Of all the plumbing jobs in a house, replacing a bathroom faucet is one of the kindest to beginners. The connections are visible, the water pressure is off before you start, and nothing is hidden inside a wall. The genuinely hard part isn't plumbing. It's working on your back, under a sink, reaching up into a space designed by someone who never had to reach into it.
Faucets are sold by how the holes in your sink are spaced, and buying the wrong spread is the mistake that stops this job before it starts. Look at your current setup and measure between the hot and cold handles.
| Type | Hole pattern | How to spot it |
|---|---|---|
| Centerset | 3 holes, 4 inches apart | Spout and handles on one base, or three pieces close together |
| Widespread | 3 holes, 8 to 16 inches apart | Separate handles mounted in the sink or counter, away from the spout |
| Single-hole | 1 hole (sometimes a cover plate over 3) | One post with a lever; a deck plate may hide a 4-inch spread |
Count the holes while you're under there too — some sinks have the holes in the countertop instead of the sink itself, and pedestal sinks can make the rear nuts miserable to reach. Match the new faucet to what's drilled, not to what you wish was drilled.
Shut the water off and drain the lines. Close both shutoff valves under the sink (clockwise). Open the faucet and let it run dry. If a valve won't fully close or drips steadily, shut off the house main instead — don't start the job against live water.
Disconnect the supply lines. Bucket under the valves, towels down. Loosen the supply line nuts at the shutoffs and let the lines drain into the bucket. Take a phone photo of the whole setup first — it settles every "which side was hot?" question later.
Unbolt and lift out the old faucet. From underneath, loosen the mounting nuts or bracket holding the faucet to the sink. This is where the basin wrench earns its keep. Old nuts may be corroded — patience and penetrating oil beat force. Lift the faucet out from above.
Clean the deck completely. Scrape off every trace of old putty and caulk with a plastic scraper, then wipe with rubbing alcohol. New sealant on top of old crud is a leak with a head start. This five-minute step decides how the job looks in a year.
Seal the base — putty or silicone, by surface. Roll plumber's putty into a thin rope and press it under the faucet base or gasket if the maker calls for it: it's the traditional choice and cleans up easily. But never use putty on marble, granite, or other natural stone — its oils stain stone permanently — and some plastic sinks rule it out too. On stone and those plastics, use silicone sealant instead. The full reasoning is in our comparison of plumber's putty vs silicone caulk.
Set and tighten the new faucet. Lower it into the holes, line it up straight from above, then tighten the mounting hardware from below — snug and even, alternating sides. Check alignment from the front before the final snug. Overtightening cracks sink decks and distorts gaskets.
Connect the supply lines. Attach the hot and cold lines to the correct shutoffs. Hand-tight, then about a quarter turn more with the wrench. Compression fittings seal on the ferrule, not on brute force — a cranked nut is a common cause of the slow drip people blame on the faucet.
Install the pop-up drain, if included. Unscrew the old drain flange from above and the trap connection below. Set the new flange with putty (or silicone on stone), thread the drain body on, and connect the pivot rod to the lift rod so the stopper rises and seals evenly. Reconnect the trap.
Flush, then check for leaks. Remove the aerator from the spout, turn the water back on, and run both hot and cold for about 30 seconds to flush out debris. Reinstall the aerator. Then run your fingers around every connection you touched, and look with the flashlight. A dry paper towel wiped under each joint shows a slow leak your fingers might miss.
Skipping the measurement. A widespread faucet cannot squeeze into a 4-inch centerset sink. Measure the handle spread and count the holes before the old faucet comes out — or before you even buy.
Reusing tired supply lines. Old rubber-washer lines are cheap to replace and a classic source of slow leaks. If the new faucet doesn't include lines, new braided stainless ones cost little and last far longer.
Putty on stone. It bears repeating because the stain is permanent: plumber's putty and natural stone do not mix. Silicone exists for this.
Packing everything back under the sink immediately. Give the connections a day of observation before the cleaning supplies move back in.
Measure the spread, shut the water off, work patiently from underneath, and let the sealant choice follow your sink material. Do that and a bathroom faucet swap is a tidy Saturday job. The same shutoff-and-supply-line skills transfer directly if you later tackle a kitchen faucet install, and if your old faucet's problem was a drip rather than its looks, our walkthrough to fix a leaky faucet covers the repair route for under $20 in parts.
Either can seal the base — the sink decides. Plumber's putty is standard on vitreous china and most metal-deck sinks. On marble, granite, or other natural stone, use silicone: putty oils permanently stain stone. Check the faucet manual too; some models use a foam gasket and want no sealant at all.
Plan on 1 to 2 hours the first time, most of it spent removing the old faucet and cleaning the deck. A straightforward swap with cooperative hardware can take 45 minutes. Corroded mounting nuts are the usual time thief.
You can, but you shouldn't if they're old rubber-washer lines. They're a leading cause of slow under-sink leaks, and a new faucet deserves new lines. Braided stainless lines are inexpensive insurance.
Only if the new faucet comes with a pop-up drain — mixing a new faucet with an old, corroded drain flange looks mismatched and the old lift mechanism may not match. If the new faucet has no drain assembly, your existing pop-up can usually stay.
Almost always a supply connection: a nut that's a quarter turn short of sealed, a cocked washer, or an old line reused past its life. Dry everything, run the water, and find the highest wet point — water runs down, so the leak is at or above where you see it.