Clean or Resurface Valve Seat

If replacing the washer does not stop the drip, the valve seat is likely the problem. The valve seat is the metal surface inside the faucet body where the washer presses to create a seal. Over time, mineral deposits or corrosion pit this surface, preventing a tight seal.

Inspection

Turn off the water supply and disassemble the faucet stem. Look inside the faucet body and feel the valve seat with your finger. A rough, uneven, or pitted surface indicates damage.

Cleaning

Wipe the valve seat with a cloth soaked in white vinegar to dissolve mineral buildup. For light corrosion, scrub gently with a fine abrasive pad.

Resurfacing

For deeper damage, insert a valve seat dresser tool into the faucet body and rotate it to grind the seat smooth. Apply even pressure and check the surface periodically. If the seat is too damaged to resurface, some faucets allow the seat to be unscrewed and replaced entirely.

Reassembly

Install a new washer, reassemble the stem and handle, and restore the water supply. Test for drips.