Fixing a Leaking Kitchen Sink Drain with New Putty and Washers

A slow leak around the left-side drain of a kitchen sink turned up while preparing to install a new faucet. Wetness near the sink seal and long-term water damage on the bottom of the cabinet pointed to the drain strainer, and the repair needed only a screwdriver and channel lock pliers.

Finding the leak

The water was visible around the sink seal at the drain, with wetness below. No drip was seen while the cabinet was open, but the area felt damp.

Taking it apart

The first step is closing the cold and hot shut-off valves, turning them right to close. A separate valve feeding the dishwasher was left on. The P-trap and drain pieces are hand-tightened and come off by spinning them with your fingers. The P-trap holds water as a barrier against vapour from the drainage system, so a container goes underneath first. A flathead screwdriver loosens a hose clamp, and channel locks loosen the metal nut at the top of the strainer.

What failed

With the strainer out, the plumber's putty around the rim was cracked, which was probably causing the leak. The washer was also not seated properly. Two items were bought: fresh plumber's putty, because the old tub had dried up, and sink strainer washers. The set has a black rubber washer and a friction washer that goes below it against the rim.

Rebuilding the seal

The top and underside lip of the drain are cleaned, and a scrub pad cleans the lower piece. The putty is rolled into a snake, one long bead, and pinched at the join so there is no seam. It is pressed down evenly. If no putty squeezes out, not enough was used. The video says about half of what was used would have been enough. The friction washer and then the rubber washer go on, spaced evenly, and the nut is tightened with channel locks until snug.

Reassembly and checking

The drain pieces and P-trap go back on and are tightened only to snug, so the next person can remove them easily. Excess putty on top is removed with fingers and then a kitchen or table knife. After the water is turned on, all pipes should be dry. A week later, a recheck is recommended, and an empty catch basin can be left underneath to reveal any drip.