Install a Bathroom Faucet

Bathroom faucets wear out. Seals fail, finishes corrode, handles strip. A new faucet transforms a sink from shabby to sharp in an afternoon. The work happens mostly under the sink in tight quarters with a flashlight clenched in your teeth, but the job is straightforward: disconnect the old, connect the new, check for leaks. The difference between a clean installation and a frustrating one comes down to preparation—knowing your sink configuration, having the right basin wrench, and taking ten extra minutes to clean the mounting surface properly. A well-installed faucet should give you a decade of service without drips or wobble.

1. Shut off water and drain the lines. Turn the shutoff valves under the sink clockwise until tight. Turn the faucet handles to hot and cold to release pressure and drain remaining water from the lines. Place a bucket under the supply lines to catch residual drips.
2. Disconnect supply lines and remove old faucet. Use a basin wrench to loosen the nuts connecting supply lines to the faucet tailpieces. Remove the mounting nuts holding the faucet to the sink—these thread onto tailpieces from below. Lift the old faucet straight up and out. If it's stuck with old putty or caulk, gently work a putty knife around the base to break the seal.
3. Clean the mounting surface. Scrape away old plumber's putty, caulk, or mineral deposits from the sink deck with a plastic scraper. Wipe the area clean with rubbing alcohol and a rag. The surface needs to be completely smooth and dry for a proper seal.
4. Install the gasket and position the new faucet. Place the rubber gasket or deck plate onto the mounting holes. If your faucet requires plumber's putty instead, roll a rope of putty and press it around the base of the faucet. Set the faucet into position, feeding tailpieces and supply lines through the mounting holes. Make sure it's centered and aligned before moving to the next step.
5. Secure mounting hardware from below. Climb under the sink and thread mounting nuts onto the faucet tailpieces by hand. Use a basin wrench to snug them firmly, alternating between nuts to keep pressure even. Check alignment from above, adjust if needed, then give each nut a final quarter turn.
6. Connect supply lines to faucet. Attach flexible supply lines to the faucet tailpieces—hot to the left side, cold to the right. Hand-tighten first, then use an adjustable wrench to turn each connection one more full turn. Don't force it; you're compressing a washer, not welding steel.
7. Connect supply lines to shutoff valves. Attach the other end of each supply line to the corresponding shutoff valve under the sink. Hand-tighten, then snug with a wrench. Don't overtighten—these compression fittings seal with a rubber washer, not muscle.
8. Test for leaks and finish up. Turn the shutoff valves back on slowly and watch for leaks at both connection points. Turn the faucet on—hot and cold—and let water run for two minutes while checking all connections. Wipe away any water and watch for new drips. If dry, you're done. If not, snug the leaking connection another quarter turn and retest.