How to Fix a Kitchen Sink Leak

Water underneath your kitchen cabinet is a slow-motion disaster that silently wreaks havoc on your subfloor and cabinetry. Whether it is a slow drip or a sudden spray, the moisture will inevitably lead to warping wood, mold, and a persistent musty smell that is nearly impossible to scrub away once it sets into the particle board. Fixing this is a classic weekend win that requires more patience than specialized plumbing skill. Most leaks stem from vibrations over time loosening connections or old washers that have finally lost their flexibility. By working methodically—clearing the space, pinpointing the exact drip point, and resealing the joints—you can stop the damage before it compromises your kitchen's structural integrity.

1. Clear the workspace. Remove all cleaning supplies and items from under the sink. Wipe every pipe and joint bone-dry with a rag so you can spot exactly where the fresh water appears.
2. Find the leak source. Place a dry paper towel under the pipes and run the faucet. Watch closely for the first dark spot on the towel to identify which joint or connection is compromised.
3. Hand-tighten first. Try tightening the plastic or metal slip-joint nuts by hand. If they are stubborn, use channel-lock pliers, but be careful not to overtighten and crack plastic fittings.
4. Swap the washers. If tightening fails, unscrew the leaking nut completely and slide the old washer off the pipe. Inspect it for cracks, flatten, or buildup; replace it with a new washer of the exact same size.
5. Prep the pipes clean. Wipe away any old, hardened plumber's putty or debris from the pipe threads before reconnecting. Ensure the pipe ends are square and free of hairline cracks.
6. Verify the fix works. Run the faucet for several minutes while watching the joints. If the paper towel stays dry, the leak is resolved.