Why Is My Faucet Leaking and How Do I Fix It?

Root cause

Compression faucets (two handles, one hot/one cold) seal with a rubber washer at the base of the stem. Over time it dries out, cracks, or gets pushed out of shape by mineral deposits, so it no longer seals against the valve seat — causing a steady drip from the spout.

30-second check

Turn off each handle's supply valve one at a time. If the drip stops when you shut off one specific side, that side's washer is worn.

Tools & materials

Adjustable wrench, screwdriver, replacement washer/O-ring kit matching your faucet brand, plumber's grease.

Step-by-step

1. 1 Shut off the water supply valves under the sink; open the faucet to drain the line.
2. 2 Pry off the decorative cap, remove the screw, and lift off the handle.
3. 3 Remove the retaining nut with pliers or a wrench to expose the stem.
4. 4 Unscrew the brass screw holding the washer at the bottom of the stem and swap in a new washer of the same size; check the stem O-ring too.
5. 5 Dab plumber's grease on the new O-ring, reassemble, and turn the water back on slowly.
6. 6 Run the faucet a few minutes and confirm the drip is gone.

Root cause

Single-handle and modern two-handle faucets use a cartridge, ball, or ceramic disc mechanism instead of a simple washer. Internal O-rings, seals, or springs inside these wear out with age and mineral exposure, causing drips at the spout or around the handle base.

30-second check

Wiggle the handle gently side to side with the water off — excess play, or a drip specifically when the handle sits in one position, points to a worn cartridge rather than a washer issue.

Tools & materials

Hex key/Allen wrench, adjustable pliers, replacement cartridge or repair kit matching your exact faucet model, plumber's grease.

Step-by-step

1. 1 Shut off water supply valves and drain the line.
2. 2 Remove the handle (often a hex set screw underneath a decorative cap).
3. 3 Use pliers to remove the retaining cap/clip holding the cartridge in place.
4. 4 Pull the old cartridge straight out and replace with an identical new one — orientation matters, so note how the old one was seated.
5. 5 While disassembled, also replace the seats and springs beneath a ball-style mechanism if accessible.
6. 6 Reassemble, lubricate O-rings, and turn water back on gradually.

Root cause

The aerator (the small mesh screen at the tip of the spout) collects mineral sediment and debris over time. This can cause dripping, sputtering, or an uneven stream that's sometimes mistaken for an internal leak.

30-second check

Unscrew the aerator by hand or with pliers wrapped in a cloth. If it's caked with white/green mineral deposits, this is likely contributing to what you're seeing.

Tools & materials

Pliers, white vinegar, an old toothbrush.

Step-by-step

1. 1 Unscrew the aerator counterclockwise from the tip of the spout.
2. 2 Disassemble it and soak the parts in white vinegar for 15–30 minutes to dissolve mineral buildup.
3. 3 Scrub gently with an old toothbrush and rinse.
4. 4 Reassemble and screw back onto the spout, hand-tight.
5. 5 Run the water and check that flow is even and dripping has stopped.

Root cause

If you've replaced the washer or cartridge and the faucet still leaks, the cause may not be inside the faucet at all. Water pressure that's consistently too high stresses every seal in the home's plumbing, causing repeat leaks no matter how many parts you swap. A cracked or corroded supply line behind the wall produces the same symptom but is a hidden plumbing repair, not a faucet repair.

30-second check

Multiple fixtures leak or repeat repairs on the same faucet don't hold — both point away from this specific fixture and toward pressure or supply-line issues.

What a professional actually does

Tests static water pressure at an outdoor spigot or washing machine valve; installs or adjusts a pressure-reducing valve if pressure is above the recommended 40–60 psi range; locates and replaces damaged supply lines, opening walls only as needed and repairing them afterward.