Leak Under the Kitchen Sink? How to Stop Cabinet Water Damage
Most leaks under a kitchen sink come from a loose drain fitting, a worn supply line or valve, the garbage disposal or the dishwasher hose. Close the valves under the sink, empty the cabinet, dry everything and leave the doors open. Check the floor and wall behind the cabinet, because water often spreads where you cannot see.
The cabinet under the kitchen sink holds a lot of plumbing in a small space: two supply lines, a drain, often a garbage disposal and a dishwasher hose. A small drip can go unnoticed for weeks behind cleaning supplies. By the time you see it, the cabinet floor may be swollen and the water may have reached the flooring. This guide covers the causes, what to do first and what can be saved.
Reading this with water on the floor? Get help first.
Need Help Now? Tap Here(833) 937-0179What causes leaks under a kitchen sink?
| Source | What to look for |
|---|---|
| Drain trap and slip nuts | Drips under the curved pipe when the sink drains |
| Supply lines and shut-off valves | Wet lines or valves, drips even when the sink is off |
| Garbage disposal | Water at the bottom or side of the disposal |
| Dishwasher drain hose | Water during or after the dishwasher runs |
| Faucet base or sprayer hose | Water around the faucet or dripping from above |
| Water filter or reverse osmosis system | Wet tubing, filter housings or the tank |
Arizona's hard water leaves mineral buildup that can wear out valves and fittings. Valves that have not been turned in years may also leak when you finally close them.
What should I do first?
- Close the two valves under the sink. If they will not close or still leak, close the main water shut-off.
- Do not run the dishwasher or disposal until the leak is fixed.
- Empty the cabinet and wipe up standing water.
- Take photos of the leak, the cabinet and any stained flooring.
- Leave the cabinet doors open and run a fan to move air.
Not sure where your main valve is? See how to find your main water shut-off.
Has the water spread past the cabinet?
Often, yes. Water runs to the back of the cabinet and into the wall, or under the cabinet base and into the flooring. Check for these signs:
- Swollen or stained toe kick at the bottom front of the cabinet.
- Loose, cupped or stained flooring in front of the sink.
- Peeling paint or soft drywall on the wall behind or next to the cabinet.
- A musty smell when you open the doors.
A restoration crew can check behind and under cabinets with a moisture meter. They may remove the toe kick to dry the space under the cabinet without taking the whole cabinet out.
Can a water damaged sink cabinet be saved?
It depends on what the cabinet is made of and how long it was wet. Many cabinet floors are made of particleboard, which swells and crumbles when wet and does not go back to normal. Plywood holds up better and can often be dried if caught early. A swollen cabinet floor can sometimes be replaced with a new panel without replacing the whole cabinet. If mold is growing, the affected parts should be removed. Learn more in what can be saved after water damage.
How can I prevent sink leaks?
- Look under the sink once a month with a flashlight.
- Replace old supply lines with braided steel lines.
- Turn the shut-off valves once or twice a year so they do not seize.
- Put a leak sensor or a tray under the sink.
- Do not store heavy items that can bump the drain pipes.
The EPA's WaterSense program has more tips on finding and fixing household leaks.
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Get Expert Help 24/7(833) 937-0179Frequently asked questions
Why is the cabinet under my sink wet but I see no leak?
The leak may only happen while the sink drains or the dishwasher runs. Run each one while you watch with a flashlight and a dry paper towel.
Can I dry a swollen sink cabinet floor?
Particleboard that has swollen usually stays swollen. The panel can often be replaced. Plywood may dry if caught quickly.
Is a leaking garbage disposal worth fixing?
A leak at the drain or dishwasher connection can often be tightened. A leak from the bottom of the unit usually means it needs to be replaced.
How long does it take to dry under a sink cabinet?
Small leaks may dry in a day or two with open doors and a fan. Water under the cabinet or in the wall can take several days with drying equipment.
Will insurance cover a kitchen sink leak?
A sudden failure, like a burst supply line, is often covered. A slow drip over weeks may be treated as wear and tear. Check your policy.
About the author
Noah Miller founded AZ Water Damage Help in Queen Creek to give Arizona homeowners fast, honest water damage help. He writes and updates these guides using public guidance from the EPA, the IICRC, the National Weather Service and Arizona state agencies. More about Noah.
Sources
- EPA WaterSense: Fix a Leak Week
- EPA: Mold
- IICRC (Institute of Inspection, Cleaning and Restoration Certification)