Kitchen sink leaking underneath — Krakow, Lesser Poland

Water pooling inside the cabinet beneath a kitchen sink is one of the most common plumbing problems in any home, and because it is hidden behind cabinet doors, it often goes unnoticed until mold, warped wood, or a musty smell gives it away. The leak can originate from several points: worn-out compression fittings or corroded shut-off valves on the hot and cold supply lines, loose slip-nut connections on the P-trap or tailpiece, a failed gasket between the sink basin and the drain flange, or cracked seals around a garbage disposal unit. Even a slow drip — just a few drops per minute — can saturate the cabinet floor, delaminate particleboard, and create an ideal environment for mold growth within days. A plumber can typically diagnose and repair the leak in under an hour ($150–$300 for a service call), with parts rarely exceeding $30–$50. Replacing corroded supply lines with braided stainless-steel hoses ($10–$20 each) during the repair is a smart preventive upgrade.