How to Install a New Bathroom Faucet

Replacing a bathroom faucet is one of the most satisfying plumbing projects you can do yourself. It takes about an hour, requires only basic tools, and transforms the look of your entire bathroom. A new faucet isn't just cosmetic—it stops drips that waste water, gives you better water pressure, and replaces worn-out handles that have been sticking for years. The work happens in two zones: above the sink (removing and installing the faucet body) and below it (disconnecting and reconnecting supply lines). If your old faucet is corroded or you're working in a tight under-sink space, it can feel awkward, but there's no structural complexity here. The real key is shutting off the water first, having a bucket ready to catch spillage, and taking time to hand-tighten everything before you grab a wrench.

1. Turn off the water supply. Locate the shutoff valves under the sink—they're usually oval knobs on the hot and cold supply lines coming from the wall. Turn both clockwise until they stop. If you can't find them or they don't work, shut off the main water supply to the house. Open the faucet to bleed residual pressure and confirm the water is off.
2. Disconnect the old supply lines. Position your bucket under the connections. Using an adjustable wrench, hold the fitting body steady with one wrench while turning the nut counterclockwise with another. Do this for both hot and cold lines. If the nuts are corroded and won't budge, spray them with penetrating oil and wait 15 minutes. Once disconnected, you can set the supply lines aside or let them drain into the bucket.
3. Remove the old faucet body. From underneath the sink, locate the mounting nuts holding the faucet to the sink deck. These are usually large nuts screwed onto bolts that come down through the sink. Use an adjustable wrench or basin wrench (a specialized tool with a crank handle that grips the nut in tight spaces) to turn these counterclockwise. With both nuts loose, push the old faucet up and out from the top. Clean away old caulk or putty with a plastic scraper.
4. Prepare the sink deck. If your new faucet uses the same holes as the old one, you're done. If not, fill old holes with marine epoxy putty, smooth it level with the sink surface, and let it cure per the product instructions (usually 5–10 minutes). If the sink has a single large hole and your new faucet has a single mounting post, the hole is ready to go. Wipe the entire deck clean of debris.
5. Install the new faucet. Place the rubber gasket and mounting hardware that came with your faucet in the correct order (the manual will show this). Position the faucet body so the spout faces the way you want it and the mounting bolts thread down through the sink deck. From underneath, hand-tighten the mounting nuts first—don't use a wrench yet. Once hand-tight, use your wrench to snug them down firmly, but don't over-torque or you'll crack the sink. The faucet should sit flush against the deck with no rocking.
6. Connect the new supply lines. Identify the inlet ports on the new faucet—they're usually labeled H (hot) and C (cold). Screw the supply line nuts onto these ports by hand first, making sure you have the hot line on the hot port. Then use two wrenches to tighten the connections: one to hold the fitting body and one to turn the nut clockwise. Snug them firmly but don't over-tighten. Apply plumber's thread seal tape to supply line threads if they're not pre-sealed.
7. Test for leaks and adjust. Turn the shutoff valves back on slowly—give the lines 30 seconds to fill. Check all three connection points (hot supply, cold supply, and spout) for drips while the faucet is running at full pressure. If you see a leak at a supply line connection, tighten it one more quarter-turn with your wrench. If water is dripping from the faucet spout itself after you close it, most new faucets have a small adjustment screw under the handle; tighten it slightly. Let it run for a minute to clear air from the lines.
8. Clean up and caulk (optional). Wipe away any dust or debris from under the sink. If your sink has a gap between the faucet body and the deck, and your faucet doesn't come with a base plate, run a bead of silicone caulk around the base and smooth it with a caulk tool or wet finger. This keeps water from seeping between the faucet and the sink material. It's not always necessary, but it looks finished and protects against water damage in the deck.