Fix a Leaky Faucet

A leaky faucet is one of those problems that nags at you—that steady drip in the sink or shower, wasting water and money. The good news is that fixing it rarely requires calling a plumber. The leak almost always comes from one of two places: the washers inside the valve body that have worn thin, or the cartridge itself that controls water flow. Both are cheap to replace and the repair is straightforward enough that anyone with basic tools can do it. What separates a competent repair from a half-done one is taking time to identify which type of faucet you have before you start taking it apart. Once you know that, the rest is methodical disassembly, replacement of the worn part, and reassembly.

1. Kill the Pressure First. Locate the shut-off valves under the sink—there should be two, one for hot water and one for cold. Turn both clockwise until they stop. If there are no valves under the sink, locate the main water shut-off for the house (usually in the basement, garage, or outside near the meter) and turn it off. After shutting off the water, turn on the faucet to release any remaining pressure in the lines.
2. Know Your Faucet Type. Look at your faucet closely. If it has a single lever that moves up-and-down or side-to-side, it's a cartridge faucet. If it has two separate handles (one for hot, one for cold), it's a compression faucet with washers inside. If it has a ball-shaped pivot point under the spout, it's a ball faucet. These three types repair differently, so getting this right matters. Write down your faucet type—you'll use it to buy the correct replacement part.
3. Pop the Cap and Unscrew. For single-lever faucets, look for a small decorative cap or button on the handle itself (usually says 'hot' or 'cold'). Pry it gently with a flat screwdriver to expose the set screw underneath, then unscrew it. For two-handle faucets, you may need to pop off a similar cap on each handle. Once the set screw is out, the handle slides or pulls straight off. Don't force it—if it's stuck, apply a penetrating oil and wait ten minutes.
4. Loosen the Packing Nut. Under the handle you just removed, you'll see a large hexagonal nut (the packing nut) or a decorative trim ring. Use an adjustable wrench to grip it firmly and turn counterclockwise. This nut holds the valve body in place. Turn it until it comes free by hand—don't over-tighten when you reinstall it later, or the faucet will be hard to operate.
5. Pull the Cartridge or Stem. For cartridge faucets, you'll see a cylindrical brass or plastic piece sticking up through the hole. Grip it with a cartridge puller tool (rent one at the hardware store for $5 if you don't own one) or carefully with pliers wrapped in cloth, and pull straight up with steady pressure. For compression faucets with two handles, unscrew the valve stem counterclockwise with a wrench until it comes out completely. Some stems stick—if yours does, apply penetrating oil and wait.
6. Look for the Culprit. Look at what you just pulled out. If it's a cartridge, check the seals at the bottom—they should look firm and intact, not crusty or flat. If they're degraded, that's your leak. If it's a compression stem, unscrew the brass cap at the bottom and look at the rubber washer underneath. If it's thin, cracked, or flattened, that's the culprit. The seat (the metal ring it sits on) should also be smooth. If it's pitted or corroded, you'll need to replace both the washer and the seat.
7. Match the Part Exactly. Take the old cartridge or stem to the hardware store and match it exactly. For cartridges, brands like Moen, Delta, and Kohler are common—get the exact model for your faucet. For compression faucets, buy a universal washer kit and a valve seat if needed. Don't guess on cartridges; a wrong one won't fit and you can't return it. Bring your faucet photo if you're unsure.
8. Replace the Valve Seat. If you're replacing a compression washer and found a pitted valve seat, remove it now. Insert a valve seat wrench (a specialized socket) into the faucet body and turn counterclockwise until the seat comes free. Screw the new seat in by hand first, then snug it with the wrench. Don't over-tighten. If the seat looks clean and smooth, skip this step.
9. Seat the New Part. For compression faucets, slide the new rubber washer onto the stem and screw the brass cap back on finger-tight, then snug it with a wrench. For cartridge faucets, insert the new cartridge straight down into the body, aligning any tabs or notches so it sits flush. Push down firmly until it stops. The top should sit level with the faucet body. If it's crooked, pull it out and reorient it.
10. Put It Back Together. Screw the packing nut back on by hand, then snug it with the wrench—firm enough to hold the valve body steady, but not so tight the handle becomes hard to turn. Slide the handle back onto the stem or cartridge, insert the set screw, and tighten it. Pop the decorative cap back on. Do this in reverse order of how you took it apart.
11. Test for Leaks. Turn both shut-off valves counterclockwise slowly. Listen and watch for leaks under the sink as the water pressure builds. Turn on the faucet and let it run for 30 seconds to clear any air bubbles. Test both hot and cold water. Move the handle through its full range. Check under the sink again for any drips. If there's a small drip at the base of the spout where it meets the faucet body, that's normal for the first few minutes—it'll stop. If water runs continuously from the base or the spout doesn't shut off cleanly, you may have the wrong cartridge or it's not fully seated.
12. Tidy and Recycle. Wipe down the sink and faucet with a dry cloth. Put the old cartridge or stem in the recycling bin if your area accepts brass and plastic, or save it in a drawer—you may need to reference the model number someday. Wipe up any water you spilled during the repair. If you rented a cartridge puller, return it to the hardware store.