How to Fix a Leaky Pipe Under the Sink (and When to Call an Akron Plumber)

You open the cabinet under the sink, see water, and your stomach drops. We get it. The good news: under-sink leaks almost always come from one of four predictable spots, and two of them you can fix yourself in under an hour with parts that cost less than lunch.

This guide covers finding the leak, the two repairs that are safe to DIY, and the situations where calling a plumber saves you money instead of costing it.

Step 1: Find the source. Don’t guess.

Grab a flashlight and a roll of paper towels. Dry every pipe, fitting, and hose until the whole cabinet is bone dry. Then run two tests:

1. Run the faucet for 30 seconds and watch closely.
2. Fill the sink halfway, pull the stopper, and watch again while it drains.

That second test matters. A lot of under-sink leaks only show up under drain pressure, not supply pressure. Run the faucet alone and a drain leak can hide on you completely.

One more trick: water travels. A drip often runs along the pipe before it falls, so the wet spot on the cabinet floor is not always directly below the leak. Follow the moisture uphill to the highest wet point. That’s your source.

The four usual suspects

• Drip at the small shutoff valve where the supply line meets the wall: supply leak.
• Drip from the underside of the faucet base: faucet seal.
• Drip at the slip nuts on the curved trap: P-trap leak. This is the most common one by a wide margin.
• Drip where the drain pipe enters the wall: drain connection, or possibly a problem inside the wall.

The first two on the supply side leak constantly because they’re under pressure. The drain-side leaks only run when water moves through them. That difference matters for how urgent your situation is.

DIY fix 1: The P-trap

The P-trap is the U-shaped pipe under your sink. Its job is to hold a little water that blocks sewer gas. Its slip nuts loosen over time, and the washers inside them flatten out and stop sealing.

Here’s the fix:

1. Put a bucket under the trap. It’s full of water and whatever went down the drain last.
2. Loosen both slip nuts by hand. Most are plastic and don’t need tools.
3. Drop the trap and dump it in the bucket.
4. Check the washers inside each nut. If they’re flattened, cracked, or missing, replace them. Better yet, replace the whole trap. A complete trap kit runs about $8 at any hardware store in Akron or Wadsworth.
5. Reinstall hand-tight, then go about a quarter turn past snug. Stop there. Plastic slip nuts crack at maybe a quarter turn past snug, and an overtightened trap leaks worse than a loose one.

While the trap is off, look inside it. If it’s packed with grease or hair, that buildup is why your sink drains slow. Clear it before you reinstall, and if the clog sits deeper than the trap, that’s a job for drain cleaning rather than more wrenching.

DIY fix 2: The supply line

Turn off the angle stop. That’s the small valve where the supply line meets the wall. Righty-tighty, all the way closed. Then:

1. Unscrew the braided line at the valve.
2. Check for a missing or pinched rubber washer inside the connection. That’s the cause more often than not.
3. Re-seat the washer and snug the connection with a crescent wrench. Hand-tight plus a quarter turn. No more.

If the braided line is wet along its whole length, not just at the ends, the line itself is failing. Replace it. New supply lines cost about $6 and are rated for roughly 10 years. If yours came with the house and you have no idea how old it is, replace it anyway while you’re in there. It’s the cheapest insurance in plumbing.

When to put the wrench down and call

Some under-sink problems look small and aren’t. Call a plumber when:

• The shutoff valve itself drips, won’t close, or weeps from the stem. A failed angle stop means you can’t isolate the leak, and replacing one usually means shutting water off to the whole house.
• Water is coming from inside the wall or from the drain-to-wall connection. In-wall leaks need to be opened up and inspected, not guessed at.
• You see corrosion, white crust, or green oxidation on copper. That pipe is failing from the inside. Tightening fittings won’t save it.
• The cabinet floor is soft or stained. That leak has been running for weeks. The wood is compromised and mold may already be growing behind it.

One more, learned from years of ceiling-leak calls around Akron: if water is showing up in the ceiling below your kitchen and you can’t tell whether it’s a supply or drain leak, shut off the main water valve to the house. A drain leak only runs when you use the fixture above it. A supply leak runs all day, and you don’t want to find out which one you have by flooding the living room.

If water is actively spraying or a valve won’t close, that’s an emergency, and we answer those calls day and night. Start with our emergency plumbing page or just call 330-825-3686.

What this costs around Akron

If you DIY a trap or supply line, you’re out $6 to $15 in parts and an hour of your Saturday.

If a plumber handles it, flat-rate under-sink repairs typically run $175 to $275 around greater Akron. Bigger leaky-pipe jobs, like corroded copper or anything in-wall, can land anywhere from $175 to $650 depending on access and pipe condition. Our dispatch fee is $79 in the core area and $89 for greater Akron, and it rolls into the job if you approve the work. You’ll see the full price in writing before anyone picks up a tool. The details live on our pricing page.

A note on older Akron and Wadsworth homes

A lot of houses around here date to the 1950s through 70s, and plenty still have their original chrome-plated brass traps. Those corrode from the inside out, so a trap that looks fine can crumble in your hand the moment you loosen the slip nut. If that happens, don’t fight it. Swap the whole assembly for PVC, which doesn’t corrode and costs less than the brass did.

Fixed it, or ready for backup?

If the drip stopped, good work. Keep an eye on the cabinet for a day or two to make sure it holds. If it didn’t stop, or the problem turned out bigger than a slip nut, our kitchen plumbing team handles under-sink repairs all over Summit and Medina counties. Family-owned in Wadsworth, 17,000+ jobs since 2009, and you can book online in about a minute.