Install an Overmount Sink
1. If you're replacing your existing sink with one that's the same size and shape, turn off the water supply to the sink, disconnect the water supply lines and drain pipe, loosen the sink from the countertop, and lift it up. Note: Some sinks are held in place with special clips on the bottom. If your sink has these, you will need to remove them before you can lift out the sink. Also, your sink is probably secured with a bead of latex caulk or plumber's putty under the outside edge. Slide a knife blade under the flange all around the edge to loosen it.
2. If you are installing a new sink, you will need to decide on the shape and material for the new sink. Kitchen sinks come in all kinds of designs - single bowl, double bowl and even triple bowl - as well as many different materials, such as stainless steel or enamel.
3. If you are going to use your existing countertop, make sure the holes in the sink for the faucet align with your faucet and the countertop. Kitchen faucets are commonly 8 inches, but some are slightly different.
4. Most new sinks come with a template for installing them. Position the template on your countertop, mark the outline and you're ready to go. If your new sink didn't come with a template, it's not a problem. Simply turn your new sink upside down on the countertop and draw a line around the edge of the sink. Then mark a second line about 1/2" inside the first line. This will be the line you cut along, since the sink has a flange that needs to overlap onto the counter surface to support the weight of the sink.
5. Cutting the hole for the sink is straightforward. Drill 3/8" holes at the corners of the outline. These will allow you to insert your saber saw blade to start the cut and also permit cutting around corners without the saw blade binding. You will also drill holes though the countertop to allow the water supply lines to get to the faucet.
6. Using denatured alcohol on a rag, clean the top surface of the counter top around the hole, the underside of the sink flange, and the bottom of your faucet and sink features.
7. Apply a bead of latex caulk or plumber's putty to the faucet base and attach it to the sink while you have easy access to the underside of the sink. This is also a good time to attach the flexible water supply lines to the base of the faucet's water supply tubes. These lines usually attach with pressure couplings, which you can screw on by hand and then give a final (gentle) tightening with a wrench.
8. Turn the sink over and position it into the hole, while threading the water supply lines through the holes drilled for them earlier. Press down on the sink to ensure the caulk is evenly spread. If any oozes out around the edges, wipe it up with a clean cloth now to avoid a messy clean up later.
9. Some sink manufacturers provide fastening clips to hold the sink in place. If you have them, now is the time to attach them.
10. After the sink is in place, install the sink drain. Put plumbers putty on the bottom of the drain assembly and push it down into the drain opening in the bottom of the sink. There is a lock nut that tightens on the outside bottom of the sink to hold the drain in place, so tighten it as well.
11. Allow the caulk and plumber's putty to set up over night. Then attach the water supply lines from the faucet to the home water supply. These are usually attached with pressure couplings that should be tightened with your wrench.
12. Assemble and attach the S trap and drainpipe to the sink bottom and the household drainpipe.
13. Fienally, turn on the water and look for leaks. If there are any, tightening the pressure couplings gently will usually stop them.
So there you go. What seemed like an intimidating project with a little planning and some simple tools becomes a weekend project that a DIY'er can take on with confidence.