The average leaky faucet drips 3,000 gallons a year — about 8 full bathtubs. The repair is one of the most satisfying 20-minute jobs in homeownership. Here's exactly how, broken down by faucet type.

First: identify your faucet type

There are two common designs:

• Single-handle (cartridge): One lever or knob that moves up/down for volume and side-to-side for temperature. Inside is a cartridge — a cylindrical plastic-and-rubber assembly that does all the work.
• Two-handle (compression): Separate hot and cold knobs. Inside each is a stem with a rubber washer at the bottom that presses against a brass seat.

Both are easy to repair. The compression style usually leaks at the spout (worn washer); the cartridge style usually leaks at the base of the handle (worn O-ring) or at the spout (worn cartridge seals).

Universal first step: shut off the water

Look under the sink for two small valves on the supply lines — turn both fully clockwise. If there are no shut-off valves (common in older homes), shut off the main water valve to the house. Open the faucet to relieve pressure.

Plug the drain

Drop a rag in the sink to cover the drain. Cartridge clips and tiny screws love to fall in.

Repairing a single-handle (cartridge) faucet

1. Pop off the decorative cap on the handle (usually a small red/blue disc) using a flathead screwdriver — this exposes a Phillips or Allen screw.
2. Remove the handle by unscrewing that screw and lifting the handle straight up. If it''s stuck, wiggle gently — never pry against the finish.
3. Remove the retaining clip or nut holding the cartridge in place. A pair of needle-nose pliers usually does it.
4. Pull the cartridge straight up. Sometimes you need a cartridge puller (~$10) for stubborn ones. Note the orientation — there''s usually a notch or flat side that has to align on reassembly.
5. Take it to the hardware store — bring the old cartridge with you. Brands like Moen, Delta, Kohler, Pfister all use proprietary designs and the wrong cartridge won''t seal.
6. Install the new cartridge in the same orientation, replace the retaining clip, reattach the handle.
7. Turn the water back on slowly and check for leaks at every connection.

Repairing a two-handle (compression) faucet

1. Pop off the decorative cap on the leaky handle and remove the screw underneath.
2. Pull the handle off. Old chrome handles often need a faucet handle puller.
3. Unscrew the packing nut (large hex nut) with an adjustable wrench.
4. Remove the stem — it usually unscrews counter-clockwise.
5. Look at the bottom of the stem: there''s a rubber washer held by a single brass screw. If it''s flat, cracked, or grooved, that''s your leak. Replace it.
6. Inspect the brass seat down inside the faucet body using a flashlight. If it''s pitted, you''ll need a seat wrench (~$5) to remove it and a matching new seat.
7. Inspect the O-rings on the stem itself — replace any that look hardened or cracked.
8. Reassemble in reverse order, turn water on slowly, check for leaks.

If it still leaks

Re-check that you installed the cartridge with the correct orientation (very common mistake). Also check that you didn''t over-tighten the packing nut on a compression faucet — too tight crushes the rubber washer.

If you''ve replaced everything and the faucet still drips, the faucet body itself may be corroded. At that point, replacing the whole faucet ($40–$200) is more cost-effective than chasing parts.