I am in the process of replacing a laminated countertop at an apartment with a granite countertop. Currently there is a drop in SS sink as shown below. This sink is 8" deep.



The countertop installer says it will look nice with an undermount sink, which I agree. However I have two concerns.

(1) Tenant tend to abuse the property, not all of them, but typically they will not take good care and I think a drop in sink is more "bullet proof" compared to an undermount, as an undermount is held by clips on the underside epoxied to the counter.

(2) Is my drain low enough to handle an undermount? So I need to do some calculations. First off, the current laminated counter is 1-1/2" thick, and the sink sits on top of that. An undermount will go below that so an undermount will take the bottom of the sink 1-1/2" lower to start with. In addition, I found most undermount SS sinks are 9" or 10" deep nowadays, so if I go with a 10" deep sink, the bottom of the drain will be 3-1/2" lower than my current setup. Will this work?

Here is a photo of the drain setup below. The outlet of the disposer is 3-1/2" higher than the drain at the back of the cabinet, so if I use a 10" undermount sink, the disposer outlet will be the same as the wall drain, so it won't work I don't think.



But when I took a closer look, I think the real limit here is the distance from the bottom of the disposer outlet elbow, is 2" higher than where it enters the p-trap U-bend. In other words, I don't think I can lower that disposer more than 2" if I want to keep that elbow.

If the disposer can't go more than 2" lower, and an undermount sink is already 1-1/2" lower, I must use an 8" undermount sink right?



But if I stay with a drop in sink, I can go with a 10" deep sink with no issue with vertical clearance.

The counter estimator told me "you have plenty of room and using a 10" undermount sink is perfectly fine, it's standard and I have been doing this for 25 years". Is he right or am I right?



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Sum, are you sure that laminated top is 1 1/2" thick? All that I've seen are 3/4" particleboard and there's a 3/4" or 1/2" strip added to the front overhang. All the stone tops I've dealt with required a plywood substrate(usually 5/8" ) installed on top of the cabinets. With this scenario, the bottom of the sink height will be close to the same as existing.



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steve,

there may be differences in regional practices, but yes down here in south Florida, the wood laminate is 1-1/2" thick.



It has two layers...basically a layer of 3/4" plywood, and on the underside strips of 3/4" furrings if you will. Here is a picture of a laminated wet bar showing the underside on how they do it. So in this case, the drop in sink sits 1-1/2" above the top of wall or cabinet.



When they do solid stone like granite or quartz, that is either 2cm or 3cm thick, it is laid directly on top of the cabinet or wall with no wood substrate at all. So an undermount sink's level will be the same as the top of the cabinet, unless the slab is shimmed to level in some spots.

So, if I were to use an 8" deep sink but instead of drop in I do the undermount, the entire sink will be 1-1/2" lower than before. If you look at this picture where I measured the bottom of the disposer outlet elbow to the top of the P-trap inlet, that is only 2". That tells me for an 8" undermount sink, that elbow will insert 1.5" lower, leaving only 1/2 left. If I go with a 10" sink, and undermount it, that elbow coming out of the disposer will be lower than the cabinet drain inlet.





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Looks like you're stuck wih the 8".

An alternative might be to use a different disposer, with a higher outlet. The ones controlled by a separate switch vs stopper controlled, have a higher outlet.