Forum Title: Getting rid of an s-trap under my un-vented kitchen sink?
Looking for some help re-doing the drain under my kitchen sink before I install a new sink and faucet. My house is a single story ranch with a full unfinished basement with one plumbing vent located at the top of the sewer stack running to the roof in the wall between the bathroom and kitchen. The kitchen sink is located 6 feet from that common wall and is on an exterior wall. The original drain exited the cabinet through the floor and the last home owner has an s trap set up before the drain exits thought the floor of the cabinet. There is no vent connection in the sink cabinet. In the attached jpg I've sketched out the situation crudely with what I think is the correct solution. If I'm on the right track, is there any way of redoing the drain in an efficient manner in order to be able to fit as much in the cabinet as possible? Like a trash can on one side? One thing to note. The current sink has drains that are centered in the basins and I would like to use a sink that has the drains near the rear of the basins. Doing so would put the left basin drain almost exactly over the drain pipe in the bottom of the cabinet, which is why I though it was best to locate the trap under the right basin. I've never used an air admittance valve before, and I'm not sure where to find out if they're legal in the Syracuse NY area. If it is ok in my area, am I allowed to branch horizontal before going vertical with the AAV? How much higher than the p-trap does it need to be? Connecting a vent through the wall to the main vent stack would entail a full kitchen remodel. I'm assuming that the original drain exited through the bottom of the cabinet because the sink is on an outside wall and the original builder from 1957 didn't want freeze issues. Currently the right basin drains very slowly if the left basin is plugged and full of water. It drains fine as long as the left basin is empty or draining water at the same time. I'm I on the right track? If so, would it be advisable to create this drain system with cemented 1.5 inch pvc pipe with a couple of cleanouts (P-trap and t-junction at base of cabinet) up until the point of the p-trap and then use the threaded slip joint pipping from the p-trap to the bottom of the basin's? Thanks in advance.
Category: Plumber Post By: BRITTANY BATES (Albany, GA), 05/20/2017

Thank you Macgyver, The existing pipe into the cabinet is a 2 inch pipe with a 1 1/2 slip joint connector on top of it. I appreciate the tip of using a wye as soon as possible to get all the plumbing to the side and back as soon as possible, especially going with a new sink with the basin drains near the rear! I knew I came to the right place to ask my question!

- KELLY BELL (Redmond, WA), 09/06/2017

Macgyver, I just wanted to stop back and say thank you for your earlier help! I've attached a photo to show you how well your advice worked out. It may not look it, but where the bottom of the AAV valve screws in the the coupling is 2 inches above the bottom of the sink basin. I could have ended up getting that higher but wanted to be able to reach in with my warn out shoulder to change it down the road. I'm not a professional by any means, and I know you pro's on the site will immediately pick up on the point where I was day dreaming as I was gluing the pvc together! Lol! Thanks again!

- THEODORE SIMS (Coon Rapids, MN), 09/15/2017

aav/cabinet preferably, use 2'' not 1 1/2'' pvc from th floor up. code is 1 1/2 only for a lav . then as you suggested, 1 1/2'' slip joint after the tee, using a sj ptrap and continuous waste tip on the cabinet floor. after you cut it out,,install the wye, then cut a piece of sheet metal to use as an escutcheon

- JON REID (Rancho Cucamonga, CA), 09/26/2017

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