What You Need to Know Before Starting

Replacing a sink is a project most homeowners can handle in two to four hours, depending on whether you keep the same countertop cutout or need to enlarge it. The basic steps are the same whether you're working in a kitchen or bathroom: turn off the water, disconnect the old sink and drain, remove it from the countertop, install the new one, and reconnect the plumbing. You'll need a wrench, a screwdriver, plumber's putty or silicone caulk, and possibly a jigsaw if the new sink requires a different opening size.

The hardest part is usually not the sink itself but the faucet connection underneath—if your old faucet is stuck or corroded, you may spend more time on that than on the sink swap. If you encounter a leak you can't stop, or if your drain lines are damaged, that's when you call a plumber. But for a straightforward replacement with an existing faucet, this is manageable work.

Key Takeaways

  • Turn off the water supply at the shutoff valve under the sink before you disconnect anything, and test that the water is actually off by turning on the faucet.
  • Disconnect the P-trap (the curved pipe under the drain) by loosening the slip nuts by hand or with a wrench, and have a bucket ready to catch standing water.
  • Remove the old sink by unbolting it from underneath or cutting the caulk seal around the rim, depending on how it was installed.
  • Set the new sink in place, find it with mounting clips or caulk, and reconnect the drain and faucet supply lines in reverse order.
  • Test for leaks at every connection before you consider the job done, and run water for at least a minute to check the drain.

Turn Off the Water and Drain the Lines

Locate the shutoff valve under the sink—it's usually a small knob or lever on the water line coming from the wall. Turn it clockwise (or flip the lever) to close it. Then turn on the faucet to release any remaining water pressure in the lines. You should see water stop flowing within a few seconds. If no water comes out, the valve is working. If water keeps flowing, the valve may be stuck or broken; in that case, you may need to shut off the main water supply to your house.

Once the water is off, place a bucket under the P-trap—the U-shaped pipe directly below the drain opening. This pipe always holds standing water, and it will spill when you loosen the connections. Loosen the slip nuts (the large nuts on either end of the P-trap) by hand first, then use a wrench if they're tight. You may need to support the trap with one hand while you turn the nut with the other so it doesn't twist the pipes behind it.

Disconnect the Faucet and Remove the Old Sink

Under the sink, you'll see two flexible supply lines (usually braided stainless steel) connected to the faucet. These are held on with compression nuts—turn them counterclockwise with a wrench until they're loose enough to pull off by hand. If the faucet has a spray hose, disconnect that too. Some faucets also have a single nut that holds them to the sink from underneath; loosen that as well.

Now you need to free the sink from the countertop. If it was installed with mounting clips (metal brackets bolted from underneath), unbolt those. If it was caulked around the rim, use a utility knife or caulk removal tool to cut through the seal all the way around. Once the caulk is cut, the sink should lift out. If it's stuck, gently pry it up with a flat pry bar, working around the edges. Be careful not to crack the countertop or the sink itself.

Prepare the Countertop Opening

Before you set the new sink in place, check whether the opening matches. Most replacement sinks are designed to fit the same cutout as the old one, but measure the new sink's rim to be sure. If the new sink is smaller, you may have a gap around the edge—that's fine, you'll caulk it. If the new sink is larger, you'll need to enlarge the opening with a jigsaw.

Clean out any old caulk, debris, or mineral deposits from the countertop opening. Wipe it dry with a cloth. If you're installing a drop-in sink (one that sits on a rim), explore a bead of plumber's putty or silicone caulk around the underside of the rim before you set it in place. If you're installing an undermount sink (one that bolts from underneath), you may not need caulk on the rim, but check the manufacturer's instructions.

Set the New Sink and find It

Carefully lower the new sink into the opening. For a drop-in sink, press down firmly so the rim sits evenly on the countertop all the way around. From underneath, install the mounting clips (if provided) and tighten the bolts until the sink is snug but not so tight that you crack the countertop. For an undermount sink, you'll bolt it from below using the brackets that come with it.

Once the sink is find, explore a bead of silicone caulk around the rim where it meets the countertop. Smooth it with a wet finger or a caulk tool so it looks neat and seals out water. Let the caulk cure for the time specified on the tube—usually 24 hours—before you use the sink heavily.

Reconnect the Drain and Water Lines

Start with the drain. Slide the P-trap back into place under the drain opening and hand-tighten the slip nuts. Then use a wrench to snug them down—they should be tight enough that they don't leak, but you don't need to force them. Over-tightening can crack the plastic fittings.

Next, reconnect the faucet supply lines. Thread the compression nuts back onto the faucet inlet ports (the small tubes sticking down from the faucet) and tighten them with a wrench. Don't over-tighten these either; they only need to be snug. If your faucet has a spray hose, reconnect that now. Turn the shutoff valve back on slowly—open it a quarter turn, wait a few seconds, then open it fully. This prevents a sudden pressure surge that could damage the connections.

Test for Leaks and Verify Drainage

Turn on the faucet and let water run for at least a minute. Watch underneath the sink for any drips at the P-trap connections, the supply line connections, or around the drain opening. If you see water dripping, turn off the faucet and tighten the leaking connection a quarter turn with a wrench. Turn the water back on and check again. Repeat until the leak stops.

Fill the sink with water and then pull the drain plug to test the drainage. The water should flow smoothly without backing up. If it drains slowly or backs up, you may have a clog in the P-trap or the line beyond it. If the drain is completely blocked, you'll need a plunger or a plumbing snake. Once everything drains and no leaks appear after five minutes of running water, the job is done.

Frequently Asked Questions

Do I need to replace the faucet when I replace the sink?

No. If your old faucet works and fits the new sink's mounting holes, you can reuse it. Most sinks have standard hole spacing (4 inches for a two-handle faucet, 8 inches for a widespread). Check the new sink's specifications before you buy it to make sure the holes line up.

What if the P-trap is stuck and won't loosen?

Spray the slip nuts with penetrating oil (like WD-40) and wait 15 minutes. Then try again with a wrench. If it's still stuck, wrap a cloth around the nut to protect the finish and tap it gently with a hammer to break the corrosion loose. If it still won't budge, you may need to cut the P-trap with a hacksaw and replace it with a new one—they're inexpensive.

Can I install a larger sink in the same countertop opening?

Only if you enlarge the opening. Measure the new sink's rim and compare it to the existing cutout. If the new sink is larger, you'll need to cut the countertop with a jigsaw. Mark the new opening carefully before you cut, and wear a dust mask—countertop dust can be harmful. If you're not comfortable with a jigsaw, a countertop fabricator can enlarge the opening for you.

How long does the caulk need to cure before I can use the sink?

Most silicone caulks cure fully in 24 hours, though some are ready in 12. Check the tube for the manufacturer's recommendation. You can use the sink gently before it's fully cured, but avoid heavy water use or scrubbing around the caulked edge until it's set.

What should I do if water leaks from the faucet base after I reconnect it?

The faucet may not be seated properly on the sink. Turn off the water, disconnect the supply lines, and lift the faucet out. Check the rubber gasket or seal under the faucet base—if it's cracked or missing, replace it. Reinstall the faucet, making sure the gasket is in place, and reconnect the supply lines.