How to Install a New Bathroom Sink Faucet

Replacing a bathroom faucet is one of the most satisfying plumbing projects a homeowner can do—it transforms how the sink looks and functions, costs less than a professional visit, and requires only basic hand tools. The work itself is straightforward: you're essentially removing old connections and making new ones with the same supply lines already in place. What matters is taking time to understand your sink's configuration before you start, getting the new faucet positioned correctly the first time, and making sure connections are tight enough to prevent leaks. A leaking faucet will cost you water and peace of mind, so this is one project where precision during assembly pays off immediately.

1. Isolate Your Water Source. Locate the shutoff valves under the sink—there should be two, one for hot and one for cold water. Turn both clockwise until they stop. If valves are stiff or missing, turn off the main water supply for the house. Turn on the faucet at the sink to release any remaining water pressure in the lines.
2. Free the Old Lines. Place a bucket under the connections to catch residual water. Using an adjustable wrench or basin wrench, loosen the compression nuts connecting the supply lines to the faucet tailpieces. Once hand-tight, unscrew completely and set the supply lines aside. If lines are corroded or difficult, apply penetrating oil and wait five minutes before trying again.
3. Detach the Drain Rod. If your faucet is connected to a popup drain system, you'll see a rod running from the faucet body down behind the drain pipe. Disconnect this rod from the faucet lever arm by loosening the clip or setscrew holding it in place. Some faucets have integrated drains and don't require this step.
4. Lift Out the Old Faucet. From underneath the sink, locate the mounting nuts holding the faucet body to the sink. These are usually large nuts at the base of each faucet tailpiece. Using a basin wrench or adjustable wrench, turn counterclockwise to loosen. You may need to hold the faucet steady from above with your other hand to prevent it from spinning. Once loose, push the old faucet up and out from the top of the sink. Remove and discard any rubber or metal washers and gaskets.
5. Clear the Mounting Surface. With the old faucet removed, use a damp cloth and a plastic scraper to clean away old caulk, mineral deposits, and debris from around the faucet holes. This gives the new faucet a clean surface to seal against and prevents old material from interfering with the new mounting.
6. Seat the Gasket First. Most new faucets come with a rubber gasket or silicone base plate designed to create a water-tight seal between the faucet body and sink. Place this gasket or plate over the sink holes first, ensuring it's centered and covers all penetrations. Then insert the faucet tailpieces through the holes from above. The gasket should sit flush against the sink surface with no gaps.
7. Lock Down Evenly. From underneath the sink, hand-thread the mounting nuts onto the tailpieces. Once hand-tight, use a basin wrench or adjustable wrench to tighten each nut in a cross pattern—tighten one side, then the opposite side, then repeat. This distributes pressure evenly and prevents the faucet from cocking to one side. Tighten until snug, but don't over-tighten, which can crack porcelain or crack the plastic tailpiece.
8. Attach the Water Lines. Take the original supply lines (or new ones, if replacing) and thread the compression nuts onto the faucet inlet ports. Hand-tighten first to ensure they're aligned, then use a wrench to tighten about three-quarters of a turn beyond finger-tight. Make sure the lines aren't kinked or pinched. Turn the shutoff valves back on slowly and check for drips at all connection points.
9. Restore Drain Function. If your faucet has an integrated popup drain, thread the drain rod back through the faucet lever arm and secure it with the clip or setscrew. The rod should move freely up and down. Test the lever arm and watch the drain rod move—it should rise and lower smoothly without binding. Make fine adjustments to the rod position if needed.
10. Verify No Leaks. Turn on the hot water supply valve, then the cold. Run water from the faucet for 30 seconds at full pressure, observing underneath the sink for any drips. Check both supply line connections and the drain area. Turn off the water and wait five minutes, then check again—a slow weep that stops is normal settling, but a steady drip means a connection needs tightening.
11. Seal the Edges. If water has seeped under the gasket or if you want a finished appearance, apply a thin bead of clear silicone caulk around the perimeter where the faucet base meets the sink. Smooth it with a wet finger and let it cure per the caulk manufacturer's instructions, usually 24 hours. Avoid using the faucet during cure time if possible.