How to Install a New Faucet

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The part of a faucet swap that decides everything happens before you ever pick up a wrench: the new faucet has to match the holes already drilled in your sink or countertop. Get that wrong and the box goes back to the store. Get it right and the rest is a deck-mounted job you can finish from below in an afternoon, with the water shut off at the stops under the sink and nothing soldered or opened inside a wall.

This guide walks the full replacement on a kitchen or bathroom sink: confirm the mounting pattern, close the supply stops, drop the old faucet out from underneath, clean the deck, set and secure the new one, connect the supply lines, and prove every joint holds under pressure. If you are only chasing a drip rather than replacing the whole fixture, see our guide on how to fix a dripping faucet (022). If the faucet works and you just want to swap the worn cartridge inside it, see our guide on replacing a faucet cartridge (025). Picking the type, finish, and hole layout in the first place is covered in our guide on choosing a kitchen or bathroom faucet (027).

Matching the New Faucet to the Sink’s Hole Configuration (Single, Centerset, Widespread)

Count the holes in your sink and measure between them before you buy. Faucets are sold in three common deck patterns, and they are not interchangeable without a workaround.

A single-hole faucet mounts the spout and handle through one opening. A centerset faucet is built on a single base plate that spans three holes set four inches apart, center to center, with the spout and both handles tied together. A widespread faucet uses three fully separate pieces, a spout and two handles, connected by hoses underneath, and the outer holes are typically eight inches apart or more.

The measurement that matters is center to center between the two outermost holes. A four-inch spread points you to a centerset or a single-hole faucet with a deck plate; an eight-inch spread points you to a widespread set. A single-hole faucet can usually drop into a three-hole sink if it comes with an escutcheon (a deck plate) to cover the two unused openings, but a widespread faucet will not fit a four-inch sink, and a centerset will not bridge an eight-inch one. If you have not chosen the faucet yet, settle the hole layout, type, and finish first using our guide on choosing a kitchen or bathroom faucet (027), then come back here to install it.

While the faucet is out of the box, this is also the moment to confirm it is certified lead free for drinking water. Under the federal Safe Drinking Water Act, faucets and fixtures that carry water you drink must meet a weighted average of no more than 0.25 percent lead across their wetted surfaces, and certification to that limit has been mandatory since September 1, 2023. Any faucet sold for potable use today is built to that standard, so this is mostly a reason not to reinstall a very old salvaged faucet on a drinking-water line.

Flow rate is the other spec worth a glance before you install. Federal standards have capped both kitchen and bathroom faucets at a maximum of 2.2 gallons per minute since 1994, according to the U.S. Department of Energy. A faucet carrying the EPA WaterSense label uses no more than 1.5 gallons per minute at 60 psi, which trims a bathroom sink’s flow by about 30 percent with no real loss in performance. The number is set at the factory by the aerator on the spout, so it is not something you change during the install, but it is worth knowing what you are putting in.

Shutting the Supply Stops and Disconnecting the Old Faucet From Below

Turn off the water before anything else. Reach under the sink, find the two shutoff valves (angle stops) on the hot and cold supply lines, and turn each one clockwise until it stops. Open the old faucet at the top to release pressure and confirm the water is actually off. Then put a bucket and a towel under the connections, because the lines and the faucet body still hold water that will spill when you loosen them.

Disconnect the flexible supply lines where they meet the angle stops, then where they meet the faucet’s tailpieces, catching the trapped water as you go. If your old faucet has a sprayer or a pull-down hose, disconnect that too. Clear everything out from under the sink so you have room and light to work, and lay down a towel to lie on.

One caution belongs here. If an angle stop is corroded and will not turn, or it weeps from the stem when you try to close it, stop and deal with the valve first. Forcing a seized stop can break it while the line behind it is still under pressure. Replacing a toilet or under-sink shutoff that will not close is its own job, covered in our guide on replacing supply lines and shutoff valves (196). Do not try to power through a stuck valve to start a faucet swap.

Removing the Old Faucet and Cleaning the Deck of Old Sealant

Underneath the sink, the old faucet is held by mounting nuts threaded onto its tailpieces or mounting studs. Loosen those nuts and the faucet lifts straight up off the deck. The catch is reach: those nuts sit deep behind the basin, crowded by the bowl, the drain tailpiece, and the supply lines, and a standard wrench cannot get a square grip on them.

This is where a basin wrench earns its place. It has a long shaft with a spring-loaded jaw that pivots to grab a nut you cannot see, and a T-handle at the bottom so you can apply turning force from below. You work largely by feel. Position the jaw on the nut, confirm it has bitten, and turn. Old nuts may be stiff or rusted; penetrating oil and patience beat brute force here.

Once the faucet is out, scrape the deck clean. Old faucets are bedded in plumber’s putty or a silicone sealant, and dried sealant left on the surface will keep the new faucet’s gasket from seating flat, which is a common cause of a base that wobbles or weeps later. Remove every ridge of old putty or caulk, wipe the area down, and let it dry. A clean, flat deck is what lets the new seal do its job.

Setting and Securing the New Faucet With Mounting Nuts and a Basin Wrench

Dry-fit first. Set the new faucet on the deck, feed its supply tubes and any mounting hardware down through the holes, and check that it sits square and faces straight before you commit. Many modern faucets come with a rubber or foam gasket already attached to the base; if yours instead calls for a bead of sealant, follow the manufacturer’s instructions for that specific model, since some bases are designed to seal dry and adding putty can interfere with the fit.

With the faucet positioned, go back underneath and thread on the mounting nuts or the mounting plate by hand first, then snug them with the basin wrench. Tighten enough to lock the faucet from sliding or rotating on the deck, and no more. Many mounting nuts today are plastic, and overtightening can strip the threads or crack the nut. The target is firm and immovable, not crushed. Have a helper hold the faucet straight from above while you tighten, so it does not rotate off center as the nuts draw down.

Connecting Supply Lines and Sealing the Threads Correctly

Connect hot to hot and cold to cold. Standing at the faucet, the hot side is on your left and the cold on your right; the supply tubes or tailpieces are usually marked. Run a new flexible supply line from each angle stop up to the matching faucet connection. New braided stainless lines are inexpensive and worth fitting rather than reusing old ones that may have been kinked or stressed during removal.

How you seal each end depends on the fitting, and this trips up more first-time installs than anything else. Most supply-line and angle-stop connections are compression fittings, and a compression fitting seals by squeezing a ring against the tube as you tighten the nut, not at the threads. On those connections you add no thread tape at all; tape on compression threads can actually keep the joint from seating and cause a leak. Thread seal tape (PTFE tape) belongs only on tapered threaded joints, the kind where a male threaded end screws into a female fitting. Wrap that style two or three turns in the direction the nut tightens, and leave compression nuts bare. Tighten each connection by hand, then bring it firm with a wrench, snug rather than gorilla-tight.

Pressurizing and Leak-Checking Every Joint Before You Trust It

Do not call the job done until it has held water under pressure. Pull the aerator off the end of the spout first so any debris loosened during the work can flush out instead of clogging the screen. Then slowly reopen the angle stops, one at a time, while you watch and feel every connection you made.

Run a dry hand or a paper towel around each joint: both angle stops, both faucet connections, and the base of the faucet on top of the sink. A compression joint that drips usually needs a small additional turn, not a full crank. Let the faucet run hot and cold for a minute, then shut it off and check again, because some slow weeps only show after the line has been under steady pressure for a few minutes. Look underneath one more time after the first full day of normal use. Reinstall the aerator once the water runs clear. A faucet that stays dry top and bottom through a day of use is one you can stop thinking about.

Frequently Asked Questions

How do I know if my sink takes a centerset or a widespread faucet?
Count the holes and measure center to center between the two outermost ones. Three holes about four inches apart take a centerset; three holes about eight inches apart take a widespread. A single-hole faucet with a deck plate can usually cover a three-hole sink.

Do I need plumber’s putty under the new faucet?
Only if the manufacturer calls for it. Many new faucets include a gasket and are designed to seal dry, and adding putty can interfere with that fit. Follow the instructions for your specific model.

Should I use thread tape on the supply line connections?
Not on compression fittings, which is what most supply lines and shutoff valves use. They seal by compressing a ring, and tape on those threads can cause a leak. Use PTFE thread tape only on tapered male threaded joints.

Can I reuse the old supply lines?
It is better not to. New braided supply lines cost little, and old lines may have been kinked or weakened during removal. Fresh lines reduce the chance of a leak you will have to revisit.

How tight should the mounting nuts be?
Tight enough that the faucet will not slide or spin on the deck, and no tighter. Many mounting nuts are plastic and will strip or crack if overtightened. Firm and immovable is the goal.

This article is general information, not professional advice. A standard deck-mounted faucet swap with the supply stops closed is well within do-it-yourself range, but if a shutoff valve will not close, if the connections are not the compression or threaded types described here, or if you uncover in-wall or supply-side problems, have a licensed plumber take a look.

Sources

  • U.S. EPA, WaterSense, Bathroom Faucets: https://www.epa.gov/watersense/bathroom-faucets
  • U.S. Department of Energy, Federal Energy Management Program, Best Management Practice #7: Faucets and Showerheads: https://www.energy.gov/cmei/femp/best-management-practice-7-faucets-and-showerheads
  • U.S. EPA, How Does the Safe Drinking Water Act Limit Lead in Pipes, Plumbing Fittings, Fixtures, Faucets, Solder and Flux: https://www.epa.gov/lead/how-does-safe-drinking-water-act-limit-lead-pipes-plumbing-fittings-fixtures-faucets-solder
  • U.S. EPA, Compliance Advisory: Manufacturers and Importers May Be Liable for Plumbing Products Not Certified as “Lead Free”: https://www.epa.gov/enforcement/compliance-advisory-manufacturers-and-importers-may-be-liable-plumbing-products-not

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