Plumbing in the Home/Cast iron kitchen sink


When installing a new cast iron sink in a cut-out hole in a new laminate counter top, what is the recommended method of caulking at the edge/lip of the sink to prevent any back flow of moisture into that area in the future? Also, what type of caulk is best, one that hardens up, or one that remains flexible?  To your knowledge, is there an "industry standard" for this procedure with regards to cast iron sinks?  Thanks

Hi David,
The method of installation (and caulking) depends on several things; is this a top mount sink, and under mount sink, or a sink that installs with a metal rim?

Cast-iron sinks are very heavy, obviously, and not easy to handle in an awkward position. Planning and dry fitting to make sure nothing is in the way is most important.

If this is a top mount style sink, one that has a rounded "bull nose" rim, This is the method that I follow;
1. I typically install the faucet and secure it well as it provides a bit of a handle for maneuvering the sink.

2. I DO NOT install the drain fittings. This provides a handhold other than the actual rim with which to lift and place the sink in the opening. Installing the drains after the sink is set is pretty easy, installing the faucet, not so much.

3. Depending on the color of the counter top I either use white or colored silicone caulk. It is the most durable and long-lasting and remains a bit flexible.

4. With the sink sitting on the floor on a large piece of cardboard to protect its finish, upside down and at an angle resting on its front rim, with a cardboard box or something to support the back edge off the floor so that the faucet is not damaged, I apply an even bead of caulk around the flat underside of the rim that will come in contact with the counter top. (now you see why I leave the drains open for handholds)

5. I then reach underneath and grab the sink through the drain openings, pick it up and carefully center and lower it into the opening in the counter top. (If this is a large two or three bay kitchen sink, I will sometimes use two people to pick it up and set it. Occasionally I will have the second person on their back under the sink cabinet to help support the weight of the sink from below as I lowered it into position. Obviously, this is only safe if it's the type of sink that cannot drop through the hole and injured this person)

At this point,once actually sitting on the counter top, I step back and eyeball it for alignment to make sure it is sitting square and parallel to the front edge of the counter top and to the backsplash. You can bump it around a bit for alignment but not too much.

6. I wipe off any excess caulk that may have extruded out onto the counter top. Silicone caulk can be easily cleaned up before it sets using mineral spirits if needed. Once it sets up, you will need to scrape it off with a razor blade. I allow the sink to sit undisturbed for a couple of hours to allow the caulk to set up.

7. At this point, I typically install the 3 inch basket drain(s) and/or the disposer drain body if you're installing a disposer.

8. Now, starting from the back wall and moving forward I begin to hookup water supplies, dishwasher drain hoses to the air gap, dishwasher hot-water supply and then finally I hang the disposer, connect the large diameter drain hose from the air gap to the disposer and lastly I install the drain piping and connected to the drain outlet sticking out from the wall. If this is a new disposer, do not forget to knock the slug out of the inside of the drain inlet or the dishwasher will not drain and all the water will just squirt out the top of the air gap when you run the dishwasher. This outlet comes plugged from the factory because not all installations include a dishwasher.

9. The last thing I do is run a small bead of caulk around the entire rim of the sink where it meets the countertop and either smooth it with my finger or a tool. This provides a nice clean fillet of caulking between the edge of the sink and the countertop. It also seals any exposed cast-iron that may not have gotten porcelain coated so that it will not rust in the future.

Because of all of the systems like garbage disposer's, dishwasher supplies and drains, hot water dispensers, drinking water filters etc., setting finish on a kitchen sink installation can be one of the most time-consuming processes and can take several hours to complete.

Have fun!

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Dana Bostick


Pretty much any residential plumbing questions. For "item specific" details such as a specific model of fixture, I will need to research and there may not be any useful information available. Note: I live and work in Southern California. We do not, as a rule, use hot water or steam heating systems, oil fired boilers or private water wells so my knowledge in those areas is pretty limited. There are others here on AllExerts that can probably answer those questions better.


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