To fix a leaking bathroom sink faucet, start by shutting off the water supply and identifying the faucet type. In most cases, you can stop the drip by replacing a worn washer, O-ring, or cartridge and then reassembling the faucet. This guide covers common causes, tools, step-by-step repair instructions, and signs that you need professional leak detection help.
What Causes a Bathroom Sink Faucet to Leak?
Bathroom faucets leak for several reasons. The most common cause is a worn internal rubber part, such as a washer or O-ring. Constant pressure and movement cause these seals to lose flexibility. A damaged cartridge, loose packing nut, corroded valve seat, or debris in the water lines can also create a steady drip. Knowing the source helps you choose the right repair.
According to the EPA WaterSense program, even a small household leak can waste water over time, so fixing it quickly is a smart move. If you are not sure where the water is coming from, check under the sink first. A leaking supply line or drain trap can look like a faucet leak but may actually be a pipe issue. In that case, you may need pipe repair instead of a basic faucet repair.
Identify the Faucet Type and Leak Point
Before buying replacement parts, identify the type of faucet in your bathroom. The repair method depends on whether you have a compression, ball, cartridge, or ceramic-disc faucet. The table below is a starting point.
| Faucet Type | Common Leak Location | Typical Cause |
|---|---|---|
| Compression | Handle or spout | Worn seat washer or O-ring |
| Ball | Handle or spout | Worn ball valve or springs |
| Cartridge | Handle or spout | Failed cartridge or loose retaining clip |
| Ceramic disc | Handle base | Damaged ceramic discs or inlet seal |
The exact parts vary by manufacturer, so take the old stem or cartridge to a hardware store to match it. If you need help locating shutoff valves or testing the supply lines, consider a professional leak detection visit.
Tools and Materials You May Need
- Adjustable wrench or basin wrench
- Screwdrivers: flat-head and Phillips
- Replacement washers, O-rings, or cartridge for your faucet
- Silicone faucet grease
- Thread seal tape (plumber's tape)
- Small bucket, towels, and work gloves
- Flashlight for seeing under the sink
Most bathroom sink faucets use common tools. If you do not have the right replacement part, turn off the water and wait until you can match the old part. Never force a cartridge or stem; that can damage the valve body.
Step-by-Step: How to Fix a Leaking Bathroom Sink Faucet
Step 1: Shut Off the Water Supply
Locate the shutoff valves under the sink and turn them clockwise until they stop. Then open the faucet handle to release remaining water and pressure. If the valves are hard to turn, use pliers with a cloth. If the valves are missing or damaged, turn off the main water supply for your home. While the water is off, it is a good time to inspect the supply lines for corrosion or leaks. You may also want to handle any toilet repair tasks in the same bathroom.
Step 2: Remove the Handle
Use a screwdriver to remove the handle screw. The screw is often hidden under a decorative cap on the handle. Pry the cap off gently, then pull the handle straight off. If the handle is stuck, wrap it in a cloth and wiggle it gently to avoid scratching the finish. For ball- and cartridge-type faucets, the handle may have a small set screw on the side. Set all screws aside in a safe place.
Step 3: Remove the Bonnet or Retaining Nut
After the handle is off, you will see the bonnet or retaining nut that holds the valve mechanism in place. Use an adjustable wrench to loosen it. For a compression faucet, this exposes the stem assembly. For a cartridge faucet, you may need to pull a retaining clip before lifting the cartridge. Keep the parts in order; laying them out on a towel can make reassembly easier.
Step 4: Replace the Worn Washer, O-Ring, or Cartridge
Look for the worn part that is causing the leak. In a compression faucet, inspect the seat washer at the base of the stem. If it is flattened or cracked, replace it with the same size and type. If the valve seat is rough, replace it or use a seat-dressing tool. In a cartridge faucet, replace the entire cartridge if the old one feels stiff or cracked. In a ceramic-disc faucet, inspect the inlet seals and ceramic discs; handle the discs carefully because they can chip.
Lubricate new rubber parts with silicone faucet grease before installing them. Use thread seal tape on threaded connections only where the manufacturer specifies it. Do not over-tighten plastic or brass parts because the body can crack.
Step 5: Reassemble and Test the Faucet
Put the stem or cartridge back into the faucet body, tighten the retaining nut, and reattach the handle. Turn the water supply back on by opening the shutoff valves counterclockwise. Let the water run for a few seconds, then turn the handle off and check for drips at the spout and base. Wipe the area dry and check under the sink for moisture.
If the leak is around the handle, tighten the packing nut slightly. If water still drips from the spout, you may need to repeat the process or call a professional. Remember that plumbing installations should follow current codes, such as those developed by the International Association of Plumbing and Mechanical Officials (IAPMO).
Step 6: Check Under the Sink and Around the Base
After testing, dry the area under the sink and check again in a few hours. A small amount of moisture can reveal a loose supply nut or a leaking drain flange. Tighten fittings gently. If you notice mineral buildup around the faucet base, clean it and watch for recurrence. For related slow-draining problems, see our drain cleaning guide. If water stains appear on the cabinet floor, call a plumber because the leak may be inside the wall or supply line.
When to Call a Professional
Some faucet repairs are straightforward, but other issues require expert help. If you have low water pressure, multiple leaks, or a faucet that still drips after new seals, call a plumber. Corroded valves, stripped threads, and hidden wall leaks are not good DIY jobs. A professional can also inspect related systems, such as drain cleaning for a slow sink, water heater repair for uneven hot water pressure, or sewer line repair for draining backups.
If the leaking faucet drips hot water only, you may also want to review your water heating setup for efficiency. The Department of Energy's water heating tips can help you save energy after the drip is fixed. A small leak can lead to bigger problems over time, so do not ignore it.
Preventing Future Bathroom Faucet Leaks
Keep the faucet area clean and avoid hanging heavy items from the handle. Turn faucet handles off gently, not with excessive force. Check under the sink regularly for moisture or mineral buildup. If your water pressure is very high, consider a pressure-reducing valve or consult a plumber; high pressure can stress washers and cartridges. If you have hard water, routine cleaning of the aerator and cartridge can reduce mineral deposits.
Need a little backup? Contact MyTownPlumber for professional faucet repair and other home plumbing services. Our team can handle everything from small drips to larger plumbing emergencies. Use our plumbing offer to schedule service and get your bathroom back in working order.