How to Fix a Leaking Kitchen Sink and Faucet

Kitchen sink leaks are the home plumber's bread and butter, and for good reason: they're predictable, fixable, and they get worse the longer you ignore them. A dripping faucet wastes water, stains your sink, and creates that maddening sound at 2 a.m. Worse, water pooling under the sink rots cabinets and attracts pests. The leak might be coming from the faucet spout, the base, or the drain connections—each one tells you something different about what's actually broken. The difference between a $5 fix and a $300 faucet replacement often comes down to where the water is actually coming from and how much patience you have with disassembly. Most leaks happen because washers wear out, valve seats corrode, or compression nuts simply loosen over time. If you've got a single-handle or cartridge faucet, the repair gets slightly more involved but still manageable at home. The key is identifying which part is failing before you order anything or start tearing things apart. Water pooling under the sink but the faucet appears dry? You're dealing with connection leaks. Water dripping from the spout even when the handle is off? That's a valve seat or washer problem. Base of the faucet sweating? That usually means the faucet itself is done, and replacement is your real option.

1. Kill the Water First. Look under the sink at the pipes. You should see two small oval valves (hot and cold) connected to the supply lines. Turn both clockwise until they stop. If you don't have shutoff valves, shut off water at the main and plan to install angle stops while you're under there. Open the faucet to release any remaining pressure in the lines.
2. Pinpoint the Source. Dry the area completely with a towel. Watch for 30 seconds to see where water appears first. Is it dripping from the spout when the handle is turned off? Coming from the base of the faucet where it meets the sink? Pooling under the cabinet from the drain connections? Is it a steady drip or a slow weep? The location tells you exactly what part to fix.
3. Expose the Packing Nut. If water is dripping from the spout, the washer or valve seat is worn. Look for a small cap or set screw on top of the handle (often hidden under a decorative button or plug). Pop it off with a flat screwdriver if needed. Unscrew the handle screw and lift the handle off. You should now see a packing nut—a hexagonal nut directly under where the handle was. Place a bucket underneath to catch drips.
4. Extract the Stem. Using an adjustable wrench, turn the packing nut counterclockwise. You may need to hold the base of the faucet steady with your other hand. Once the nut is loose, pull the stem straight up and out. This is the barrel that contains the washer and valve seat. You'll see a small flat washer on the bottom end of the stem, often made of rubber or plastic.
5. Swap Washer, Clean Seat. Remove the small screw holding the washer at the bottom of the stem. Pop out the old washer and replace it with an exact match (bring the old one to the hardware store if you're unsure of the size). While you're at it, look inside the faucet body for the valve seat—it's the small brass or rubber ring at the bottom. If it's corroded or pitted, rub it with a brass brush or fine abrasive pad. If it's badly damaged, you can use a valve seat dresser tool, but replacement is more reliable.
6. Reinstall Stem. Slide the stem back into the faucet body, aligning the slot on top of the stem with the pin inside the faucet. Screw the packing nut back down by hand, then tighten with your wrench. Don't over-tighten—just snug enough that you can't wiggle it. Replace the handle and its set screw or cap.
7. Verify the Fix. Open the shutoff valves under the sink slowly—turn them counterclockwise about one and a half rotations. Turn on the faucet handle and let water run for 10 seconds. Turn it off and watch the spout. If water still drips, you either need a new valve seat or the faucet is beyond repair. If the leak is fixed, dry the entire area and watch for 30 minutes to confirm it's holding.
8. Tighten Compression Nuts. If water is pooling under the cabinet from the supply lines or drain connections, the issue is a loose nut. Using two wrenches (one to hold, one to turn), tighten the compression nuts where the supply lines connect to the shutoff valves. Then check the nuts connecting the drain tailpiece to the P-trap. Tighten these as well. Turn water back on and let it run into the sink for 30 seconds while you watch underneath.
9. Install New Supply Lines. If tightening didn't work, turn off the water again. Using two wrenches, disconnect the compression nut at the shutoff valve and the nut at the faucet. Pull the old line out and take it to the hardware store to match the length and thread type. Install the new line, hand-tightening first, then using wrenches to seat it firmly. Repeat for the other line if needed. Turn water back on and test.
10. Reseal P-Trap. If the leak is coming from where the drain tailpiece meets the P-trap, turn off the water. Place a bucket under the P-trap and unscrew the slip nut (the large nut at the top of the trap). Slide it down the pipe. Check the rubber washer inside—if it's cracked, swollen, or missing, replace it with a new one. Reinstall the nut and tighten by hand, then a quarter turn with a wrench. For drain leaks that won't stop, you may need a new P-trap assembly.
11. Install New Faucet. Leaks at the base of the faucet where it meets the sink usually mean the seal is shot and can't be fixed. Turn off water, disconnect the supply lines and drain tailpiece, then unscrew the mounting nuts under the sink. Lift out the old faucet and clean the surface where it sat. Install the new faucet following the manufacturer's instructions—it will come with new supply lines and a drain collar. Tighten everything snugly and test before you close the cabinet.