Undermount sink issue

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tailgunner

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Had the undermount stainless sink separate from the granite countertop this morning . Luckily there is a pull out garbage can under there to help support the weight of the disposal. I am looking for ideas on the best way to reattach the sink. Would I need to disconnect the disposal ? I assume I would need a good epoxy to reglue it ?
Thanks in advance for your input
 

Jamesplumbing06

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You need a granite forum. But yeah turn off valves in cabinet and disconnect the plumbing for disposal. Measure the inside width of cabinet. Cut 2 - 2x4 that length. Remove adjacent drawers. Get sink back in position then insert 2x4’s under rim of sink and screw from each drawer opening to your 2x4. I use “lexel” or “through the roof” hand tube caulk and seal the seam between top and sink. Hook your disposal back up.
 

Mikey

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Most undermount fixtures come with clips used to hold the fixture in place. Most installers throw the clips away and just use a good adhesive caulk. I've always had doubts about the caulk, but after having had to remove a caulked-in sink, I was a believer. But, the caulk left over from last year's base mold install won't do. Moen recommends 100% silicone caulk, but there are several brands out there which specifically target undermount applications. The basic process is well documented in YouTube videos.
 

Mitchell-DIY-Guy

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I’ve had this professionally done twice recently in two locations with different sinks and contractors. Both used some two-part goop-a polyester or epoxy compound—definitely NOT caulk or silicone.
 

tailgunner

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There were no clips on mine . Just pieces of wood epoxied in place. I plan on using these, looks like a good solution.

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All the granite tops I've seen were glued to a plywood base with the sink sandwiched between the wood and the Granite. The sealant was put between the sink and the granite but only as a seal. The weight of the sink was supported by the plywood. You happen to have a stainless sink but don't forget others might have a cast iron one. Full of water a cast iron sink could weigh well over a hundred lbs. Best listen to what JamesPlumbing has to say. Clips are usually for bathroom sinks
 

Jamesplumbing06

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Just think. Epoxy is why your in this mess. Epoxy is holding the scrap pieces of wood to anchor the sink 🤔🤔. Epoxy is a no no. Stay away from trusting epoxy or any kind of caulk, glue. Build a structure to hold that sink in place. Then seal with your choice of caulk. Even good granite guys will tell you the same thing. My father in law is a granite and tile guy. He lost faith in epoxy long time ago.
 

Mitchell-DIY-Guy

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Actually best to follow manufacturers recommendations. This photo is of the prep work done for a Ruvati apron front farmhouse kitchen sink in SS. They call for a supporting frame so I built one out of hardwood and mounted to the base cabinet. Provides full support. This is actually a flush mount installation. Yes the cabinet is packed underneath. The disposal, an air switch for same, an RO drinking water system, a detergent dispenser, faucet, plus the normal plumbing stuff.
 

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tailgunner

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That looks like a great way to go, but how do you fasten the frame to the cabinet sides. The side is flimsy and thin, and doesn't seem to allow a good base to attach the frame. Bob
 

Mitchell-DIY-Guy

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@tailgunner what you cannot see in the photos are four uprights made of 1x3 poplar. These are at each corner of the cabinet. They support another 1x3 on R and L sides, providing “rails” on either side. The frame sits on these rails. Everything had to be made to fairly tight tolerances. Here’s a view of the right side; the black box is the air switch. Unfortunately the forum rotated the photo.
 

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Yes, or about 10 pounds per clip. Or about 1.2 lb/sq inch load on the adhesive used on a typical sink (I used a Kohler K-5540 as an example).
The water alone in a K-5540 would weigh 188 lbs. in a K-5950 Cast Iron sink the total would be 230 lbs. And thats without somebody pressing down to scrub a pot.
 

tailgunner

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First of all , thanks for taking the time to take the photos and posting, your help is very much apprciated. I see what you did with the vertical 1x3's . But what about attaching those to the thin walls of the cabinet?
 

Jamesplumbing06

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Screws and a second sandwich block on opposite side of cabinet walls. A granite guy will go a long way. They aren’t terribly expensive.
 
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