How to fix a leaky bathroom sink faucet

Dry the vanity, put a sheet of paper towel under the faucet and drain, run the water, and watch where the paper gets wet first. A spout that drips is blaming a cartridge or washer. A wet handle collar suggests an O-ring or a bonnet that has worked loose. Moisture at the base implicates the faucet's own gasket. Drops under the basin point to a supply hose, a shutoff or the drain. For the wider picture of fixtures in kitchens and baths, see the faucet, sink, shower and disposal overview.

Which of the five spots is actually leaking?

The paper-towel trick answers this. Wipe every surface dry, lay paper under the faucet, handle and pipes, and turn the water on for a minute. Whichever sheet darkens first marks the source. A drip that only happens with the water running points to the faucet body, while one that continues when it is off points to the cartridge.

Check five zones, in this order:

• Spout tip: if it drips while the handle is closed, a worn cartridge, washer or seat is the cause.
• Handle: dampness seeping out under the handle usually traces to an O-ring that has split or a bonnet nut that has backed off.
• Faucet base: a ring of water on the deck suggests a tired gasket or a mounting nut that needs snugging from beneath.
• Supply hoses and stop valves: a wet connection inside the vanity.
• Pop-up drain and trap: water that only appears after the basin has been filled and emptied.

What repairs a dripping spout or a weeping handle?

Turn off both small stop valves beneath the basin, then run the faucet until the flow dies. Start at the handle: pop off its decorative cap, back out the screw hiding there and lift the handle away. Under it sits the bonnet, which unscrews to free the cartridge or stem. Install a matching washer, ring or whole cartridge, coat the rubber lightly with grease, and reassemble the parts in the opposite sequence.

A cartridge from one maker will not fit another's faucet. Take the worn part along when you shop, or jot down the brand and model marked on the faucet body. Photos at each step make reassembly easy. With two handles, the weak point is typically the rubber washer on the stem tip, and the brass seat it presses against may be pitted. Light pitting can be dressed flat with a seat tool, otherwise the faucet is done. A single lever almost always means a new cartridge, or the kit made for that model.

What if the puddle is at the faucet base or inside the vanity?

Around the base, suspect a loose mounting nut beneath the counter or a failed base gasket. Reach up with a basin wrench and snug the nut. Inside the cabinet, dry each connection one at a time and see which one gets wet first: a hose nut, a stop valve stem, the drain nut or the trap.

Supply hoses are cheap and fail with age, so replace a braided hose that is more than a decade old or shows rust. Hand-tighten a nut and add a quarter turn. Do not overtighten plastic nuts. If a shutoff drips around its stem, try a slight turn on the packing nut. Still dripping means the valve needs replacing. For leaks on the pipes below the basin, see the guide on leaking pipes under a sink.

Why does the pop-up drain leak?

The pop-up drain assembly has a rubber or plastic gasket under the sink flange and a pivot rod seal. When either hardens, water seeps out each time the basin drains. Begin by tightening the pivot rod nut. When the seep continues, fit a fresh gasket or a whole new drain assembly, seated in plumber's putty or its supplied gasket.

This is the leak people mistake for a faucet leak, because it only shows after you fill and empty the sink. If the stopper does not hold water or the lift rod is stiff, clean and adjust it. To see how the stopper lifts out, read about clearing a clogged bathroom sink.

Should I repair the faucet or replace it?

Fixing the old one is sensible when it is under ten years old, the finish is sound and parts are still on sale. Go with a new faucet when the finish has pitted, the body rocks, replacement parts are gone from shelves, or this would be the second repair. A new faucet can use less water, and a WaterSense-labeled one is rated for 1.5 gallons a minute or less.

Bathroom faucets with a WaterSense label can cut water use without changing how they feel, a point the EPA makes in its leak guidance. Santa Monica homes with older vanity fixtures often have brass that scales up in hard water, and a replacement may be the cleaner fix. A typical price range is on the page about faucet installation cost.

Is it a job for a plumber?

Bring one in when the stop valve is seized, water is getting out inside the wall, the faucet is obsolete, the cabinet is already damaged, or you would rather not lie under a vanity. Water that reaches the cabinet floor for weeks can swell wood and grow mold, so deal with any wetness promptly.

A lone faucet swap sits far below the thousand-dollar line where California's contractor licensing rule begins, deposit limits included. Ready to book? The quote page takes it from here, and the full service list shows what else is available.

Common questions

What is a realistic time estimate?

A cartridge or washer swap runs thirty to sixty minutes, a supply hose about fifteen, and a pop-up drain assembly up to an hour. Leave room for a second store run if the first part is wrong, and for letting the cabinet dry out before closing it up.

Why does it drip only on the hot side?

A hot-side seal or cartridge has worn, or mineral scale is holding it open. If your faucet has two handles, replace the hot side washer and check the seat. In a single-lever faucet, the cartridge is the part to replace.

Which tools does this job call for?

Most jobs need an adjustable wrench, a basin wrench, pliers, a small screwdriver set, hex keys, plumber's grease and a bucket. A headlamp or flashlight helps in the dark space under the vanity, and your phone camera records each step for reassembly.

Is a slow drip really worth fixing?

Yes. According to the EPA, an average home wastes over 9,300 gallons in a year through leaks, and one faucet dripping steadily can supply thousands of them, so the bill rises. Staining in the basin and extra wear on the fixture follow as well.