Symptoms
- Puddle or drip inside the cabinet
- Cabinet floor or shelf paper is damp or warped
- Musty smell under the sink
- Leak worse when the faucet is running
Likely causes
- CommonLoose supply line connectionCompression or braided lines can loosen from vibration or age.
- CommonWorn supply line washer or gasketRubber washers inside fittings dry out over years.
- PossibleLoose faucet mounting nutLets water seep down the faucet shank onto the cabinet floor.
- PossibleCracked supply lineBraided lines can corrode or split, especially older ones.
What to do
- Turn off both shutoff valves under the sink before touching anything.
- Dry everything with a towel, then run the faucet briefly and watch closely to spot exactly where water appears.
- If it's at a supply line connection, tighten the nut a quarter turn with an adjustable wrench.
- If tightening doesn't stop it, turn off water, disconnect the line, and check the washer or gasket inside for wear.
- Replace a cracked or bulging supply line entirely rather than trying to patch it.
- If water is coming from around the faucet base itself, tighten the mounting nut(s) underneath from below.
- Turn the water back on slowly and recheck for drips at each connection point.
- Place a small tray or towel under the area for a day to confirm the leak is fully stopped.
Tools and parts
- Adjustable wrench
- Basin wrench
- Flashlight
Braided supply lineSearch: “braided faucet supply line 3/8 inch”
When to call a pro
Call a plumber if the leak is at the faucet body itself, you can't reach the fittings, or the shutoff valves themselves are leaking.
Safety
Generally low risk
Generally low risk for a careful person. Stop if anything looks different from what this guide describes.