Triple bowl sink drain plumbing

Jwray · Oct 26, 2004

I purchased a triple bowl, cast iron sink for my kitchen remodel. The bowl configuration is as follows: large, deep bowl on left; small (narrow), shallow bowl in center; large, deep bowl on right. It's the pretty standard 3 bowl configuration designed for a garbage disposal in the center bowl.

I plan to install the sink with a garbage disposal in the center and in conjunction with a dishwasher.

Here's the question. How does one plumb the 3 drains, dishwasher, trap, trap arm, etc. into the DWV stub out?

Is there a pre-packaged "kit" available for this setup similar to what you commonly see available for a 2 bowl sink? I haven't had any luck at the standard Big Box stores (L's & H.D.) in my area.

Thanks for the help.

Joel

BTW if anyone has any suggestions for getting this thing in place let me know. Did I mention it was CAST IRON. It took 2 guys really working just to get it into the house.

hj · Oct 26, 2004

sink

There is no "good and easy" way to plumb that configuration. There is also no prepackaged setup. The disposer in the middle means that the one sink drain has to go around it. If you know that it will be installed ahead of time, then you can put in a second drain opening for that sink. But, in your case you did not have that luxury. If possible, install a "Y" between the trap and the wall and extend a separate line to the "odd" sink bowl and hook up the other one and the disposer if it were just a double sink. If you do not have that much room, then you are destined to buy alot of slip fittings and tubing and create a "kludge" which jogs around the disposer and connects all three sinks to one trap. In any case it is seldom an elegant looking drain system. If you think yours was heavy, you should try lifting mine. 48" wide with 8" deep bowls.

Sponsor · 2022-01-29T12:20:58-0800

Jwray · Oct 26, 2004

Clarification on suggestion

HJ,

Thanks for your advice. I guess I've been on a bit of a snipe hunt and just needed to apply some ingenuity.

Let me explain my situation a bit further and make sure I completely understand your suggestion.

I am in a complete remodel situation where the walls are bare to the studs and the plumbing is being redone, so I have some flexibility. Also, the kitchen is over an unfinished basement, so I have some lattitude in where the drain pipes go.

If I read your advice correctly you would prefer the 2 drain scenario, i.e. plumb the center bowl/garbage disposal/dishwasher + one of the large bowls like a standard 2 bowl sink to its own trap and drain and then plumb the remaining large bowl like a single bowl sink to its own trap and drain. Am I correct in my understanding?

If so, I have a couple of questions about the 2 drains.

1. I would just drop the 2 drains into the basement and connect up to a properly sloped horizontal run heading toward the main building drain, correct? I'm in an outside wall which will not allow me to drop straight down to connect to the horizontal run (interference with the rim joist, foundation, etc.). Is it OK to use some combination of bend fittings (say 1/8 or 1/16 bends) and pipe stubs to come away from the foundation at an angle and then go vertical again to hit the branch of a combo wye in the horizontal run? Probably a good idea to put a cleanout in the upper end of the highest wye as well?

2. The sink is under a double window (of course) which is in the way of the ideal, vertical vent. I believe this means I have to come up vertically as high as I can above the flood rim of the sink and then head horizontal (with proper slope upwards) until clear of the window and then turn vertical up to the roof as soon as possible.

Can I run both of the vents, from the tops of the drain sanitary T's, vertically into the horizontal run? I would connect to the lower end of the horizontal vent line with a vent el and the middle of the horizontal run with a combo wye. The horizontal run would then continue until clear of the window and connect to the vertical line to the roof via another vent el.

3. My only other concern is I'm not sure I can squeeze the dishwasher drain line into the garbage disposal port with it up under that middle sink. It's kind of tight in there. If this is the case would you suggest plugging the garbage disposal dishwasher port and using a sink drain assembly with the dishwasher port? Those flexible dishwaser hoses and drain port connections have always seemed so cheap looking to me, i.e. a leak waiting to happen. Is there a better way to do it or am I being over concerned?

I hope that is clear.

Thanks again for the advice.

Joel

Jwray · Nov 1, 2004

For HJ - follow up ? to triple bowl sink answer

HJ,

I think this must have slipped through the cracks. I also sent you a private message about this, but I know those don't always catch your eye as I have overlooked them myself on other forums.

What's the best way to go back and forth with someone in a thread without falling off the radar screen?

Your input on my follow up post quoted below would be greatly appreciated.

Thanks,
Joel

jwray said:
HJ,

Thanks for your advice. I guess I've been on a bit of a snipe hunt and just needed to apply some ingenuity.

Let me explain my situation a bit further and make sure I completely understand your suggestion.

I am in a complete remodel situation where the walls are bare to the studs and the plumbing is being redone, so I have some flexibility. Also, the kitchen is over an unfinished basement, so I have some lattitude in where the drain pipes go.

If I read your advice correctly you would prefer the 2 drain scenario, i.e. plumb the center bowl/garbage disposal/dishwasher + one of the large bowls like a standard 2 bowl sink to its own trap and drain and then plumb the remaining large bowl like a single bowl sink to its own trap and drain. Am I correct in my understanding?

If so, I have a couple of questions about the 2 drains.

1. I would just drop the 2 drains into the basement and connect up to a properly sloped horizontal run heading toward the main building drain, correct? I'm in an outside wall which will not allow me to drop straight down to connect to the horizontal run (interference with the rim joist, foundation, etc.). Is it OK to use some combination of bend fittings (say 1/8 or 1/16 bends) and pipe stubs to come away from the foundation at an angle and then go vertical again to hit the branch of a combo wye in the horizontal run? Probably a good idea to put a cleanout in the upper end of the highest wye as well?

2. The sink is under a double window (of course) which is in the way of the ideal, vertical vent. I believe this means I have to come up vertically as high as I can above the flood rim of the sink and then head horizontal (with proper slope upwards) until clear of the window and then turn vertical up to the roof as soon as possible.

Can I run both of the vents, from the tops of the drain sanitary T's, vertically into the horizontal run? I would connect to the lower end of the horizontal vent line with a vent el and the middle of the horizontal run with a combo wye. The horizontal run would then continue until clear of the window and connect to the vertical line to the roof via another vent el.

3. My only other concern is I'm not sure I can squeeze the dishwasher drain line into the garbage disposal port with it up under that middle sink. It's kind of tight in there. If this is the case would you suggest plugging the garbage disposal dishwasher port and using a sink drain assembly with the dishwasher port? Those flexible dishwaser hoses and drain port connections have always seemed so cheap looking to me, i.e. a leak waiting to happen. Is there a better way to do it or am I being over concerned?

I hope that is clear.

Thanks again for the advice.

Joel

hj · Nov 1, 2004

drain

You changed the whole scenario when you indicated that the walls are still open. In that case I would install 3 drains, one for each sink, and then the disposer can be rotated so that the dishwasher port is not against either sink. I would install the two outside drains as "dirty arms" to the vertical pipe, and then install a tee above that fitting for the disposer. Its opening is higher so the elevated tee is usually just at the proper elevatin. This way you do not have to worry about any additional vents, of course this assumes that the vertical pipe is between the two sinks, otherwise it takes a little bit more piping to accomplish this.

Jwray · Nov 2, 2004

Let me make sure I understand that configuration

HJ,

Thanks for the follow up. Sorry I didn't mention the open walls originally. I agree that is significant.

I had to spend some time "visualizing" your description in my mind before I got it. Let me make sure I'm clear on it.

Install a vertical drain/vent line in the wall and vent around the window as I described in my earlier post. In that verical drain/vent line install a sanitary cross with a sanitary T stacked on top of it. This is just like any other sink drain setup except for the 2 stacked fittings.

From the sanitary cross branches run 2 (1 to each side) properly sloped horizontal lines inside the wall and terminate with a drain el coming out of the wall with the opening in line with the side sink bowls. These horizontal lines would be the "dirty arms" you referred to? Is a "dirty arm" the same as a wet vent?

The 2 side sink bowl tail pieces would each connect to their own P traps, a trap arm, and then into the drain el connected to the "dirty arm".

For the center bowl I come out of the garbage disposal drain outlet, into a P trap and into the sanitary T branch. I also install the standard corrogated plastic dishwasher drain line into the garbage disposal port and mount the disposal rotated so that all this lines up nicely.

Is this all correct? Did I get it?

Thanks for hanging in there with me. That third bowl adds a bit more complexity than I thought.

Thanks,
Joel

hj · Nov 2, 2004

drain

It looks like you have got it. The best configuration is if the vertical pipe is approximately centered on the sink but a little way in either direction is no problem since the disposer and trap can be rotated to give considerable leeway.

Triple bowl sink drain plumbing

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