Step-by-step fix
Step 1: Confirm the sink strainer is the leak source
- Dry the area under the sink, especially around the strainer body, locknut, tailpiece, and trap.
- Run a small amount of water around the sink opening and then drain it while watching with a flashlight.
- Check where the first drip forms. A strainer leak usually shows up at the sink opening, around the strainer body, or from the locknut area directly below it.
- Wipe the faucet supplies and drain trap connections too, so you do not mistake a different leak for a bad strainer seal.
If it works: You have traced the leak to the sink strainer area rather than another plumbing connection.
If it doesn’t: If the drip starts at a slip joint, trap nut, supply line, faucet base, or a crack in the drain piping, fix that problem instead of resealing the strainer.
Stop if:- The sink basin is cracked around the drain opening.
- The metal around the drain opening is badly rusted, distorted, or too damaged to seal reliably.
- The leak is coming from a hidden pipe in the wall or cabinet rather than the strainer assembly.
Step 2: Set up the work area and disconnect the drain below
- Clear out the cabinet so you can work directly under the drain.
- Place a bucket or shallow pan under the trap and strainer area.
- If your sink has a disposer or dishwasher connection attached to this drain, make sure the disposer cannot be switched on while you work.
- Loosen the slip nuts or drain connection below the strainer and move the tailpiece or trap parts out of the way enough to access the strainer locknut.
If it works: The drain parts below the strainer are disconnected or moved aside, and you can reach the mounting hardware clearly.
If it doesn’t: If the nuts are stuck, apply steady pressure with pliers and support the connected pipe so you do not crack it.
Stop if:- A disposer, drain arm, or trap connection is cracked or too corroded to reconnect safely.
- You cannot access the strainer hardware without forcing rigid piping enough to risk breaking it.
Step 3: Remove the strainer and all old sealing material
- Hold the strainer body from above or below as needed and loosen the large locknut under the sink.
- Remove the locknut, friction ring, and gasket in the order they come off so you can reinstall them correctly.
- Lift the strainer body out from the sink opening.
- Scrape all old plumber's putty, old sealant, grime, and mineral buildup from the sink opening and the underside of the strainer flange.
- Wipe both surfaces clean and dry. The new seal will only hold if these surfaces are smooth and clean.
If it works: The strainer is out, and both the sink opening and strainer flange are clean and ready for fresh sealant.
If it doesn’t: If residue keeps smearing, keep scraping and wiping until bare metal or clean sink surface is exposed all the way around.
Stop if:- The strainer body is cracked, badly pitted, bent, or missing parts needed to clamp it evenly.
- The sink opening is warped enough that the flange cannot sit flat.
Step 4: Apply fresh sealant and reinstall the strainer
- Roll plumber's putty into a rope and press it under the strainer flange, unless your strainer uses a different sealing method specified by its parts layout.
- Set the strainer into the sink opening and press it down evenly so the flange sits flat.
- From below, reinstall the gasket, friction ring, and locknut in the correct order.
- Tighten the locknut gradually while keeping the strainer centered and aligned.
- Do not overtighten. Tighten just enough to compress the seal evenly and squeeze a small amount of putty out around the flange.
- Wipe away the excess putty from the top of the sink.
If it works: The strainer is seated flat, tightened evenly, and sealed with fresh material all the way around the flange.
If it doesn’t: If the strainer twists, lifts, or will not stay centered while tightening, loosen it and reset it before going further.
Stop if:- The sink surface begins to flex, crack, or distort while tightening.
- The mounting parts will not thread together cleanly because the hardware is stripped or mismatched.
Step 5: Reconnect the drain and snug the joints
- Reconnect the tailpiece, trap, or disposer connection below the strainer.
- Tighten slip nuts firmly by hand first, then give them a small additional snug with pliers if needed.
- Make sure the drain parts line up naturally without side pressure pulling on the strainer.
- Wipe every joint dry so new leaks will be easy to spot during testing.
If it works: The drain assembly is back together, aligned, and dry before testing.
If it doesn’t: If the piping does not line up, loosen the joints and realign them before tightening again so the strainer is not being pulled sideways.
Stop if:- A slip nut, washer seat, or drain tube is cracked and cannot seal when reassembled.
Step 6: Test the repair under real use
- Close the stopper and fill the sink with several inches of water so the strainer seal is under pressure.
- Dry the area below one more time, then release the water and watch the strainer body, locknut area, and reconnected joints closely.
- Run more water for a minute or two and check again with a dry paper towel around the strainer and each nearby connection.
- Leave the cabinet open and recheck after the sink has drained completely.
If it works: No water appears around the strainer flange, locknut, or drain connections during filling, draining, or a final recheck.
If it doesn’t: If the leak is at the strainer, remove it and reseal it again after cleaning the surfaces more thoroughly. If the leak is at a slip joint, adjust or reseat that joint instead.
Stop if:- Water still leaks from the sink opening after a careful reseal and even tightening, which usually points to a damaged strainer or sink opening.
- A hidden leak appears elsewhere in the drain system during testing.
FAQ
Do I always need plumber's putty to reseal a sink strainer?
Many sink strainers seal with plumber's putty under the top flange, but some use a supplied rubber or foam seal instead. Use the sealing method that matches the strainer parts you have. If there is already a dedicated top gasket design, do not add putty unless the manufacturer specifically calls for it.
Why does the strainer still leak after I tightened it more?
More tightening does not fix dirty or uneven sealing surfaces. The usual cause is old putty left behind, a twisted gasket, a strainer that shifted while tightening, or damaged parts. Taking it back apart and cleaning everything thoroughly usually works better than just tightening harder.
Can I reseal the strainer without removing the drain pipes below?
Usually no. You need access to the locknut and gasket stack under the sink, so the tailpiece or nearby drain parts normally have to be disconnected or moved aside first.
Should I replace the gasket when I reseal the strainer?
If the gasket is flattened, cracked, brittle, or deformed, replace it. If it is still flexible and matches the strainer correctly, you may be able to reuse it, but a fresh gasket is often the safer choice when you already have the assembly apart.
How do I know if the sink itself is the problem?
If the drain opening is cracked, badly rusted, warped, or no longer flat, a new seal may not hold. In that case the strainer is not the only issue, and the sink or damaged drain opening area may need repair or replacement.