Kitchen Sink Leaking Around the Drain? The Seal Most People Skip
Most leaks at the drain come from a dried-out putty seal or a loose locknut under the basket. Reseal the strainer and the drip stops.
By Jamilur Rahman Updated November 5, 2026 · 7 min read
- Time
- 45 min
- Cost
- Under $20
- Difficulty
- Medium
In this guide
Quick answer
If your kitchen sink keeps leaking around the drain, the cause is usually a dried-out putty seal, a worn gasket or a loose locknut under the strainer basket. Dry everything, run water to find the true source, then remove the strainer and reseal it with fresh plumber's putty and a new gasket. If the water comes from a pipe joint or the faucet instead, the fix is different.
Free fix vs. permanent fix
Dry it, find the source, and snug the nuts
- Dry the area and run water to find the real source
- Hand-tighten the slip nuts by a quarter turn
- Snug the locknut under the basket
- Do not crank plastic nuts with a wrench
How long it lasts: Good if a nut was only loose. If the putty has dried out or the gasket has hardened, the drip comes back within days.
A new strainer basket kit with a gasket
The drain seal sits between the sink and the strainer. Once the putty dries and the gasket hardens, tightening cannot fix it. Resealing with fresh putty and a new gasket restores the seal.
What to get: Kitchen sink strainer basket kit with gasket and locknut
How long it lasts: Years. A fresh seal keeps water above the basket and out of the cabinet.
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What you'll need
-
Bucket and towels
Catch water and dry the area
You have it -
Channel-lock pliers
Loosen and tighten the locknut and slip nuts
You have it -
Plastic scraper or putty knife
Removes old putty without scratching the sink
You have it - Our pick Illustration
Sink strainer basket kit with gasket
Includes the gasket and locknut
- Illustration
Plumber's putty
Seals the flange to the sink
Why it happens
Dried-out plumber's putty
Putty under the strainer flange stays soft for years, then hardens, shrinks and cracks. Water slips past it into the cabinet.
A hardened or flattened gasket
The rubber gasket under the sink compresses and hardens with age, so it no longer grips the underside of the basin.
A loose locknut
Vibration and temperature changes can loosen the nut that clamps the strainer to the sink.
A crack in the strainer or the sink
A cracked basket, or a hairline crack in the sink, leaks no matter how tight you make the nut.
A leak that only looks like a drain leak
Water runs along pipes, so a drip at the drain may begin at a slip nut or the faucet. A dry-towel test shows where it starts.
Try this first (free)
Do these in order, starting with the simplest.
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Clear the cabinet and dry everything
Tool used: Bucket and towelsEmpty the space under the sink and put a bucket under the trap. Dry the basket, the nuts and the pipes with a towel. A dry surface shows exactly where new water appears.
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Run water and watch for the first drop
Fill the sink a few inches, then pull the stopper. Hold a dry paper towel against each joint. The first spot that gets wet is the source.
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Tighten by hand first
Tool used: Channel-lock pliersHand-tighten the slip nuts on the trap by a quarter turn. For the locknut under the basket, give it a quarter to half turn with channel-lock pliers. Stop when it is snug.
-
Remove the strainer and scrape off the old putty
Tool used: Plastic scraper or putty knifePut a bucket under the drain, unscrew the locknut and lift the basket out from above. Scrape the old putty off the sink with a plastic scraper, then wipe the area clean and dry.
-
Reseal with putty and a new gasket
Tool used: Sink strainer basket kit with gasketRoll a rope of putty about 1/2 inch thick and press it under the flange. Seat the basket in the drain hole. From below, fit the new gasket and friction ring, then tighten the locknut. Wipe off the squeezed-out putty.
IllustrationCheck price on AmazonTool for this step
Sink strainer basket kit with gasket · Includes the gasket and locknut
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Test with a full sink
After the time listed on the putty pack, fill the sink, pull the stopper and check every joint with a dry paper towel. Check again after an hour.
When free fixes aren't enough
Tightening only helps when a part is loose. If the putty has dried, the gasket is flat or the strainer is corroded or cracked, you need a fresh seal and often a new basket. Call a plumber if the cabinet base is soaked and soft, if the leak comes from the supply lines or faucet and you cannot stop it, or if the pipes are old and corroded. If the leak is near a garbage disposal's power connection, switch off the power to the disposal before you work near it.
Buy the fix
Still stuck after the free fixes? These are the products we would look at.
| Pick | Product | Fixes | Who it's for | Buy |
|---|---|---|---|---|
| Best pick | Kitchen sink strainer basket kit with gasket and locknut | a leak where the strainer meets the sink | Anyone whose strainer is old, corroded, wobbly or has leaked more than once. | Check price |
| Budget pick | Plumber's putty | a dried-out seal under a strainer that is otherwise in good shape | People whose strainer is fine and only the seal has failed. | Check price |
| Upgrade pick |  Kitchen sink trap kit with slip-joint washers | leaks at the trap and slip joints below the basket | Owners whose leak turns out to be at the pipe joints. | Check price |
Kitchen sink strainer basket kit with gasket and locknut
Fixes: a leak where the strainer meets the sink
Look for: Fits your sink's drain opening, usually 3-1/2 inches, so measure first; A solid metal body with the rubber gasket and locknut included; A finish that matches your sink and faucet.
- Who it's for
- Anyone whose strainer is old, corroded, wobbly or has leaked more than once.
- Honest downside
- You have a garbage disposal on the drain. It uses a different flange kit.
Plumber's putty
Fixes: a dried-out seal under a strainer that is otherwise in good shape
Look for: Soft, pliable putty that has not dried out; A label for sink drain use; A non-staining formula if your sink is stone or solid surface.
- Who it's for
- People whose strainer is fine and only the seal has failed.
- Honest downside
- The sink is natural stone, or the strainer is plastic. Check the maker's instructions, because silicone may be the better seal.
Kitchen sink trap kit with slip-joint washers
Fixes: leaks at the trap and slip joints below the basket
Look for: Matches your pipe size, with 1-1/2 inches common for kitchen sinks; New washers and slip nuts included; Plastic or metal to match your existing pipes.
- Who it's for
- Owners whose leak turns out to be at the pipe joints.
- Honest downside
- The leak is at the strainer. Start there instead.
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How we picked: How we picked: this page is based on plumbing guides for kitchen drains, the instructions from strainer and putty makers, and what owners report in reviews. We do not test products by hand.
Why is my kitchen sink leaking underneath? Find the source first
The water you see may not start where you see it. Dry everything, then run the sink and test each spot.
- Leaks while the sink fills: the strainer basket or the overflow.
- Leaks while it drains: the trap and slip joints.
- Leaks when the faucet runs: the faucet base or the supply lines.
Have a garbage disposal? It changes the repair
With a disposal, the sink flange is held by a mounting assembly, not a simple locknut. Switch off the power to the disposal before you start. If the leak comes from the disposal body, see the related page on disposal leaks.
What to skip
Caulk over the leak and brute-force tightening
Caulk smeared on the outside seals nothing, since the water comes from between the basket and the sink. Over-tightening plastic nuts cracks them. Tape on pipes is a short-term patch at best. If the drip stays, reseal the strainer properly.
Frequently asked questions
How to stop a kitchen sink drain from leaking?
How to stop kitchen sink pipes from leaking?
Why does my kitchen sink keep leaking after I tightened it?
How to fix a kitchen sink leak, and when do I call a plumber?
How to stop a kitchen sink from leaking: does it leak when full or when draining?
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