Why Do Kitchen Pipes Leak Under the Sink?

The small rubber or plastic seals inside your faucet handles and shutoff valves degrade with constant use. These washers and O-rings become brittle and lose their shape, allowing water to seep past them. This often causes a slow, steady drip from the supply lines under your sink. Replacing these components requires turning off the water and disassembling the connections.

Older metal pipes, especially chrome-plated brass, can corrode from the inside out. This corrosion creates pinhole leaks that are hard to spot. Plastic PVC or ABS pipes can become brittle and crack from age or impact. A small crack might only leak when water runs down the drain, making the source difficult to locate without a careful inspection.

Corrosion is often worse on hot water lines due to the constant heat. If you see green or white crusty deposits on pipe fittings, that is a sign of corrosion. A cracked pipe usually requires a section to be cut out and replaced. For persistent or hidden leaks, local water damage pros use specialized tools for detection.

A clog in the drain pipe creates back pressure, forcing water to find another escape route. This often means it leaks out at the weakest joint under the sink. Grease, food particles, and soap scum are common culprits for kitchen sink clogs. The leak may only occur when the sink is actively draining a full basin of water, confusing the diagnosis.

Clearing the clog with a plunger or drain snake may stop the leak if the joints are still sound. However, the pressure from the clog may have already compromised a gasket or loosened a nut. After clearing the blockage, run water and check all connections for drips. Persistent drainage issues might indicate a deeper clog in the main line.

• Food grease solidifying in the pipes.
• Coffee grounds and food scraps.
• A blocked garbage disposal.
• Soap residue building up over time.
• Objects accidentally dropped down the drain.
• Tree root intrusion into the main sewer line.