How to Replace a Bathroom Faucet

Look at the deck of your existing sink (the flat ring of porcelain or metal around the bowl). Count the holes that the current faucet uses — 1, 3, or sometimes 4 if there is a side soap dispenser. For 3-hole sinks, measure center-to-center between the two outer holes: 4 inches means centerset (one combined faucet plate covers all three holes); 6 to 16 inches means widespread (three separate pieces — spout in the middle, hot and cold handles outboard). Single-handle faucets can cover a 3-hole sink with an included escutcheon plate, but a 3-hole faucet cannot bridge a single-hole sink.

Empty everything from under the sink — even items that seem out of the way. You will be on your back inside the cabinet for 20-40 minutes and every object becomes an elbow-bruising obstacle. Place a folded towel or knee pad on the cabinet floor. Reach behind the supply lines and turn both angle-stop valves clockwise until they stop, then turn on the old faucet to relieve pressure and confirm the water actually shut off — if water keeps trickling, go back and try the valves again or use the main shutoff.

Place a shallow pan or thick towels directly under the angle stops to catch the half-cup of water still in the lines. Use your basin wrench or adjustable wrench to unscrew the compression nuts where each supply line meets the angle-stop valve (counterclockwise — work the bottom connection first, then the top at the faucet). Behind the drain pipe, find the pop-up linkage — a thin metal rod that runs from a horizontal pivot at the back of the drain up through the faucet body. Loosen the small screw or clip holding it to the lift-strap and slide the rod free.

Lie on your back inside the cabinet with a headlamp on. Reach up to the underside of the sink — you will see one large plastic or brass nut on each faucet stud (single-handle: one nut; centerset: two nuts; widespread: three nuts). Hook the basin wrench's jaw onto each nut with the wrench shaft pointing away from the nut, then turn the shaft counterclockwise to loosen. If the nuts are corroded and will not turn after 30 seconds of effort, spray penetrating oil on the threads and walk away for 15 minutes — fighting a corroded nut barehanded is how DIY swaps turn into broken pipes.

With all mounting nuts off, climb out of the cabinet and lift the old faucet straight up off the sink. Underneath you will see a ring of old plumber's putty, dried silicone, mineral crust, or all three. Scrape it off with a plastic putty knife — never a metal blade on a porcelain or stone deck, which scratches the finish. Wipe the deck with a rag wet with white vinegar to dissolve the last mineral film, then dry it completely. A clean dry deck is the difference between a faucet that seals on the first try and one that weeps from underneath for the next year.

Unpack the new faucet and check whether it shipped with a rubber base gasket — most modern fixtures do. If yes, slide the gasket onto the underside of the faucet base and lower the faucet through the sink holes (gasket-only, no putty or silicone). If your faucet has no gasket, either roll a quarter-inch-thick rope of plumber's putty and press it in a continuous ring around the faucet base before setting it (for china or stainless sinks) or run a thin bead of 100% silicone caulk along the deck contact line (for stone or quartz). For widespread faucets, set the spout first, then the two handle valves, threading each through its own hole.

Back under the sink with the basin wrench. Hand-thread each mounting nut up onto its faucet stud as far as it will go by finger pressure alone (the gasket compresses easily — overtightening cracks porcelain or distorts the gasket). Then use the basin wrench to snug each nut down with about a quarter to a half turn past hand-tight. Resist the urge to crank — modern plastic nuts strip easily, and the gasket only needs gentle pressure to seal. Wiggle the faucet from above; it should feel solid with no rock or rotation.

Take the two NEW braided stainless supply lines you bought (do not reuse the old ones — the internal gaskets are deformed). Thread the smaller compression end (3/8-inch) onto the angle stop, hand-tight first, then a quarter turn past with a wrench. Thread the larger end (1/2-inch IPS) up onto the faucet inlet stud — hand-tight, then a quarter turn. The hot line always goes on the LEFT inlet (looking at the faucet from the front) and cold on the right; mixing them is a five-minute fix but it is annoying. PTFE tape is optional on these connections — the gaskets do the sealing — but a single wrap on the threads adds insurance.