How to Fix a Bathroom Sink Faucet | DIY Fix, Save $450

Fix a leaking bathroom sink faucet by shutting off water, removing handle and cartridge, replacing worn washers or O‑rings, then testing.

A dripping bathroom sink faucet can cost you $150 to $300 in plumber fees — or about $8 in parts and an hour of your time. Knowing how to fix a bathroom sink faucet starts with the right diagnosis and a few basic tools. This guide covers both repairing a leaky faucet and replacing the whole unit if it’s beyond saving, so you can decide which route makes sense and get it done without a second trip to the hardware store.

What Tools and Parts Do You Need?

Most faucet repairs use the same short list of tools. Gather these before you start so you don’t have to stop mid-job to find a basin wrench.

Identify Your Faucet Type Before You Start

Not all faucets come apart the same way. Knowing what you’re working with determines which replacement parts to buy and which steps to follow.

Centerset faucets are the most common type in US bathrooms — the spout and handles sit on a single base plate with three holes. Single-handle faucets use one cartridge that controls both hot and cold flow. Two-handle faucets have a separate cartridge or stem for each handle. Washer-less (quarter-turn) faucets use a cartridge with a rubber seat and spring rather than a traditional rubber washer. Check the brand name on the handle or escutcheon, then look up the exact cartridge model online — Delta, Pfister, and Moen all make parts easy to find through their support pages.

Repairing a Leaky Bathroom Sink Faucet: Where Leaks Actually Start

Most leaks come from three places: a worn rubber washer at the stem base, a cracked O-ring on the cartridge, or mineral deposits inside the cartridge that prevent a clean seal. Fixing any of them follows the same sequence.

1. Turn off the water. Close the shutoff valves under the sink — both hot and cold. Open the faucet handle to drain remaining pressure.
2. Remove the handle. Pry off the decorative cap (hot/cold indicator) with a small screwdriver. Unscrew the handle screw and lift the handle off.
3. Take a photo of the cartridge orientation. This one step prevents reassembly errors. The cartridge fits only one way.
4. Remove the retaining clip or bonnet nut. Pull the cartridge straight out. If it’s stuck, use a cartridge puller instead of prying with a screwdriver — prying can crack the valve body.
5. Inspect and replace worn parts. Check the rubber washer, O-rings, and seals. If the cartridge itself is cracked or corroded, replace the whole cartridge. For washer-less faucets, also check the rubber seat and spring underneath.
6. Lubricate new seals with plumber’s silicone grease before installation.
7. Reassemble in reverse order. Match the cartridge orientation to your photo, reinstall the clip or nut, put the handle back on, and turn the water on slowly.
8. Test for leaks. Run the water for 2–3 minutes and check under the sink and around the handle base. If it still drips, you may need to replace the seat or spring. Everstein’s full repair guide covers the extra steps for stubborn leaks.

How to Replace an Entire Bathroom Sink Faucet

If the faucet body is cracked, heavily corroded, or you just want an upgrade, full replacement is the answer. A new centerset faucet runs $50–$150 for a solid unit.

1. Prep the area. Turn off the water supply. Clear everything out from under the sink and place a bucket underneath to catch drips.
2. Disconnect the supply lines with an adjustable wrench. Then use a basin wrench to loosen and remove the mounting nuts that hold the faucet to the counter.
3. Lift the old faucet out from above. Be careful not to damage the sink surface or the tubing.
4. Install the new faucet. Add the rubber gasket (or a thin bead of plumber’s putty if the manual calls for it) to the base. Insert the supply lines through the mounting holes and center the faucet. Tighten the mounting nuts from below with the basin wrench.
5. Reconnect the supply lines — hot to hot, cold to cold. Hand-tighten plus a quarter turn with the wrench; overtightening can crack the plastic nuts.
6. Flush and test. Turn the water back on and let it run for one full minute to clear any debris from the new lines. Check every connection for drips. If you removed the aerator earlier, replace it now.

If you’re shopping for a replacement and want to compare top-rated models, our tested roundup of the best bathroom sink faucets breaks down what actually holds up over time.

Common Mistakes That Cause Leaks to Come Back

Even with the right steps, a few small errors can undo your work. Skip these and your repair will last.

• Skipping the orientation photo. Putting a cartridge in backward forces the handle to behave opposite of what you expect and can damage the valve.
• Over-tightening connections. Supply line nuts and mounting nuts only need to be snug — too much force cracks gaskets and creates new leaks.
• Ignoring the aerator. A low-flow problem after repair usually means mineral scale in the aerator. Soak it in white vinegar for 20 minutes and scrub clean.
• Buying the wrong cartridge. Delta, Pfister, and Moen cartridges are not interchangeable. Check the brand and model before ordering.
• Not flushing the system. Debris from new supply lines can lodge in the cartridge and cause a drip. Always run the water a full minute after reassembly.

When Should You Call a Pro Instead?

You can handle most leak repairs yourself with basic tools. Call a plumber if the shutoff valves under the sink are seized and you can’t turn off the water, if the faucet is more than 15 years old and parts are no longer available, or if you’ve replaced the cartridge and the leak persists. Professional installation runs $150–$300, so the DIY savings are real — but a repair that doesn’t actually fix the problem costs you time and water.

Fix-It-at-a-Glance Checklist

Whether you’re repairing or replacing, these five reminders keep the job smooth. Shut off both water valves before touching anything. Photograph the cartridge orientation before removal. Lubricate every new seal with silicone grease. Never overtighten — snug is enough. And always flush the system for one minute before calling it done. A leak-free faucet on the first try beats a second trip under the sink.