How to Fix a Leaky Faucet: A Master Plumber's Step-by-Step Guide

Diagnose the Leak Before You Touch a Wrench

Before you start pulling things apart, figure out where the water is actually coming from. A drip from the spout is a different problem than a drip from the base of the handle, and the fix is different too.

A drip from the spout when the handle is off means a worn cartridge or washer. A leak around the base of the handle when the water is running means a failed O-ring. Water pooling under the sink usually means a bad supply line, a loose compression nut on the angle stop, or a cracked faucet body. That last one is not a DIY fix.

Next, identify your faucet type. A single-handle kitchen faucet is almost always a cartridge or ball-style. A two-handle bathroom faucet built before the mid-1980s is probably a compression faucet with rubber washers. Newer two-handle faucets typically use ceramic disc cartridges. If you can't tell by looking, take a photo of the faucet and the brand stamp and match it at the hardware store.

Tools and Parts You'll Need

You don't need a plumber's truck. You need five things:

• Adjustable wrench and a set of hex (Allen) keys for set screws.
• Channellock pliers with the jaws wrapped in electrical tape or a rag so you don't scratch the finish.
• Phillips and flathead screwdrivers.
• Plumber's grease (silicone-based, not petroleum) for O-rings and cartridges.
• The exact replacement part: cartridge, washer kit, or O-ring set. Match the brand and model. A Moen 1225 cartridge is not interchangeable with a Moen 1222. Bring the old part to the store if you can.

Budget $8 to $25 for parts on a standard repair. A genuine Delta, Moen, or Kohler cartridge runs $15 to $30.

Fixing a Cartridge Faucet

Cartridge faucets are the most common single-handle design in homes built after 1990.

1. Shut off the water at both angle stops under the sink. Open the faucet to relieve pressure and confirm the water is off.
2. Pop off the decorative cap on the handle with a flathead. Remove the handle screw underneath (often a Phillips or hex).
3. Lift the handle straight up and off. Remove the retaining clip or retaining nut holding the cartridge. A Moen uses a brass retaining clip you pull with needle-nose pliers. A Delta uses a bonnet nut.
4. Pull the cartridge straight out. If it's stuck, a cartridge puller (about $15) is worth buying before you destroy the faucet body trying to pry it out.
5. Install the new cartridge in the same orientation as the old one. Hot and cold reversed is the number one rookie mistake. Look for the tab or notch that indexes it.
6. Reassemble, turn the water back on slowly, and run the faucet for 30 seconds before checking for leaks.

Fixing a Compression (Washer) Faucet

If your faucet has two separate handles and the house predates the Reagan administration, you probably have a compression faucet. These leak because the rubber washer at the bottom of the valve stem hardens and cracks.

1. Shut off the water and open the handles.
2. Remove the handle screw (usually under a decorative H/C cap) and pull the handle off.
3. Unscrew the packing nut with an adjustable wrench. Then unscrew the stem itself by turning it the same direction you'd turn the handle to open the water.
4. Flip the stem over. There's a brass screw holding a small rubber washer on the bottom. Replace that washer with an exact-size match. While you're in there, replace the O-ring on the stem body.
5. Reassemble and test. If the faucet still drips with a new washer, the valve seat inside the faucet body is pitted. You can resurface it with a seat wrench (cheap) or replace the seat itself if it's a removable style.

Fixing a Ball or Ceramic Disc Faucet

Ball faucets (common on older Delta kitchen faucets) have more small parts than a jigsaw puzzle. Buy a full repair kit — don't try to replace just one thing.

1. Shut off the water. Remove the handle set screw with a hex key and lift the handle off.
2. Unscrew the cap with taped pliers. Lift out the cam, ball, and rubber seats with their springs.
3. Replace the seats and springs (they come in the kit). Replace the cam washer. If the ball is scored or pitted, replace the ball too.
4. Reassemble with plumber's grease on the O-rings and cam. Hand-tighten the cap, then snug it with pliers — don't gorilla it.

Ceramic disc faucets rarely fail, but when they do, the whole cartridge cassette gets replaced as a unit. Same process: shut off, disassemble, swap, reassemble.

When to Stop and Call a Plumber

Knowing when to quit is the mark of a good DIYer. Stop and call a plumber if:

• The angle stop won't shut the water off. Corroded or seized stops are common in Carlsbad and North County San Diego because of our hard water. Forcing a stuck stop can snap the supply line off at the wall. That's a flooded kitchen, not a faucet repair.
• The faucet body is cracked or leaking from the base where it meets the sink. That means a full faucet replacement and new supply lines, which is worth doing right the first time.
• You strip a screw, break a cartridge off inside the valve body, or can't get the old cartridge out. Every plumber I know has fixed a DIY job that cost the homeowner three times what the original repair would have. If you're an hour in and things are going backwards, call.
• You smell sewage or see water damage in the cabinet below. That's no longer a faucet problem.

A $150 service call to finish what you started is still cheaper than $2,000 in water damage. Know your limits and you'll save money over the long run.