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Why Is There Standing Water Under My Kitchen Sink?

Last updated October 31, 2026

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The short answer

Check the Supply Lines

The water supply lines that connect to your faucet are a common source of leaks. The nuts that hold them can loosen over time, or the rubber washers inside can wear out. Even a tiny drip from a supply line can create a puddle under the sink, especially if it runs for hours while you are away.

Look for moisture around the base of the faucet and along the lines. If you see water droplets, tighten the connections with a wrench, but do not overtighten. If the lines are old or cracked, replacing them is a straightforward job. Turn off the shutoff valves under the sink before you start.

Inspect the Drain Trap

The drain trap, the curved pipe under the sink, is another frequent culprit. The slip nuts that hold the trap in place can loosen, or the pipe can crack from age or strain. Food debris and grease can also cause a backup that forces water out of the joints. A slow leak from the trap often goes unnoticed until you see standing water.

Place a dry towel under the trap and run water for a few minutes. Check the towel for any wet spots. If you find a leak, tighten the slip nuts or replace the washers. Clean out any buildup inside the trap. If the trap is corroded, a new one is inexpensive and easy to install.

Look at the Dishwasher Hose

If your dishwasher drains through the sink, the hose connection can leak. The hose clamp may be loose, or the hose itself may have a pinhole. Water can run down the hose and pool under the sink without you noticing. This is especially common if the dishwasher is not used often, as seals can dry out.

Check the hose where it connects to the drain line under the sink. Feel the hose for dampness along its length. Tighten any clamps, and replace the hose if it is cracked or brittle. Make sure the hose has a high loop to prevent backflow, which can also cause water to spill out.

Find the Shutoff Valve

Knowing where your water shutoff valve is can save you from further damage. The valve is usually under the sink, but it may be in the basement or near the water meter. If the leak is severe, turn off the water quickly. If you live in Columbus, keep the location of the shutoff valve written down for emergencies.

Once the water is off, you can safely inspect the area. Dry up the standing water with towels or a wet-dry vacuum. Remove any items stored under the sink. This also gives you a clear view of where the water is coming from. A dry cabinet makes it easier to spot the source.

When to Call the Pros

Some leaks are simple to fix, but others may require more skill. If you cannot find the source, or if the leak is behind the wall, you may need a plumber. Water that has soaked into the cabinet floor or the subfloor can lead to rot and mold. In that case, water damage pros can help with extraction and drying.

If you notice warped wood, a musty smell, or discoloration, the damage may go deeper than the surface. The pros can assess the extent of the water damage and recommend the right steps. They have the tools to dry out hidden areas and prevent mold growth. Acting quickly can reduce the risk of long-term issues.

Turn off the water supply before doing any work.

Use a flashlight to check for slow drips.

Run water for a few minutes while you watch for leaks.

Tighten connections gently to avoid stripping threads.

Replace any cracked or worn hoses and washers.

If you see mold, call a mold professional.

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Water keeps spreading into floors and walls, so it is worth acting early. Calls are answered 24/7.

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Frequently asked questions

How do I know if the leak is from the sink or the wall?

Dry the area completely, then watch where the water appears. If it comes from the back of the cabinet, it may be a pipe in the wall. If it drips from the bottom of the sink, it is likely a fitting or seal. A plumber can help if you are unsure.

Can I fix a leaking sink myself?

Many sink leaks are simple to fix with a wrench and new washers. You can tighten connections or replace the drain trap. If the leak is from a cracked pipe or behind the wall, you may need a plumber. Turn off the water first to avoid making a mess.

What should I do if the water damaged the cabinet?

Dry the cabinet as soon as possible. Use a fan or dehumidifier to speed up drying. If the wood is swollen or soft, it may need replacement. Water damage pros can assess the subfloor and remove damaged materials. They can also check for mold growth.

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