Bathroom Sink Faucet Leaking? How to Diagnose and Fix the Leak

A leaking bathroom sink faucet can come from the spout, the base of the swivel spout, the handle, the cartridge, or a connection underneath the sink. The leak location is more useful than the faucet brand or age when deciding which part to inspect.

Shut off the water before disassembly, dry the faucet, and identify the first point where moisture returns. Stop DIY work if the shutoff valves will not close, the faucet body is cracked, a supply line is actively leaking, or parts are seized.

Start With Safety

1. Close the hot and cold shutoff valves under the sink.
2. Open the faucet to release pressure.
3. If either shutoff valve fails, turn off the main water supply.
4. Put a towel and small bucket below the plumbing.
5. Take photos before removing parts.
6. Never force a corroded nut or cartridge.

If water is spraying, reaching an electrical outlet, or coming from inside the wall, stop and call a licensed plumber.

Locate the Leak With a Dry Test

1. Dry the faucet, handles, spout, supply lines, and cabinet floor.
2. Turn the water back on.
3. Run the faucet and move the handle through hot and cold.
4. Swivel the spout from side to side.
5. Turn the faucet off and watch for the first bead of moisture.
6. Check under the sink with a flashlight and paper towel.

Common Leak Symptoms

Identify the Faucet Type

Cartridge faucet

Common on single-handle faucets. The handle usually sits over a cartridge held by a clip, nut, or retainer.

Ceramic disc faucet

Uses a cartridge with two ceramic discs. The handle often moves smoothly, and the complete cartridge is commonly replaced.

Ball faucet

Uses a ball, cam, springs, and seats. It is common on older single-handle designs.

Compression faucet

Uses separate hot and cold handles and a rubber washer pressed against a valve seat.

If the model is unknown, find the brand or model number on the faucet body or supply tag. Compare the old part directly when possible.

Tools and Parts

• Adjustable wrench
• Allen keys
• Phillips and flat-head screwdrivers
• Needle-nose pliers
• Small pick for O-rings
• Flashlight or headlamp
• Bucket and towels
• Replacement cartridge, washer, O-rings, seats, or springs
• Plumbing-safe silicone grease when recommended

Use manufacturer parts for cartridges and complex seals. A part that looks similar may have different ports, dimensions, or sealing surfaces.

Repair the Spout Drip

Cartridge faucet

1. Shut off the water and remove the handle.
2. Remove the retaining clip, nut, or trim.
3. Pull the cartridge straight out.
4. Clean mineral buildup without scratching the cavity.
5. Install the correct replacement cartridge in the same orientation.
6. Reassemble and test.

Ceramic disc faucet

1. Remove the handle and trim.
2. Remove the retaining nut or screws.
3. Pull out the ceramic cartridge.
4. Replace the complete cartridge unless the manufacturer permits replacing only inlet seals.
5. Reassemble and open the water slowly.

Ball faucet

1. Remove the handle, cap, cam, washer, and ball.
2. Replace the springs and seats.
3. Install them in the correct orientation.
4. Reassemble and test.

Compression faucet

1. Remove the handle and stem.
2. Replace the seat washer and inspect the stem O-ring.
3. Check the valve seat for pitting.
4. Resurface or replace the seat when required.
5. Reassemble and test.

Repair a Leak Around the Spout Base

Water around the swivel-spout base commonly indicates worn O-rings.

1. Shut off the water.
2. Remove the handle and any spout retaining parts.
3. Lift the spout according to the manufacturer’s instructions.
4. Remove the old O-rings without scratching the grooves.
5. Clean mineral deposits.
6. Lubricate and install the exact replacement O-rings when recommended.
7. Reassemble and test with the spout in several positions.

If the spout or faucet body is cracked, replacement is usually required.

Repair a Leak Around the Handle

1. Confirm the leak is not running down from the spout.
2. Shut off the water and remove the handle.
3. Inspect the cartridge, handle O-ring, and retaining nut.
4. Replace damaged seals or the cartridge.
5. Snug a loose packing nut without overtightening.
6. Test the handle through hot, cold, and both extremes.

Check Under-Sink Connections

1. Dry every supply and drain connection.
2. Run water and watch for the first damp point.
3. Tighten a loose compression nut slightly while holding the fitting steady.
4. Do not overtighten a compression fitting.
5. Replace a cracked supply line, damaged ferrule, or stripped nut.
6. Check the pop-up drain and P-trap separately by filling and draining the sink.

If the leak is coming from inside the wall or a shutoff valve will not close, stop and call a plumber.

Test the Repair

1. Open the shutoff valves slowly.
2. Leave the faucet open to release trapped air.
3. Test hot, cold, on, off, and swivel positions.
4. Fill the sink and check the drain assembly.
5. Dry all connections and wait several minutes.
6. Check the cabinet again after normal use.

Repair or Replace?

Repair is usually reasonable when:

• The faucet body and finish are in good condition.
• The correct cartridge or seal is available.
• The leak comes from a replaceable wear part.
• This is the first major leak.

Replacement is usually more practical when:

• The faucet body or spout is cracked.
• Corrosion or pitting is extensive.
• Fasteners or threads are stripped.
• The model is discontinued and parts are unavailable.
• Leaks return after correct repairs.

When to Stop DIY Work

Call a licensed plumber when:

• A shutoff valve will not close.
• A supply pipe or drain leaks inside the wall or floor.
• A fitting is seized, stripped, or heavily corroded.
• The faucet body is cracked.
• Water is leaking from several locations at once.
• The cabinet has mold or structural water damage.
• The repair requires opening the wall.

Prevent Another Leak

• Clean the aerator when flow becomes uneven.
• Wipe the finish with a soft cloth and mild soap.
• Address hard-water buildup before it reaches seals.
• Check under the sink for moisture several times a year.
• Replace stiff or cracked supply lines before they fail.
• Keep the faucet mounting hardware secure.
• Use the correct replacement parts for the model.

Frequently Asked Questions

Why does the faucet drip after it is turned off?

The cartridge, washer, ball seats, or valve seat is not sealing completely. Identify the faucet type before buying parts.

Why is water around the base of the spout?

The swivel-spout O-rings are a common cause. A loose mounting base or cracked spout can also produce moisture in the same area.

Can I replace only the O-rings?

Sometimes. If the O-rings are replaceable wear parts and the spout and body are undamaged, replacing them may solve the leak.

Why does the faucet still leak after a cartridge replacement?

The part may be incorrect, installed in the wrong orientation, contaminated by debris, or the valve body may be damaged.

Is a leaking faucet always a DIY repair?

No. Simple cartridge, washer, and O-ring repairs are often manageable. Leaks from concealed plumbing, seized valves, or cracked fixtures require professional service.

Final Takeaway

Find the leak location first, then match the repair to the faucet mechanism. Shut off the water, use the exact replacement parts, and test the faucet through every operating position before reassembling the trim.

If the faucet body is damaged, the plumbing is concealed, or the leak returns after the correct repair, stop DIY work and contact a licensed plumber.