Channel lock pliers
Use it for: To loosen and tighten the drain nut and pivot hardware under the sink.
Shop channel-lock pliersBathroom sink drain repair
Bathroom Sink Drain Leaking? Replace the Pop-Up Flange Gasket
If the sink leaks at the drain body with the basin full, the flange gasket is a likely fault. Confirm first, then replace the gasket with a matching kit.
A focused gasket replacement usually takes one service cycle if you work cleanly, support the drain parts, and test with a full-basin fill at the end.
Before you start: Match the drain opening size, gasket shape, and thread pattern on the drain body before ordering.
How this repair starts
A focused gasket replacement usually takes one service cycle if you work cleanly, support the drain parts, and test with a full-basin fill at the end.
Safety first
- Wear gloves if the old drain has sharp corrosion or rough metal edges.
- Work slowly under the sink so you do not slip with pliers in a tight cabinet.
- Do not overtighten the drain locknut. Too much force can crack porcelain or distort the seal.
- Keep a bucket under the work area because leftover water in the drain parts can spill when you loosen them.
Tools you may need
Adjustable wrench
Use it for: To hold fittings steady while you loosen or snug nearby nuts.
Shop an adjustable wrench
Bucket or shallow pan
Use it for: To catch water left in the trap or drain parts when you take them apart.
Shop a drain catch pan
Putty knife or plastic scraper
Use it for: To remove old putty, grime, or gasket residue from the sink and flange.
Shop a plastic scraper
Clean rag or paper towels
Use it for: To wipe parts dry so the new gasket seats cleanly and you can spot fresh leaks.
Shop shop towels
Flashlight
Use it for: To see the drain body, locknut, and any active drips under the sink.
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Step-by-step fix
Step 1: Confirm the flange gasket is the leak source
- Dry the sink basin, the drain flange, and the area under the sink with a rag.
- Put the stopper down and fill the sink with a few inches of water.
- Watch for water appearing around the drain opening in the basin or dripping from the upper drain body under the sink.
- If needed, wipe everything dry again and repeat so you can tell whether the leak starts at the drain seal instead of the supply lines, trap, or faucet.
If it works: You confirmed the leak starts at the sink drain seal area, which makes the flange gasket a likely cause.
If it doesn’t: If the leak comes from the faucet, supply tubes, shutoff valves, trap joints, or the sink bowl itself, fix that problem instead of replacing the flange gasket.
Stop if:
- The sink bowl is cracked around the drain opening.
- The drain body is badly corroded, split, or missing threads.
- The leak source is unclear even after drying and retesting.
Step 2: Set up the sink and remove the pop up linkage
- Clear out the cabinet so you can work directly under the drain.
- Place a bucket or shallow pan under the drain assembly.
- Turn off the faucet so no one uses the sink while it is apart.
- Unscrew the pivot rod nut on the back of the drain body, slide the pivot rod out, and lift the stopper out from above if your pop up uses a standard rod linkage.
If it works: The sink is prepped, protected from drips, and the stopper linkage is out of the way.
If it doesn’t: If your stopper will not come free, look for a retaining clip or horizontal pivot rod still holding it in place and remove that first.
Stop if:
- The pivot hardware is frozen and the drain body starts twisting in the sink.
- You find hidden water damage or rotted cabinet material under the drain.
Step 3: Loosen the drain and remove the old gasket
- From under the sink, loosen the large drain locknut that clamps the drain body to the sink.
- Support the drain body with one hand so it does not drop or chip the sink finish.
- Push the drain body up slightly and lift the flange out from the top of the sink.
- Remove the old flange gasket or sealing washer from the drain body and note how it was positioned.
- Scrape away old putty, residue, and buildup from the sink drain opening and the flange surfaces.
If it works: The drain is apart and the old gasket is removed with the sealing surfaces cleaned.
If it doesn’t: If the locknut will not loosen by hand tools, apply steady pressure instead of jerking it, and hold the drain body so you do not crack the sink or twist connected piping.
Stop if:
- The sink drain opening is chipped enough that the new seal will not sit flat.
- The drain assembly is too corroded or damaged to reuse safely.
Step 4: Install the new flange gasket and reassemble the drain
- Compare the new gasket to the old one to make sure the size and shape match.
- Set the new gasket in the correct position on the drain body or under the flange, matching the original layout.
- Lower the flange back into the sink opening and center it so it sits flat.
- From below, reinstall the washer and locknut pieces in the same order they came off.
- Tighten the locknut until the drain feels snug and stable, but do not overtighten and distort the gasket or crack the sink.
- Wipe away any squeezed-out residue and make sure the flange stays centered in the opening.
If it works: The new gasket is installed and the drain is reassembled squarely and snugly.
If it doesn’t: If the flange shifts, loosens, or will not sit flat, take it back apart and check for leftover debris, a flipped gasket, or mismatched parts.
Stop if:
- The sink surface around the drain flexes or sounds stressed while tightening.
- The new gasket clearly does not fit the drain body or sink opening.
Step 5: Reconnect the stopper and check alignment
- Drop the stopper back into the drain from above.
- Slide the pivot rod back into the drain body and through the stopper hole, then reinstall the pivot nut.
- Reconnect any clip or lift rod linkage you removed earlier.
- Run the stopper up and down a few times to make sure it opens and closes smoothly.
- Snug the pivot nut enough to prevent drips while still allowing the rod to move freely.
If it works: The stopper works normally and the drain assembly is back together.
If it doesn’t: If the stopper does not seal or lift correctly, adjust the linkage length or reseat the pivot rod through the stopper hole.
Stop if:
- The pivot ball seal is leaking or broken and needs separate replacement.
- The drain body rotates in the sink when you reconnect the linkage.
Step 6: Test the repair with real use
- Dry the basin and the entire drain assembly again so fresh leaks are easy to spot.
- Close the stopper and fill the sink with several inches of water.
- Let it sit for a few minutes while checking under the sink for drips around the flange area and pivot nut.
- Release the water and watch the drain while it empties, since some leaks only show during flow.
- Wipe once more and recheck after a normal hand-washing or tooth-brushing use.
If it works: The sink holds water, drains normally, and stays dry around the flange and under the sink.
If it doesn’t: If it still leaks from the same area, disassemble the drain again and check for a crooked flange, debris on the sealing surface, a damaged drain body, or the wrong gasket.
Stop if:
- Water is now leaking from a cracked sink, split drain body, or damaged threaded connection.
- Repeated reassembly does not stop the leak, suggesting the full drain assembly should be replaced.
Replacement Parts
Find a bathroom sink pop up drain flange gasket on Amazon
Match the drain opening size, gasket shape, and thread pattern on the drain body before ordering.
As an Amazon Associate I earn from qualifying purchases. Repair Riot may earn a commission at no extra cost to you.
Verify the repair
- The sink can hold standing water without dripping under the drain.
- The flange sits flat and does not spin loosely in the sink opening.
- The stopper opens and closes normally after reassembly.
- No fresh water appears around the pivot nut, locknut, or upper drain body during draining.
FAQ
How do I know the flange gasket is bad?
A bad flange gasket usually shows up as a leak around the drain opening or from the upper part of the drain body under the sink when the basin is holding water. If the leak only happens at the trap or supply lines, the gasket is probably not the issue.
Do I need to replace the whole pop up drain assembly?
Not always. If the drain body threads are in good shape and the metal is not cracked or badly corroded, replacing the gasket may be enough. If the assembly is damaged, replacing the full drain is the better repair.
Should I use plumber's putty too?
Many sink drains use putty or another seal at the flange along with the gasket below. Reassemble the drain the same way the original seal was set up, and make sure all old residue is cleaned off first.
Why does the sink still leak after I changed the gasket?
The most common reasons are a crooked flange, leftover debris on the sink surface, a mismatched gasket, a damaged drain body, or a loose pivot nut or locknut. Taking it back apart and checking the sealing surfaces usually finds the problem.
Can I use the sink right away after this repair?
In most cases, yes, once the drain is fully reassembled and passes a fill-and-drain leak test. Start with a careful test first so you know the seal is holding before regular use.