The short answer
Check the Supply Lines
The flexible braided hoses that carry hot and cold water to the faucet are a common leak source. The nuts where they connect to the shutoff valves or the faucet base can loosen over time. A tiny drip at these fittings can run down the pipes and pool under the sink, making it look like the leak is somewhere else.
Inspect the full length of each hose for cracks, bulges, or damp spots. If the hose feels wet or shows mineral buildup, that points to a slow leak. Tighten the connections with a wrench, but avoid over-tightening, which can strip the threads. If the hose itself is damaged, replacement is the reliable fix.
Inspect the Drain Assembly
The drain pipes under your sink consist of several pieces: the tailpiece from the sink basket, the P-trap, and the horizontal pipe leading to the wall. Each slip joint has a washer and a nut. If any nut is loose or the washer is worn, water can escape when you run the faucet.
Run water and watch the joints closely. Look for drips at the P-trap and where the tailpiece meets the sink basket. The rubber gasket at the top of the tailpiece can dry out and crack, causing a leak that only appears when the sink is full. Replacing these gaskets is a straightforward repair.
Look at the Sink Rim and Seal
If your sink is a drop-in model, the seal between the sink rim and the countertop can fail. Water that splashes onto the counter can seep under the rim and run down the sides of the sink, eventually showing up as moisture in the cabinet below. This type of leak is often intermittent and hard to spot.
Check the caulk or silicone bead around the sink edge. If it is cracked, peeling, or missing in spots, that is an invitation for water to get behind. Reapply a fresh bead of kitchen-grade silicone caulk to restore the barrier. Also check the underside of the rim for any visible gaps.
Trace Water from Above
Sometimes the leak under your sink is not from the sink itself. Water from a leaking pipe inside the wall or from an appliance above, like a refrigerator with an ice maker line, can run down and collect under the sink. The moisture you see may be the end point of a longer path.
Feel the pipes where they enter the wall. If they are wet higher up, the source could be in the wall cavity. Also check the underside of the cabinet floor for water stains or soft spots. If you suspect a hidden leak, a water damage inspection can help locate it without tearing things apart.
When to Call a Pro
You can handle a loose nut or a cracked hose yourself. But if the leak persists after you have checked the connections, or if you see water staining on the cabinet floor, the problem may be deeper. A plumber can replace worn parts inside the wall or under the sink.
If water has already soaked the cabinet, the particleboard may swell and grow mold. In that case, the pros can remove damaged materials, dry the area, and treat any mold. Keep your shutoff valve location written down so you can stop the water while you wait for help.
- Turn off the water at the shutoff valve before any repair.
- Place a bucket under the leak to catch drips while you investigate.
- Dry the cabinet thoroughly to prevent mold growth.
- Replace any cracked or brittle hoses rather than patching them.
- Use plumber's tape on threaded connections for a tighter seal.
- If you are unsure, call a plumber first, then a water damage pro if needed.
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Call Now (469) 698-4610Frequently asked questions
How do I find the shutoff valve for my kitchen sink?
Look under the sink for two small valves, one for hot and one for cold. They are usually on the wall or floor where the pipes come in. If you cannot find them, check the main water shutoff for your home. Knowing the location now will save you time during a leak.
Can I fix a cracked P-trap myself?
Yes, if the crack is visible and the pipe is accessible. You can buy a replacement P-trap at a hardware store and install it with slip nuts and washers. Turn off the water and place a bucket underneath. If the crack is hidden or the pipe is corroded, a plumber can handle it.
What should I do if the leak has already soaked the cabinet?
Stop using the sink and turn off the water. Remove any items from the cabinet and dry the area with towels and a fan. If the wood is soft or swollen, it may need replacement. The pros can extract water and dry the structure to prevent mold. See a doctor if you feel unwell from any mold exposure.