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I already know that I will hire a plumber to perform this swap/install-- what I'm looking for is feasibility or hidden "gotchas" with the idea before I commit to buying the sink.

What I have is a standard (so I believe) 22x33 dual basin sink, as pictured below (above the sink and in the cabinet below.) Note that the dual basin sink, as one would expect, has two drains. One of them (left) is attached to a garbage disposal. Mostly unseen, to the right, is a dishwasher that gets hooked up to the thing.

What I want is a 22x33 single basin sink similar to (or perhaps exactly) the one pictured here.

Specific things I am concerned about:

  • Going from dual drain to single drain, where the new drain location does not match either of the old ones
  • Above, especially in the presence of the garbage disposal
  • The hookup to the dishwasher

I'm not asking how to do any of those things, per se, only whether a competent, licensed plumber will be able to get things installed and working together correctly.

And also:

  • Am I putting the horse before the cart? Meaning, my plan is to buy sink then contract plumber. Should I be doing that in the other order, contracting the plumber and vetting the hardware prior to purchase?

Assume, if it was not already obvious, that I know nothing about plumbing.

PS - I hate that sink. It was here when I bought the house.

Sink above and below-- updated

Angled view:

Angled view Label on sink:

Label on sink

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  • 1
    Plumbing looks good, but what's your plan for the counter cutout? (Or is the old sink and new sink miraculously the same size?) Nov 27, 2022 at 23:43
  • @AloysiusDefenestrate I had the wrong image in, sorry. I've updated it to show the above view as well. I measured the existing sink as 33" by 22" myself from where the raised part begins and ends. All of the sinks I am considering are listed as 33" by 22" for exactly that reason. Is that sufficient, or is there additional work/measurements I need to take?
    – Reader
    Nov 27, 2022 at 23:53
  • Perfect world, you'd be able to measure the cutout in the counter to see that it matches the spec in the amazon listing (Template Size: 32.2x21.2 inch). As long as the cabinet is about 36" wide, the swap should work fine. You might consider a new faucet at the same time if the existing one is aging or you have hard water. Nov 28, 2022 at 3:55
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    Careful of the corner radius - I tried to replace a damaged sink with one a few mm larger, expecting worst case to have to enlarge the cutout. But the original had almost sharp corners, and the new one very rounded corners, which weren't specified or visible in the picture. Despite being larger it still had gaps on all the corners. Luckily I managed to return it.
    – Chris H
    Nov 28, 2022 at 10:00

4 Answers 4

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Any competent plumber can make the transition from the double sink in the pic to a single sink.
The garbage disposal (it's not a compactor) will be attached to the single drain and your dishwasher can be hooked up to drain directly into the disposal if you choose to do it that way.
The plumber should have plenty of room under the sink to properly attach and slope the P trap and drain line.
Just make sure the new sink is the same dimensions and mount style (top mount, undermount) as the old one.
Just reviewed the new pictures and info you added. I won't go into the required specs for a P trap but I would suggest that if you decide to go with a deeper sink than the one you have now that you talk with your plumber first. It appears from the pictures that you might be able to go an inch or two deeper but any more than that could be a problem for proper installation of the P trap.

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  • I've updated the image-- my fault, I thought that image was correct when I posted it. I believe that to be a top mount, and I am only considering top mounts for that reason. Also, thank you for the correction in terminology, I will fix that shortly.
    – Reader
    Nov 27, 2022 at 23:55
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You're missing one picture -- the one taken at an angle to show the plumbing behind the vertical center-post in the cabinet doors, connecting the disposal to the wall.

I assume that there is a wye fitting ('Y' fitting) joining the drain from the left and right sinks located there on the right side, just inside the cabinet. What I cannot see is whether the wye is in the rough/schedule-40/glue-joint part of the plumbing (in the wall) or in the finish/cheap "plastic" crap/slip-joint part of the plumbing (from the sink to the adapter).

There are two issues your plumber will face. First, the vertical height between the bottom of your (new) sink and the place where the drain(s) enter the wall. Second, closing any holes in the system left by converting from two drains to just one.

Vertical drop

The images you provided do not make clear the depth of your sink. I can believe the existing sink is 6" deep or 8" deep. I'd be a little surprised if the existing sink was 10" deep, and shocked if the existing sink was 12" deep.

OTOH, the amazon link claims the new sink will be 10" deep.

So it seems likely the new sink will either be the same as the old sink (10") or 2-4" deeper than the old sink (10" vs 6-8"). I don't know if the garbage disposal drain has 2" to spare. It looks like 4" would be a total show-stopper.

Get you a tape measure or two rulers, and measure from the floor of the cabinet (I assume it's level) to the bottom of the disposal drain outlet and the bottom of the drain pipe at the wye fitting. The disposal should be higher than the fitting, the question is how much higher. That's the amount of "slack" you have to lower the disposal (lowering the sink will force the disposal lower). If the new sink will be 4" lower than the old sink, you had better have 4.25" of height difference. If the difference is 0" because the new and old sinks are both 10", then you're golden.

Closing the old drain

If you have two drains in the wall, which I don't believe is the case, or if your wye fitting is in the rough plumbing -- schedule 40 PVC (white) or ABS (black) pipe in the wall, or even copper or cast iron or galvanized steel -- then the solution will be to plug (if female) or cap (if male) one of the old openings, or to divide the disposal/dishwasher between the two. There are standard fittings to do both, so this will just be a case of buying existing fittings and installing them. These will be "rough plumbing" fittings, and so relatively cheap.

If you have a single drain in the wall, with the wye being made from the thin-walled plastic crap, then your problem disappears when the plastic crap gets yanked out. Cost would be zero. (This is probably not the case.)

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  • Updated with two additional pictures: One as you suggested, at an angle; the other of a label beneath one of the basins. Unfortunately, the label has only helped me identify the brand as Franke-- it has not yielded a model number or the depth.
    – Reader
    Nov 28, 2022 at 4:31
  • Also, I took some measurements, but I think I took them incorrectly. Can you clarify: The bottom of the disposal drain outlet would be the bottom of the black tubing coming out of the side of it? And the bottom of the wye would be the bottom of the white tubing exactly as it joins the cabinet? (I.e., not concerned about the lowest points of the dips?)
    – Reader
    Nov 28, 2022 at 4:34
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    Depth of sink .vs. height of drain opening is the big issue that can make the change difficult or expensive, especially with a garbage disposal. +1
    – Ecnerwal
    Nov 28, 2022 at 13:27
  • @Reader, you are correct: the bottom of the black plastic drain just as it leaves the disposal, and the bottom of the white drain just as it enters the wye fitting. My expectation (obviously) is that this is a downhill slope from the disposal to the drain. (The "dips" would be P-traps, and no, they don't matter for this.)
    – aghast
    Nov 29, 2022 at 14:27
  • Thank you. It is a vicious measurement to take because of how the pipes run, but there is about a 2" delta. My guess is also that the sink depth is 8", and so I've changed my intended purchase to a 9" deep sink to be conservative. Thank you very much.
    – Reader
    Nov 29, 2022 at 20:28
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What you described should be an easy job for a plumber. I like to have the materials in hand prior to scheduling the work.

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  • A thought here in Germany: we had most of the house replumbed. The plumbers did not even contemplate installing anything we bought ourselves. It had to be quality stuff from the plumbing wholesaler. We were allowed to visit the showroom and pick out the stuff we liked. They then ordered and delivered it (at trade price), and any problems about fit and function were neatly transferred to them.
    – RedSonja
    Nov 28, 2022 at 9:23
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    @RedSonja: I had a similar replumbing here in France. We showed the plumbers what we wanted to have and they were fine, except in places where it was not doable (for technical reasons they explained to us). they also made us change our minds in another case where what we wanted would be, from their experience, a problem long-term. I wonder if we were just lucky.
    – WoJ
    Nov 28, 2022 at 11:39
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Sometimes going to a deeper sink will cause problems hooking up the disposal. Your existing sink looks pretty deep so as long as the new sink is not deeper you should be fine.

Another thing I noticed is this looks like an island. If it is then I don't think your sink is vented properly. Probably not a major issue but something the plumber will want to correct with an air admittance valve.

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