New bathroom sink and P-trap question

jon-hAugust 11, 2010

Hi all,

I purchased a new bathroom vanity top, sink, and faucet and installed it on my cabinet earlier today. The new sink is deeper than the one it replaced. Maybe a little too deep...

The drain pipe coming out of the bottom of the sink extends below the drain pipe on the wall. I thought about cutting the drain pipe from the sink, but even if I cut it all the way to the pop up assembly housing, it's still a bit below the outlet. Which will prevent me from installing an off-the-shelf P-trap.

Someone suggested I install the "J" part of the P-trap in reverse, which would allow for the necessary clearance. If I did so, would this be up to code? If not, what are potential problems that can result from such an installation?

The only problem I can think of is that there might be a bit of left over water in the pop-up assembly housing. Not sure if that will do any damage though...

Here are some pics from two different angles to illustrate what I'm talking about...

Note how the pop-up assembly (cast housing) is almost level with the drain pipe in the wall:

Another angle:

If there's nothing that can be done, I'll be removing the vanity top and sink and will be looking for something shallower.


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A plumber can move the drain line for you

    Bookmark   August 11, 2010 at 8:38AM
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If reversing the trap makes it fit, I'd go for it.
The connection between the tailpiece and J-bend may be more prone to some leakage (as well as the pop-up lever) if not tight or properly aligned, and with the bottom of the bowl so close to the level of the drain, you may notice that the lav does not drain as quickly as before.

    Bookmark   August 11, 2010 at 12:46PM
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jon-h you have identified the problem.
There is not much height left.
Using the drain pipe in the wall is hard because of this.
I'm unable to visualize right now how a P trap can take less height when "reversed".

Anything that raises the position of the pop up nut in the sink tailpiece will do a lot of good here.
I'm assuming you will keep the pop-up.
You could also just remove it and buy a shorter sink tailpiece.
They sell hand press drain popups too, so you could still have a shiny chromed popup drain stopper which you press down by hand, and press again to open, instead of a rubber stopper.

Someone who is comfortable with cutting metal can shorten that sink tailpiece (threaded pipe) for you.
I did this in my bathroom.
It allowed me to keep the popup assembly with the pull handle in the back of the faucet above deck.
It is a lot of finagling but it is worth it when you compare it to the cost of having a plumber open the wall to reposition the other pipe lower by 2 or 3 inches. This is the only other choice to the two ideas mentioned above.
You cannot rig a couple extra bends after the P trap to make its tailpiece go higher to meet the pipe in the wall.
(btw, the portion of pipe in question here is called the "trap arm" if you want to search with the right terms.)

    Bookmark   August 11, 2010 at 1:38PM
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Thanks for all the replies.

I live in a condominium, and the HOA board that is super slow at approving any type of work. I got the approval to change out my sink on the condition that no work would be done inside the wall. I've thought about calling a plumber to move the drain line, but I don't want to have to wait for HOA approval.

I lined everything up with the old P-trap, with the J-bend in reverse, and it does indeed fit. If water were to sit in the pop-up assembly, I can see how that could be a potential issue. Looking at the picture again, the actual ball (where the rod goes into the assembly housing) does appear to sit just above the center of the trap arm (thanks for the vocabulary lesson, davidrol!). Which makes me wonder if water will be trapped in the pop-up assembly housing.

I was talking to my colleague this morning, and he suggested that I remove my pop-up assembly. The hand press pop up is a great idea. I just found this one on Amazon that will match my faucet (brushed nickel):

If I decide to cut the existing tailpiece, wouldn't the stopper piece that goes up and down would be too long? (sorry, I don't know the technical term for that piece)

I found a photo of a reversed J-bend on a P-trap:

    Bookmark   August 11, 2010 at 2:10PM
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"I'm unable to visualize right now how a P trap can take less height when "reversed"."

I just re-read your post and just want to clarify that the only thing reversing the j-bend will accomplish is that it will allow everything to fit. It won't do anything to lower the actual trap arm or raise the pop-up assembly.


    Bookmark   August 11, 2010 at 2:14PM
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" ...stopper piece that goes up and down.. " Do you mean the 2 piece lever mechanism that moves behind the scenes to open and close the stopper inside the sink tailpiece ? That would not be too long, because you would cut it. (Easy to see in the first photo above that it is designed with holes at regular intervals, to enable it to be used at various lengths, shorter or longer). Note that the lever would be tossed into the garbage or long term storage if you install the hand press stopper. And that little hole in the back of the faucet base would become useless. Not a big deal.

Or, do you mean the actual pipe?
This too can be cut to any length as short as you like.
To cut it: a large pipe-cutter (5 seconds and a clean cut) or a hack saw (a minute or two, and use tape to mark a straight line around it first, and then take ten minutes to smooth out the rough edges left by the saw.)

    Bookmark   August 12, 2010 at 11:02PM
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The stopper piece I was referring to is the plunger. And after taking a look at it, I now realize the height is adjustable.

I went to several plumbing supply stores yesterday, and got the advice to just go ahead and use a reversed J bend, and monitor it for leaks. So despite such a configuration being not technically proper, I'm going to give that a shot.

I also saw several pop up and drain assembly sets that are shorter than the one I have. Mine's a Kohler, and from the flange to the hole in the back of the cast part of the pipe (for the ball and lever), it's a good 3/4 to 1 inch longer. Just for the heck of it, I installed my old pop up assembly, which is a Delta, and the housing for the ball/lever sits above the trap arm, but just barely. Still not high enough to allow the J bend to be installed the way it should be though. Instead of reversing the J bend, I might just might connect the J bend to the tail piece normally, and add a short extension piece from the other side of the J bend to the wall bend.

    Bookmark   August 13, 2010 at 4:47AM
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in your first post there are two photos. The second one shows the two long and small metal pieces that make the pop up thingie in the faucet base get connected to the other end that goes into the sink tailpiece.

One of these is a rod, and one is like a flat strip with holes in it.
You cut these two little metal pieces if they are so long that they get in the way of anything.
No harm done.
Common practice.
No need to ask permission.

Does this answer your question?
You said something about comparing the Kohler to the Delta to others...
"'s a good 3/4 to 1 inch longer..."
"...I also saw several pop up and drain assembly sets that are shorter than the one I have..."
What does all that mean? Does it mean you thought you were not permitted to cut these little metal pieces to fit the space available? Is this helping?

    Bookmark   August 13, 2010 at 3:05PM
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I don't think you can reverse a p-trap like that. While the nuts are reversible, the connections are a bit different. The end of the waste arm (horizontal piece) is flared, but the tailpiece (vertical part) doesn't have that. You'd be asking for trouble if it got accidentally knocked loose and not discovered.

    Bookmark   August 18, 2010 at 11:44AM
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I'm not concerned with the pop-up mechanism at all.

I was concerned with the pop up housing being level with the drain line. I was worried that if water stayed in the pop up housing, that the housing might be prone to leaks (at the point where the ball and rod go into the drain pipe).

I was also concerned with any code issues. I remember reading somewhere that there is a maximum allowable distance the p-trap can rise from the low point to the drain line. I assumed that reversing the j-bend would result in too much of a height difference to be code compliant (I'm still assuming this, since nobody has chimed in on this issue). However, more than the legality of it all, I really just wanted to know what bad consequences might happen as a result of reversing a j-bend.

Thanks for the SPAM. Not.

I was concerned about the connections. The waste arm has the flared tip, but it doesn't seem so different from the plastic washer thing that goes in the tailpiece.

I've went ahead and reversed the j-trap, and everything fits fine and feels really solid. I filled up the sink, drained it all at once, and there are no leaks. I've even opened up the pop up housing (where the ball goes in) and to my surprise, there is no standing water in there (the water line sits just below that).

I'll keep an eye on it to make sure nothing leaks. If it does, I'm sure we'll notice it right away, before there's any major damage. Aside from a few bottles of cleaning supplies, we don't really use the cabinet under the sink, so maybe I'll just leave an old aluminum lasagna pan down there. At least that way, it'll catch any leakage should any occur, and it will alert me to any leakage by amplifying the sound of any drips.

    Bookmark   August 18, 2010 at 6:00PM
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