Possible cause: grime on the stopper

Why this happens

Kohler describes its strainer basket as one with an open and close stopper that seals tightly into the strainer body, and Bob Vila says that for bathroom sink stoppers, cleaning the parts can often fix a stopper that is not sealing properly. Bob Vila's article is about bathroom pop-up stoppers, so treat cleaning as a general tip that costs nothing to try, not a promise that it will fix your drain.

How to fix it

1. Check the cabinet under the sink before you add any water. This page is for a bowl that loses water down the drain while the cabinet stays dry. If anything under the sink is wet or dripping, do not add water and use the kitchen sink guide again, then choose the wet cabinet answer. If a plug, cord or outlet under the sink is wet, do not touch it and call an electrician. Turn off the breaker only if you can reach the panel safely. If you cannot, stay away from the area and call an electrician or emergency services.
2. Keep the faucet off. If this bowl has a garbage disposal, shut off its power first, by unplugging it or turning off its breaker, as Waste King describes before removing a stopper. If the disposal has no wall switch and starts when a stopper is set in the opening, Waste King calls that a batch feed type, so keep its power off for the whole job. Keep your fingers out of the opening. Waste King says never to place your hand inside the disposal.
3. Lift the stopper or basket straight out. Danco says the knob on its basket is twisted to let water drain and lifted to take the basket out.
4. If it will not come out, do not force it. Bob Vila's article on bathroom sink stoppers warns that too much force can damage a sink, and the same care makes sense here. Stop here and call a plumber.
5. Scrub the stopper and its rubber seal with a soft brush and a mild cleaner or vinegar, as Bob Vila suggests for bathroom stoppers. Clean only the stopper and its rubber seal, and leave the drain opening alone. Use one cleaner at a time.
6. Look at the rubber seal or O-ring. Family Handyman says a twist-and-drop style basket needs its O-ring replaced from time to time. If the rubber looks damaged, go back one step and choose the answer about a torn or missing seal.
7. Set the stopper back, fill the bowl a few inches and watch the water level for several minutes.

When to stop. If the stopper is stuck, the drain body looks cracked or loose, or the bowl still empties after a clean stopper is back in, stop and call a plumber. Do not force a stuck stopper.

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