Sink Drain Too High --- HELP !!

[Windsurfer]

My new granite kitchen top looks absolutely gorgeous except for one problem. The sink does not drain.

The new stainless steel 9" deep under mount double sink sit 3" lower than the sink that it replaces. Consequently, the drain out from the garbage disposal unit on the left sink has a height of 13.25" (when measured inside the cabinet) is lower than the drain stub which is 14" high. The right sink has its own drain pipe with stub at 18.5", also too high for that sink.

I was totally devastated to find about this problem as the installer had never mentioned or warned me about this when we decided on the sink.

After reading about similar situations in this forum, it is obvious I will have to lower the drain pipes.

By knocking out pieces of dry wall and skillful use of a camera, I found the 1 1/2" drain pipes went into the wall, turned left and around the corner for a total of about 5' to connect to a 2" vertical drain pipe. Below the two connections, I also found a third sanitary T coming from the laundry tub sink in the other direction (see picture, height is above subfloor). I have very limited knowledge on plumbing. Whatever help you can give is very much appreciated. Here are my questions

(1) It seems a logical thing to do is to move the three pipes together down by 3" (or more) as one unit. I will cut out 3" of the vertical drain pipe below the T fittings, adding back 3" of pipe above and reattach with a rubble coupling. And holes in the 2 by 4 studs where the pipes go through will be enlarged downward to lower them. Is that a reasonable approach?

(2) If I do (1), the laundry tub drain stub will be 10.5" or lower. Will that be too low ?

(3) While I am at it, I also want to add a downpipe for the washer. Not sure how to do that. It is ok to add a downpipe using another sanitary T above all the other ones?

(4) Any suggestions are welcome

Thanks a lot.

 

[Terry]

I think you meant, Sink drains too high. At least the drain from the wall is too high.

Sinks don't wet vent.
If your plumbing is as drawn, it's wrong.

Normally for a deep undermount sink, I rough the drain in at 16" from the floor.
You can connect both kitchen sink basins to the one drain.

The laundry sink should get it's own vent, even if you have to add an AAV to it.

 

[Sponsor]

 

[Windsurfer]

Thank you Terry, I've corrected the thread title to "Sink drain too high."
The sketch may not show it properly.
I will upload some photos shortly.
Please comment after seeing them.

 

[Windsurfer]

Pic 1 shows details under the sink. Here I have taken the garbage disposal out. The disposal when installed has an outlet 6.5" below the bottom of the sink.
Pic 2 shows the drain pipes going to the left and enter the wall between the kitchen and the laundry room.
Pic 3 is a shot of the laundry room showing the paths of the drain pipes entering into the vertical waste pipe. The vertical pipe go down to the basement to a larger drain pipe connected to the main drain.
Pic 4 shows a close up of the 3 sanitary Tee's connecting to the 2" vertical waste pipe.
Pic 5 looks straight down at the vertical 2" pipe
Pic 6 looking up ... not sure how it ends

 

[CountryBumkin]

If you use the drain pipe for the "left" sink (the lower pipe) for both sinks will that get you low enough?
You don't need separate drain line for both sinks, they can share one p-trap.

 

[Plumber69]

I could make this work with this setup. Appears to me that the top pipe is a vent pipe done wrong. U could use it as a vent pipe but u would need cleanouts on it.

 

[Reach4]

You are probably going to want to combine the kitchen drains as Terry suggested. But you could have separate if you wanted by adding the C-D vent.

For the laundry sink, you will split off the vent at A, and it will join the trap arm at B. You will not use a sanitary tee at B, D, E, or F. I am not sure what fittings those should be. Not sure what would be best at C or A.

 

[Plumber69]

There's so many options now it's hard for plumbers to guess hieghts and exact locations of supplys and drains. Unless they have it there or the specs.

 

[Windsurfer]

Thank you all for posting.
CountryBumkin: The lower left sink drain pipe is still 3" too high.
Plumber69: Bad builder I guess, if the upper pipe was meant to be a vent. But it lines up perfectly with the right sink drain hole and was connected OK to the sink before I took it apart. Please see the attached pic for more details on the stack fittings and show me some other options.
Reach4: Yes, I would combine the two drains at the sink as Terry suggested. The vent split you suggested, what is the main purpose ? I would still have to drop the lines by at least 3"
All: My main concern is the laundry sink drain. Right now it is 13.5" off the sub floor level and crosses right on top of the water line outs. If I drop all 3 tee's together by 3", I will have to reroute the water lines. And the sink drain stub will be only 10.5". I think it is going to be too low. So I am wondering if I can keep the stub height the same but lower the San-T end by 3". This will result in a much steeper run slope than 1/4" per foot. Is that going to be OK ? Splitting the vent as Reach4 suggested will help doing that ?
An alternative is to swap the order of the tee's. Relocate the laundry sink drain tee to above the kitchen sink drain tee. But it that going to create a problem ? There is going to be a lot of water from the washer emptying quickly into it.

 

[Windsurfer]

CountryBumkin: I should clarify that the garbage disposal was mounted on the left sink before I removed it. The regular drain tail pipe from the right sink was taken out and install on the left sink as you see in the pic. Sorry for the confusion.

 

[Reach4]

That top fitting is a sanitary tee, and it is vented fine.
The lower two need vents off camera. Are you sure they are not there? Because if somebody was cheating, they would have made those lower two fittings be sanitary tees. It still would not have been permitted, but it would have typically worked. So I suspect there are vent pipes that are hidden.

The vent split you suggested, what is the main purpose ? I would still have to drop the lines by at least 3"

Because it is a rule. The rules are mostly based on principles that I think don't want the venting to be blocked when something clogs.

 

[Windsurfer]

I am 100% sure the middle drain is not vented as the dry wall is complete off around it and I don't see any pipe that go up from it.
The lowest one I am not sure.
Can you please also comment on the laundry drain ? Is it ok to have a slope > 1/4" per foot. I am very confused whether 1/4" is a minimum or maximum.

That top fitting is a sanitary tee, and it is vented fine.
The lower two need vents off camera. Are you sure they are not there? Because if somebody was cheating, they would have made those lower two fittings be sanitary tees. It still would not have been permitted, but it would have typically worked. So I suspect there are vent pipes that are hidden.
Because it is a rule. The rules are mostly based on principles that I think don't want the venting to be blocked when something clogs.

 

[Reach4]

Can you please also comment on the laundry drain ? Is it ok to have a slope > 1/4" per foot. I am very confused whether 1/4" is a minimum or maximum.

It is a target until the vent. That is because the pipe passes both air and water. After the vent, 1/4" becomes a minimum.

 

[Windsurfer]

Does that mean I can increase the slope of the laundry pipe ? The span of the pipe is 5' and the drop is currently 2".
Will there be any problem if I increase the drop to 5" with the same span ?

 

[Reach4]

If you add a vent, you can increase the slope after the vent.

 

[Windsurfer]

From what you're saying, after the vent is the length between the vent and the vertical pipe, right ?
So if I add the A-B vent (in your pic) to the horizontal drain pipe somewhere between the tee and the stub at the sink, I can put a steep drop after the vent ? Is there a limitation where you can put the vent ?

 

[Reach4]

From what you're saying, after the vent is the length between the vent and the vertical pipe, right ?
So if I add the A-B vent (in your pic) to the horizontal drain pipe somewhere between the tee and the stub at the sink, I can put a steep drop after the vent ? Is there a limitation where you can put the vent ?

At least two pipe diameters after the P-trap. With 2 inch pipe, you would want 4 inches. This install should have a little more:

There are 22.5 degree and 45 degree elbows readily available.

 

[Windsurfer]

Thanks .. I will sketch out a plan and post it.

 

[Windsurfer]

This is what I am thinking. I will combine the left and right kitchen sink drain into one and lower by 3".
Add a re-vent and keep the current height of the laundry sink drain.
I am not sure about how high the re-vent loop has to be, and if the heights of the drains entering the stack are okay.

 

[Reach4]

https://terrylove.com/forums/index.php?threads/laundry-trap-arm-too-long-can-i-revent.55374/
42 inches above the floor and 6 inches above the highest sink/standpipe flood level.