Home>Discussions>PLUMBING>2 P-Traps on a kitchen sink - any unforseen issues?
4 posts / 0 new
Last post
2 P-Traps on a kitchen sink - any unforseen issues?

In a rental I am working on, I have switched out a kitchen sink. I'm going from a standard double bowl to a large/small bowl configuration. I have run into an issue getting the drain pipe spacing to work with the new sink drain locations. I want to avoid moving the 1-1/2" PVC coming through the wall.

Because of where the drain comes though the wall, the only solution I have working so far is to have a P-trap coming off the small bowl before the center T and a P-trap after the center T before going to the stub coming through the wall. The large bowl has a straight pipe to the T and there is not enough room for a P-trap there. I have not been able to find a straight section of thin wall long enough to get me from the small bowl to the T.

So, thinking like a drop of water in this sink.... From the small bowl it goes down the drain, thru a P-trap to the T and thru a second P-trap before hitting the drain stub. From the large bowl it goes down the drain, thru the straight pipe to the T then thru the P-trap to the drain stub.

Any issues with having 2 P-traps like this on the small bowl? It has been working for about a week now as I looked for a long enough straight section.

Re: 2 P-Traps on a kitchen sink - any unforeseen issues?

Instead of using the thin wall piping you can use regular PVC. If you are shopping at the big box stores go to the aisle where they have all the PVC elbows and stuff. You will be able to find traps, couplings, etc. so you can hook it up the way it is supposed to be. This will allow you to use a piece of PVC long enough to reach the T from the small bowl. Hope this helps you out.

Re: 2 P-Traps on a kitchen sink - any unforseen issues?

bp .... if I'm reading this correctly you have a double trap drain ( in series ) setup? .... maybe a picture ?

The problem with a double trapped setup is if a large volume of water is released down the drain it may carry with it enough pressure or velocity to pull the water right out of the traps...and you know what that means.....sewer gases ..... also the second trap tends to clog up.

I'm pretty sure it's a code violation since the IRC and UPC do not allow a double trap ( in series) but you can do a separate trap on each sink ( in parallel ) joined together in an appropriate wye to the wall.

Re: 2 P-Traps on a kitchen sink - any unforseen issues?

Yep, they are in series from the small bowl, although there is a "vent" between them (the drain pipe to the large bowl) so siphoning hasn't happened. (there is also the normal vent in the wall after the trap) I figured it was not up to code, but it was all I could cobble together with the pieces I had on hand at the time and I needed to get it hooked back up. Either I will have to go with the wye set up with the two thin wall traps, or I will use the regular PVC (trap included) to the tailpieces. I'm probably going with the second solution.

I have been looking and asking at a couple plumbing supply places and have not found a thin wall 90 with the threads at the tailpiece connection that gives me the extra 1-1/2" I need to get to the T.

Thanks for the input.

Sponsored Stories

TV Listings

Find TV listings for This Old House and Ask This Old House in your area.