What Causes Kitchen Water Damage Under the Sink?

The most frequent culprit is the flexible supply lines that carry water to the faucet. These braided hoses can develop pinhole leaks or crack at the fittings, especially after years of use. A slow drip often goes unnoticed because it pools under the cabinet and seeps into the wood.

Another common source is the drain assembly. The P-trap and its slip nuts can loosen over time, or the gaskets inside can dry out and fail. Grease and food debris can also cause clogs that back up water, leading to overflow and seepage around the connections.

• Check supply lines for bulges or wet spots
• Inspect the P-trap and drain pipes for drips
• Feel the shutoff valve and connections for moisture
• Look for water stains or warping on the cabinet floor
• Listen for hissing sounds that may indicate a leak

High water pressure puts extra strain on supply lines and connections. Most homes have pressure between 40 and 60 psi, but if yours is higher, it can cause fittings to fail prematurely. A pressure gauge from a hardware store can help you check the level, and a pressure regulator can be installed if needed.

Hot water also accelerates wear on rubber washers and hoses. The constant expansion and contraction from temperature changes can weaken seals over time. If you have a tankless water heater or a recirculating pump, the water may be hotter than normal, increasing the risk of leaks.

Water damage under the sink is not always obvious. Look for soft spots in the cabinet floor, a musty odor, or small insects like fungus gnats that are attracted to damp wood. Discoloration or peeling on the cabinet's exterior can also signal that moisture is traveling upward.

If you suspect a leak, act quickly to dry the area and fix the source. For extensive damage, a water damage inspection can reveal the extent of the problem. Local water damage pros can assess structural issues and recommend repair steps. If you live in Fresno, keep your shutoff valve location written down for emergencies.