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Under-Sink Water Damage: How to Find and Fix It Early

Last updated October 25, 2026

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The short answer

Signs of Under-Sink Water Damage

Start by looking under the sink for visible clues. Check the cabinet floor for dark stains, warping, or soft spots. Feel the wood with your fingers; if it gives easily, water has soaked in. Look at the pipes and connections for drips, mineral buildup, or rust streaks.

Also check the walls inside the cabinet and the area around the sink base. Peeling paint, bubbling wallpaper, or a musty smell are strong indicators. If you notice any of these, act quickly. The longer water sits, the more damage it causes to the cabinet and subfloor.

Find the Source of the Leak

The leak often comes from a loose connection, a worn washer, or a cracked pipe. Turn on the water and watch the pipes while the sink drains. Look for drips at the joints, around the faucet base, or where the supply lines connect. Also check the drain trap and the seal where the sink meets the counter.

If the leak is not obvious, dry the area completely with a towel, then place a piece of paper towel under the pipes. Check it later for moisture. In some cases, the leak may come from the wall behind the cabinet, especially if the water stains appear high up. If you cannot find the source, a plumber can help pinpoint it.

  • Check supply lines and shutoff valves for dampness
  • Inspect the drain pipe and P-trap for cracks
  • Feel the floor of the cabinet for softness
  • Look for water stains on the back wall of the cabinet
  • Run water and watch for drips in real time

Shut off the Water and Dry Out

Once you find a leak, shut off the water supply to the sink. Look for the shutoff valves under the sink, usually two small handles. Turn them clockwise to close. If there are no valves, turn off the main water valve for your home. Knowing where these valves are before an emergency helps you act fast.

After shutting off the water, remove everything from under the sink. Use towels to soak up standing water, and set up a fan to circulate air. If the cabinet floor is wet, place a dry towel or rag underneath to wick moisture away. Leave the cabinet doors open to let the area dry thoroughly.

Remove Damaged Materials Safely

If the cabinet floor is soft or swollen, it needs to be removed. Use a pry bar or screwdriver to carefully lift the damaged particleboard. Wear gloves and a dust mask, as old materials may contain mold or dust. Also remove any wet insulation or cardboard that may be under the sink.

Check the drywall behind the cabinet for water stains or sagging. If the drywall is soft, cut out the damaged section with a utility knife. Leave the area open to dry before replacing anything. For large areas of damage, the pros can handle the removal and repair, especially if the subfloor is involved.

When to Call the Pros

Minor leaks you can fix yourself, but extensive water damage needs professional help. If the water has soaked into the subfloor, spread to the walls, or caused mold, call local water damage pros. They have the tools to dry out hidden areas and the experience to restore the space properly.

If you live in Burnsville, keep your shutoff valve location written down. The pros can also inspect the surrounding area for damage you might miss. For a full assessment, consider a water damage inspection. If the cabinet or drywall needs replacement, drywall water damage repair services can help. Act quickly to prevent further issues.

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Frequently asked questions

How can I tell if my under-sink leak is serious?

Serious leaks cause soft, spongy cabinet floors, visible mold, or water stains that spread to walls or the ceiling below. If the leak is small and you find it early, you can often fix it yourself. If the damage is extensive, call the pros.

What should I do if I find mold under my sink?

Mold under the sink means moisture has been present for a while. Dry the area completely and remove any moldy materials. Wear gloves and a mask. If the mold covers a large area or you have health concerns, see a doctor if you feel unwell and consider calling a mold professional.

Can I fix a leaking pipe under the sink myself?

You can fix a loose connection or replace a worn washer yourself. Tighten fittings with a wrench, but be careful not to overtighten. If the pipe is cracked or the leak is from the wall, you may need a plumber. If water has damaged the cabinet, the pros can repair it.

Call Now (952) 522-6744