sink drain exterior wall

iskyfly · 11-02-2011, 07:00 PM

The first image is the sink base cabinet. The composite image below it is in the basement looking up.

So I had new cabinets and new countertops and had a deeper sink installed.
Nobody, including myself, thought to consider the location of the drain pipe. With the new sink the discharge tube of the garbage disposal is now lower than than the drain pipe coming out of the wall.

The wall is an exterior wall with a window above the sink. The drain pipe runs horizontally 3ft across to the right.
In the composite image below the cabinet image you can see on the right side where the pipe comes down and then runs overhead towards the center of the house where it connects to the main drains.

Opening up the wall means cutting into the back of two cabinets. Instead of doing that, I was wondering if I can drill straight down in the rear right side of the sink cabinet and 90 to the right, run a horizontal piece and join up to the existing drain pipe and cap off old pipe in the cabinet? All bathrooms are in the center of the house.

The kitchen sink is the only drain pipe located against an exterior wall. I went on to the roof and noticed one vent stack just before the apex of the roof. I went in the attic and I see that stack coming up out of the center of 2nd floor ceiling. Considering that there is only one vent stack on the roof, how likely is it that the sink drain does not have a vent stack of its own or is it connected to the vent stack in between floors? Thank you!

ben's plumbing · 11-02-2011, 09:01 PM

yes you can do what you are saying as long as you keep the pipe in wall behind cabinet in system because it should be a vent for kitchen sink???? as a side thougth the pipe comming out of wall could be used for auto vent if code in your state permits it..ben

iskyfly · 11-03-2011, 07:26 PM

Thank you Ben.

How do I go from a 1.5 inch p-trap w union to the new 2 inch vertical pipe that I put in the rear right hand side of the cabinet? Is there such a thing as a 1.5 to 2inch 90 elbow? Or do I need to go about this differently?

Thank you.

ben's plumbing · 11-03-2011, 07:32 PM

not sure why your saying 2" the pipe under the sink base in basement looks like 1 1/2 pvc ?...after you run new pipe through cabinet you will need 1 1/2 desanko fitting and.......then reinstall p trap..... a desanko fitting will glue on pvc pipe and have threads on other side for trap end.......

**oh'mike** · 11-03-2011, 07:38 PM

If the drain pipe is 2" --and the new vent will be 1 1/2"---use a 2"-1 1/2" -1 1/2" T--

If no vent exists see if an AAV (air admittance valve) (or 'cheater vent') is acceptable in your area.

iskyfly · 11-03-2011, 07:52 PM

pipe in basement is 2".

ben's plumbing · 11-03-2011, 08:08 PM

thanks for the new picture..your right pipe is 2" now as mike said you can use a 2 x 1 1/2x 1 1/2 tee auto vent off top disposal disposal drain into branch your done.....ben they do make bushings and reducers from 2-11/2.....

iskyfly · 11-03-2011, 08:10 PM

thank you both.

**oh'mike** · 11-03-2011, 08:12 PM

I added some spaces to your original post---

To do this properly you should open the back of the cabinet and do the surgery there--here is why.

If you simply cap the old opening and add a T below the floor--move the pipe over a bit and then go up -- you will be creating an S trap ---not code--but more importantly ----the trap may be self siphoning ----allowing sewer gas int the kitchen.

Open the back of the cabinet---use a multi-tool if you have one (they are dandy in a tight spot like that---

Once it's opened and the drywall removed the change is fairly straight forward..--Mike--

ben's plumbing · 11-03-2011, 08:56 PM

thanks mike I got the impression he was not going to use s trap....after comming up through base he was going to reinstall p trap .....I also thougth he going to cap existing outlet... because he did not want to cut back of cabinets?????? did I miss something......

**oh'mike** · 11-04-2011, 08:32 AM

He will be creating an S trap with the pipe --combined with the P trap.

If he added a vent into the riser at the top it would work---but to hook the vent into the house the back of the cabinet would need to be opened--(or an AAV)

Every one---take a lesson here----when redoing a kitchen---lower that drain height-

New kitchens often get--An undermount sink--a deep sink--and a garbage disposer--all will add to the need for a lower drain.

Also the new sinks have the drain holes further back---so the old drain piping will no longer line up with your needs----

mystic_cobra · 02-04-2012, 07:38 PM

I have the same issue...

Kitchen renovation, deeper sink. Drain pipe height is 18" above finished floor and nearly directly in line with the exhaust from the disposal.

My thread with pics.... kitchen sink disposal drain trap problem

Can I connect a series of pipes to fix this and have it pass code without opening the wall to lower the drain pipe?
thx