Why Is My Sink Leaking Underneath?

If water is leaking under your sink, the cause is usually a loose pipe connection, worn washer, or cracked fitting rather than a burst pipe. Most under-sink leaks occur at joints or seals. In many cases, the problem is confined to the cabinet area rather than the wider plumbing system.

The Most Common Reasons

1. Loose Drain Fittings

Connections may loosen over time.

2. Worn Washer or Seal

Rubber washers degrade and allow drips.

3. Cracked Trap or Pipe

Plastic pipes can develop hairline cracks.

4. Supply Line Leak

Flexible supply hoses may leak at fittings.

If taps also drip:

Tap Problems Explained

Is This Serious?

Minor if:

  • Leak is slow
  • Only one joint is wet

More serious if:

  • Cabinet wood swells
  • Leak continues when taps are off

What You Can Do

  • Dry area and identify source
  • Tighten fittings carefully
  • Monitor after use

For related issues:

Sink & Drain Problems Explained
Plumbing Problems Explained