What you need to know before you start

Replacing a faucet is a job most homeowners can do in an afternoon with basic tools—no plumbing license required. The hardest part is usually getting the old faucet out from under the sink, not putting the new one in. You will need an adjustable wrench, a basin wrench (a specialized tool that costs about $15 and makes the job much faster), a bucket to catch water, and possibly a screwdriver. Most new faucets come with everything else: supply lines, mounting hardware, and instructions specific to that model.

The process breaks into three stages: shutting off the water and removing the old faucet, preparing the sink, and installing the new one. If you hit a stuck bolt or a corroded connection, you may need to call a plumber—that is not a failure, it is knowing when the job has changed. But the majority of faucet swaps go smoothly if you follow the steps in order and do not force anything.

Key Takeaways

  • Turn off the water supply under the sink before you disconnect anything, and turn on the faucet to release pressure in the lines.
  • A basin wrench—a tool designed specifically for faucet work—will save you hours of frustration reaching bolts under the sink.
  • Most new faucets come with flexible supply lines already attached, so you only need to hand-tighten them to the shutoff valves.
  • Test for leaks at the shutoff valves and the base of the faucet before you consider the job done, because small drips are easier to fix now than later.
  • If bolts are stuck or corroded, stop and call a plumber rather than risk cracking the sink or stripping a bolt.

Shut off the water and drain the lines

Look under the sink. You will see two shutoff valves—one for hot water, one for cold—attached to the supply lines coming from the wall. Turn both valves clockwise until they stop. You do not need to force them; hand-tight is enough. If the valves are missing or will not turn, you will need to shut off the main water supply to the house, which is usually in the basement or outside. That is a good sign you should call a plumber for this job.

Once the valves are closed, go back to the sink and turn on the faucet. Let the water run until nothing comes out. This releases the pressure in the lines so you do not get sprayed when you disconnect them. Leave the faucet in the on position while you work.

Disconnect the old supply lines and mounting bolts

Place a bucket under the shutoff valves. Use an adjustable wrench to loosen the nuts where the supply lines connect to the valves—turn counterclockwise. They will not come off completely; just loosen them enough that you can unscrew them by hand. Water may drip out; that is normal. Unscrew the nuts the rest of the way and set the supply lines aside.

Now you need to reach the bolts that hold the faucet to the sink. These are under the sink, behind the faucet. This is where a basin wrench earns its cost. It has a long shaft and a small head that fits into tight spaces. Slide it up behind the faucet until the head grips the bolt, then turn counterclockwise. If you do not have a basin wrench, an adjustable wrench or pliers will work, but you will be working in an awkward position. Loosen both bolts—usually there are two, sometimes three—until the faucet lifts away from the sink. If a bolt will not budge after a few tries, stop and call a plumber. Forcing it can crack the sink or strip the bolt.

Clean the sink and prepare for the new faucet

With the old faucet out, you will see the mounting holes in the sink and probably some old caulk or mineral buildup around them. Scrape away any old caulk with a putty knife or old credit card. Wipe the area clean with a damp cloth and let it dry. If the sink has three holes and your new faucet uses only two, you can leave the extra hole empty or cover it with a decorative cap that usually comes with the faucet.

Check the new faucet's instructions now, before you install it. Different models mount differently—some have a rubber gasket that goes on top of the sink, others have a metal plate underneath. Knowing what you are doing saves time and prevents mistakes.

Install the new faucet and reconnect the supply lines

Most new faucets come with flexible supply lines already attached to the base. Lower the faucet through the mounting holes in the sink. From underneath, slide the rubber gasket or mounting plate onto the bolts, then hand-tighten the bolts until the faucet sits flat against the sink. Use the basin wrench to tighten them a bit more—snug, not cranked down. Over-tightening can crack the sink or strip the bolts.

Now connect the supply lines. The hot line (usually red or marked with an H) goes to the hot shutoff valve. The cold line (usually blue or marked with a C) goes to the cold shutoff valve. Hand-tighten the nuts first, then use an adjustable wrench to tighten them another quarter turn. They should be snug but not so tight that you need a wrench to loosen them later.

Turn the water back on and check for leaks

Turn both shutoff valves counterclockwise to open them. Water will flow into the faucet. Turn the faucet handle to hot and cold a few times to fill the lines and remove air. Watch under the sink for drips at the supply line connections and at the base of the faucet. A small drip at a connection usually means the nut needs another quarter turn. A drip at the base of the faucet usually means the gasket is not seated properly—you may need to tighten the mounting bolts a bit more or reseat the gasket.

Let the water run for a minute, then check again. If everything is dry, you are done. If water is still dripping, turn off the shutoff valves and tighten the connection or bolt that is leaking. Small leaks are much easier to fix now than after you have put everything back in the cabinet.

Reconnect the drain and cabinet (if applicable)

If you removed the drain P-trap to access the faucet bolts, reconnect it now. Hand-tighten the nuts, then use an adjustable wrench to snug them. Do not over-tighten—you want to be able to loosen them by hand if you ever need to clear a clog. Run water through the sink and check for leaks at the drain connections.

Put back any cabinet doors or panels you removed, and you are finished. The faucet is ready to use.

When to call a plumber instead

Stop and call a plumber if the shutoff valves will not turn or are missing. If the mounting bolts are stuck and will not loosen after a few gentle tries, stop—forcing them risks cracking the sink. If the old supply lines are corroded or brittle and break when you try to disconnect them, a plumber has the tools to remove them safely. If water continues to drip from the base of the faucet after you have tightened the mounting bolts, the sink may be warped or the gasket may be damaged in a way that requires professional repair.

A plumber visit for a faucet replacement usually takes 30 minutes to an hour and costs between $150 and $300 depending on your area and the faucet model. That is worth it if the job has complications or if you are not comfortable working under a sink.

Frequently Asked Questions

Do I need to turn off the main water supply?

Only if the shutoff valves under the sink are missing or broken. If they work, use them—it is faster and does not affect the rest of the house. If they do not work, you will need to find the main shutoff, which is usually in the basement, crawlspace, or outside near the meter.

What if the faucet leaks from the base after I install it?

First, tighten the mounting bolts a quarter turn at a time until the leak stops. If it still leaks, turn off the water, loosen the bolts, and check that the rubber gasket is centered under the faucet. Reseat it and tighten the bolts again. If it leaks after that, the sink may be warped or the gasket may be defective—call a plumber.

Can I use the old supply lines with a new faucet?

Only if they are in good condition and the right length. Most new faucets come with new lines, which is safer because old lines can be brittle or corroded inside. If you must reuse old lines, inspect them first for cracks, kinks, or mineral buildup.

How tight should the supply line nuts be?

Hand-tight plus a quarter turn with a wrench. If you over-tighten, you can crack the fitting or strip the threads, making it impossible to disconnect later. You should be able to loosen the nut by hand if you ever need to.

What if water sprays out when I disconnect the old supply lines?

That means the shutoff valves did not close completely or the pressure did not release. Turn off the main water supply, then try again. If the valves are leaking, they may need to be replaced—a plumber can do that while they are there.