Roughing in kitchen sink

We are remodeling our kitchen and are installing a double kitchen sink under a 4' wide window. We would like to have separate P traps...one for the sink and one for the disposer....and each going into their own drain arms.
I have re-framed the exterior wall on that side with 2x6 studs to accomodate 1 1/12" ABS pipe running horizontally in this new kitchen wall for about 7 feet and then turning into the garage and along the wall were it will tie into the 1 1/2" washer drain, which is 1 /12". I will bore the pipe holes as close as possible to the sheathing side of the studs, to leave as much of the stud intact as possible...and I will protect the pipe with 1/8" x 5" steel plate under the sheathing along that pipe run. So accidentally nailing into the pipe is not an issue.
But, I need to run 1 1/2" - so I am really confused by all the options you present for a double sink drain. I'd like to use the layout you show in your double bathroom sink new construction....but use the double sanitary tee in all 1 1/2 with the sink arms on each side, the vent out the top and elbowing to the right and then up the side of the window framing and out the roof. And the drain going down and connected to a long sweeping el connecting to the horizontal pipe with normal .25"/ft drop. i could put a sanitary t under the double ST and face it out so there would be an exterior cleanout access. What to you think??
Do you see any problems....

runswithscissors said:

What to you think??
Do you see any problems....

Click to expand...

I can't see anything. No picture provided. With that much info a picture would go a long long way.

Thanks for the quick reply.... Just caught nasty cold last night...so I'll try to mock something up today.

But just in case I can't it would basically look like the New construction photo above. Except:

1. I would bring the arms in closer to the double fixture cross - to align with the Kitchen Sink drains.

2. The vent would come off the top of the double fixture cross and go up a foot or so to about 6" under the window sill plate - then go to the right about 2' and then up and out the roof.

3. I'd put a clean-out in the vent pipe, just above the double fixture cross....facing out=for exterior access.

4. The horizontal drain pipe would connect to the bottom of the double fixture cross and would sweep left.

Everything in 1 1/2" ABS including all 4 openings of the double sanitary T - If I can find one in that configuration.

Here is a picture of the double kitchen sink on a temp stand. Disposer will go on right, and we think that having 2 P-Traps going into their own drain arms would be best. To keep things clear, and to free up under counter space. (plus it might just be code out here now...we don't know)

Are we on track so far?

Ok, here is the pic showing what we think will work and meet code...based on my previous detailed posting and on Terry's "New Construction" picture in the thread above. I would prefer to use 1 1/2" ABS for EVERYTHING....so that I can keep the 2x6 studs as thick as possible....BUT if you professionals think that 1 1/2' is asking for trouble...both from a drainage and code point of view...I'll use 2". As mentioned in my previous post...I'd bore the holes on the exterior side of the stud and protect with 1/8" steel plate.

I thank everyone for their input.

A kitchen sink waste is 2.0"
The trap arms can be 1.5"
The vent can be 1.5"

A washer drain and standpipe need to be 2.0"
The vent for a washer can be 1.5"

Many times if the home is old, you may find 1.5" dropping into a cast iron hub that will take a 2.0" pipe.

If you are installing two fixtures with one vent, that would use a double fixture cross.
Not a double sanitary cross.

Here is another pic...showing the vent better

Yup...our house is a 1963 tract home built just before ABS was the thing to use. And YES, where I intend to tie this new kitchen waste drain to...is at the washer drain standpipe. And it is 3" CI with a 1 1/2" gal. pipe leaded in. Guess I'll have to remove the gal. pipe...clean out the lead and oakum and somehow connect the new 2" ABS inside.
Only the hub of the CI pipe is exposed at concrete level...so no chance of cutting it. Also I don't have clearance for one of those rubber bell shaped adapters...if they are permitted to be used. What do you think about pounding in oakum and lead wool around the new ABS??

You can drill out the lead and use a rubber insert inside the hub.



Except you would pick up the one for 3" pipe.

OK...great.

And is this the Double Fixture Cross ? At Home Depot, they call it this: NIBCO 2 in. x 1-1/2 in. x 1-1/2 in. ABS DWV All-Hub Double Fixture Sanitary Tee Here is a picture of it from their website:


Is that the right one?

So...after all your great advice, I will make the drain line 2"...boring the holes thru all the timber you see in my picture...on the farthest outside edge. That will leave me nearly a full 3" of wood left on the inside...which I would guess is plenty. If you look at my pictures, you will see that there are plenty of studs, jacks and trimmers on/under each side of the window...in that short 7' wall run...what say you.??

Lastly...because I now need to bore thru all that timber...and I used plenty of nails to sandwich things together......what sort of boring device do you recommend. (I am sure I am going to hit a few nails) I have read that notching is not up to code...but with the 3" left, and the steel plate..it sure would be easier. I'd rather bore the holes if there is a good tool.

Again thanks for ALL your help.!!!!!!!!!!!!

Make sure that horizontal part of the vent under the window is at least 42" above the floor or 6" above the flood level rim of the sink. If that wall is load bearing and it's 2 x 6 construction you can not drill them for 2" pipe without doubling every one that you drill.

What do you mean "IF" they're load bearing. When have you seen a non-load bearing wall like that?

I'm not sure why you need 2 traps... never seen that before.

I would rather see the whole thing in that stud bay to the right of the window, and a longer trap arm personally.

runswithscissors said:

I will bore the pipe holes as close as possible to the sheathing side of the studs, to leave as much of the stud intact as possible...and I will protect the pipe with 1/8" x 5" steel plate under the sheathing along that pipe run. So accidentally nailing into the pipe is not an issue.

Click to expand...

Are you crazy? When have you ever seen a hole drilled anywhere but the middle of a stud for this purpose?

You put all of that new framing in, and now you plan to chop it up

Why does the drain need to go horizontally just below the cross-fitting?

Whoa....hold on. Don't beat me up too bad. For starters, it WAS a 2x4 wall holding the roof over a small portion of the kitchen. I removed the old single pane garden window there and removed all the exterior stucco....and then removed all the old 2x4 studs...AND then built a NEW wall using 2x6's complete with a 2x6 mud sill. I installed this new wall on top of the old mudsill...flush on the inside. The extra width hangs off the exterior side bearjng no weight.
I did this so that I could bore holes for the drain pipe at the very outside edge of the 2x6's....and barely cut into the original 2x4 load bearing cross-section. The load is held by the inner portion of the untouched 2x6.
As I mentioned in my previous post...I will nail a 1/8" x 5" x 7' plate of steel along the drain run...to protect it...then sheath and stucco the outside.
I will plate any other areas where the pipe is closer than 1".

The old drain is under the slab and is getting finiky...so am routing this sink to a better drain and so the new drain needs to go left and tie into the 3" CI pipe in the garage.

This is going to look very handyman special...

Yes,...we had a "one butt" kitchen with an island separating it from dining room. We removed the island, and now have a huge open space. We are putting the kitchen where the dining room was. So the sink gets moved 15 feet left to where you see it...and we didn't want to run the drain thru the inside of the back of our new cabinets...and had no room in the design to space them away from the wall.... Can't go to the right to the old drain because new wall pantry is in the way. So what you see, and I describe, is my attempt to keep the structural integrity...and head the drain to a place closer to the sewer main.

Oh, and the reason I thought two trap arms would be good is: "Disposer will go on right, and we think that having 2 P-Traps going into their own drain arms would be best. To keep things clear, and to free up under counter space. (plus it might just be code out here now...we don't know)"

I should have started out by saying that we are swapping rooms. We are moving kitchen to where the dining room was and vice versa. We cut away the peninsula that separated our "one butt" kitchen from the adjoining dining room. That left an open room for both. The sink is now to the left about 15 feet from where it was. New cabinets will run along that wall in both directions.

Can't plumb back to OLD sink drain because new wall pantry will be in the way..and the old CI drain under the slab was getting finicky. Anyone that has jack-hammered up their floor in our neighborhoods out here have had them crack in short order...due to the soil, earthquakes etc etc...no matter who did the work. So best route was to the 3" CI washer drain in the garage. (the original KS drain angled under the slab an over to it anyway...and the garage drain is less than 25 feet to the sewer main to the street)

Also, we didn't have the room in the design to space the cabinets out away from that wall as a door was in the way AND we didn't want to punch holes in the sides of our new cabinets to run the drain along the inside back of them. So, I thought that what I described above would keep the structural integrity, hide the pipe and solve the problem. I don't mind doubling up on the 2x6's as Tom suggests...

As far as why the two trap arms for the kitchen sink - here was my reasoning: Large sink basin on left and Disposer on right, each having their own P-Trap going into their own their own separate drain arms might eliminate the disposer pumping into the other sink...as our old one would do. And without the crossover between the disposer and sink p-trap, it would free up under counter space.
(plus it might just be code out here now...does anyone know)

Well, I am sure I have set myself up for some pretty serious ridicule here....but I don't have many alternatives...work with me here please !!!

The only times I install "multiple" drains for a sink is when I know it will be a three compartment sink and the extra one will make connecting the drains easier. Otherwise there is very little, if any, benefit by putting in two drains, and it complicates the installation doing so. You will have to run 2" to do it, (and it would be a better idea in any case), because there are no "all" 1 1/2" double fixture fittings.

Thanks HJ....I will take your advice!!! So now what would you do?? Looking at the pic, I can only go left with the drain. I can put the vent straight up and elbow it right or left...I have the 42" by an inch. Or I could go straight to the right from the sink arm and up that narrow bay....or I could put it on the drain pipe to the left and straight up the bay to the left of the window...I know that would give me a wet or dirty arm...but the distance would be just over 3 feet. (from the pic, you can't see the studs on the left...but the outside wall sheathing is only tacked on and can easily be exposed so I can bore holes and put things where they ought to go.

Also, if you were doing it, could you describe or sketch your lay out...what fittings would you use...and where would you locate the vent and "clean-out" - there is nothing on the outside wall - so the clean-out could go anywhere??

I am adding this to my previous post to see if someone can let me know if I can/should do it this way. Here is a picture that dlarrivee posted in another "TL" thread called "A few code questions" ...
This is what I tried to explain that wanted to do for the new install of our double kitchen sink with disposer. I thought that having two trap arms would be good for two reasons..one to free up some under sink space and second, to have separate p-traps - one for the big sink side and the other for the disposer side. (if it is ever determined that it is against code, I could always cap one)
Of course, I would have to shorten both trap arms to basically fit into one stud bay. A double fixture fitting with two long 90's will fit...AND I would put a san tee just above the double fixture fiitting for a clean-out, accessible from the outside.
Also, if you go back to the pic I previously posted...I would be running a 2" waste drain pipe about the same height as you see in this picture, but I would be going about 20 feet further to the left to a 3" CI drain in our garage.

I would use 1 1/2 for the vent up the 42" over to the right to the stud bay past the window and up thru the roof.
Would someone please clarify that the 42" is an O.C. measurement...thanks

Here is the pic dlarrivee posted:


I have both sides of the wall opened up...so I want to get it right before I sheath and stucco.
I thank Everyone for all your help