Bathroom sink stopper won't hold water

A bathroom sink that slowly empties with the stopper closed usually comes down to the linkage under the sink, a dirty or worn stopper seal, or the seal where the drain meets the sink. Let's figure out which one you have. Fill the sink a few inches and answer a few questions while you look.

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Before you start. Before you open the drain, let the sink empty, keep the faucet off and set a bucket under the drain pipes. If a chemical drain cleaner has gone down this sink, do not open the drain. Family Handyman says leftover caustic chemicals are a danger to anyone who takes the trap apart. Call a plumber and say what you used. If the drip under the sink is on a water supply line or a shutoff valve and it will not stop, close the main shutoff and call a plumber.

A white bathroom sink full of clear water with the pop-up stopper closed and the lift rod behind the faucet

How the lift rod moves the stopper

Every question and answer on this page, in order

Question 1: Close the stopper and fill the sink a few inches. Where does the water go?

Lay a dry towel on the cabinet floor under the sink first, then check it after a few minutes.

Down the drain. The cabinet under the sink stays dry: go to question 2
Under the sink. I see drips or a wet towel: go to question 3

Question 2: How do you close this drain?

A lift rod is the small rod or knob behind the faucet that you pull up. Bob Vila describes the other common type as a stopper you push down to close and push again to open, with nothing connected to it under the sink. Family Handyman describes two more types, lift and turn and flip top, which this page does not cover.

I pull up a lift rod behind the faucet: go to question 4
I push down on the stopper itself: Likely cause: debris in a push-to-close stopper

Question 3: Dry the drain parts under the sink with a towel and keep the sink filled. Where does the first drip form?

Pfister's leak check is the same idea: stopper the drain, fill the sink, and look underneath. If the first drip is on a water supply line, a shutoff valve or the faucet connections, it is not the drain, so use the faucet leaking at the base troubleshooter instead. If it is lower down, at the trap or a pipe joint, that is a drain pipe leak and not a stopper problem. Keep a bucket under it and call a plumber.

At the small nut on the back of the drain pipe, where the horizontal rod goes in: Likely cause: a loose or disconnected pivot rod
Higher up, where the drain meets the bottom of the sink: Likely cause: a leak where the drain seals to the sink

Question 4: Pull the lift rod all the way up and watch the stopper. What does it do?

Delta notes that the cap on its stoppers is not designed to sit flush with the drain flange. Watch for the stopper dropping, not for a perfectly flat fit.

It stays up or partly open, or it does not move: go to question 5
It drops and looks closed, but the water still drains away: go to question 6

Question 5: Look under the sink at the horizontal rod coming out of the back of the drain pipe. What do you see?

This Old House describes the parts this way: the lift rod fastens to a flat metal strap with a row of holes, a horizontal pivot rod passes through one of those holes and is held by a spring clip, and the other end of the pivot rod goes into the drain through a nut.

The rod is clipped to the strap and nothing is loose: Likely cause: the lift rod linkage needs adjusting
The rod has slipped off the strap, or the nut or screw is loose: Likely cause: a loose or disconnected pivot rod
The rod is broken or badly rusted, or it moves but the stopper does not: Likely cause: a broken or corroded pivot rod

Question 6: With water in the sink, press down firmly on the closed stopper with your hand. Does the water still drain away?

Delta suggests this check to tell a stopper problem from a leak around the drain flange.

No, it holds while I press: go to question 7
Yes, it still drains away: Likely cause: a leak where the drain seals to the sink

Question 7: Lift the stopper out and look at the rubber seal under its cap. What do you see?

Danco says some stoppers simply lift out. If yours will not, pick the last answer and the result page shows how to free it.

Hair, soap scum or grit on the stopper or around the drain opening: Likely cause: hair and buildup on the stopper seal
The rubber seal is cracked, brittle, torn or missing: Likely cause: a worn or damaged stopper seal
The seal is clean and looks sound: Likely cause: the lift rod linkage needs adjusting
I cannot get the stopper out: Likely cause: hair and buildup on the stopper seal

Possible results

Need the words for the phone call? Build a what-to-tell-the-plumber checklist, or read when to call a plumber.