is a health hazard, but I will claim ignorance on the code aspect.
    – Aaron
    Aug 15, 2012 at 15:09
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    Clever solution, but this is an S trap which is prohibited by modern model codes.
    – bcworkz
    Aug 15, 2012 at 21:46
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I am having the same problem as the original poster. My rough-in drain is 16" from the floor, however my new "modern style" vanity for my ensuite and main floor washroom need clearances above 18". The good thing is both vanities have a 4" space from the back of vanity to the drawers. ( in other words, the drawers are not the full depth of the vanity ).

I was about to give up and call a plumber...but I found a solution from a manufacturer. http://www.canplasplumbing.com/plumbing.aspx?categoryID=383

This solution gives me the ability to make a sharp 90 degree from the wall (copper to ABS) and the install my p trap sideways. The trap is installed below the drain line.

My solution looks similar to the original poster's photo solution but I used ABS and did a 45 and 45 from the sink hole to the trap. It looks like he used 90 and 90 degree turns.

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    A sideways P-trap does not prevent sewer gasses from escaping!
    – Steven
    Nov 15, 2012 at 3:16
  • You should be clear that your sideways P-trap refers to one flat against the back wall, and not horizontal like ppumpkin shows in his answer
    – BMitch ♦
    Nov 16, 2012 at 12:01
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You simply need to install an auto-vent, after the p trap at the highest point of your down down turn. It would be impossible for the s portion of the trap to auto siphon. If auto vents are allowed in your area.

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tail piece off set before p trap connection is ok, similar basin drain off set connection for handicap plumbing. S trap is not acceptable.

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Just use a tail piece extension. Why are you adding all this extra work. Its very simple. If your drain line coming out of the wall is lower than the the tail piece of the fixture its serving, then extend the tail piece with an extender. This is exactly why they make em. All this extra work your doing is 1. Illegal in most states 2. Has the potential for a lot of leaks. 3. Is not necessary.

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    Your answer could be improved with additional supporting information. Please edit to add further details, such as citations or documentation, so that others can confirm that your answer is correct. You can find more information on how to write good answers in the help center.
    – Community Bot
    Nov 27, 2021 at 10:28
  • Assuming that you replying to the original question and not the answer that shows S-trap. 1. If it is illegal anywhere, please provide at least some reference. My research as well as some others answers suggest that it is at most a grey area. Inspector saw it and didn't say anything. Similar things are used in double sinks as well. 2. Why is it more leak prone if all connections are done right? I've been using it since 2012. No leaks so far. 3. It is necessary to avoid cutting the drawer as indicated in original post.
    – Uncle Meat
    Dec 4, 2021 at 1:03

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