How to Fix a Leaking Kitchen Sink Basket Strainer

Diagnosing the Leak

Fill the sink with water, then watch underneath for drips. If water drips from the strainer body where it passes through the sink, the putty seal has failed. If water drips from the connection between the strainer and the tailpiece below, the slip nut connection needs attention. Place a paper towel directly under the strainer body and another under the tailpiece connection to pinpoint the exact leak location. This distinction is important because each leak requires a different repair approach.

Re-Tightening the Strainer

Sometimes the fix is as simple as tightening the locknut. From underneath the sink, use a strainer wrench or large channel-lock pliers to turn the locknut clockwise (when viewed from below). Have someone hold the strainer from above so it does not spin. If you can tighten the locknut and the leak stops, the putty just needed more compression. Test by filling and draining the sink. If the locknut is already tight and the leak persists, the putty has dried out and the strainer needs to be removed and resealed.

Resealing the Strainer

Remove the strainer by loosening the locknut from below. Lift the strainer out from above and scrape all old putty from both the strainer flange and the sink surface. Clean both surfaces with rubbing alcohol for a contaminant-free bonding surface. Apply a fresh rope of plumber's putty around the strainer flange or, for granite and stone sinks, use silicone sealant (plumber's putty can stain porous stone). Reinstall the strainer and tighten the locknut firmly.

Fixing the Tailpiece Connection

If the leak is at the tailpiece slip joint connection, disconnect the tailpiece slip nut. Inspect the nylon or rubber slip washer — if it is cracked, compressed flat, or deformed, replace it. Clean both the strainer tailpiece and the inside of the slip nut. Install a new slip washer with the tapered side facing up (toward the strainer). Reconnect and hand-tighten the slip nut, then give it a quarter turn with pliers. Over-tightening can crack the nut or deform the washer, causing a worse leak.