A water leakage monitoring and response system for residential and commercial use. A flexible, elongated moisture sensor strip for placement on a floor or adjacent a baseboard or plumbing fixture comprises flexible upper and lower wires separated by a water permeable, nonconductive layer, and nonconductive upper and lower layers that extend away from the wires to form margins for attaching the strip to a surface and for wicking moisture toward the wires. Alternatively, the wires are laterally spaced-apart within the strip and/or the strip assumes the form of a pad to cover a surface area. In use, a plurality of strips/pads are wired to input jacks of a battery-powered electronic interface unit that provides audible and visual signals when moisture shorts the wires in the strips/pads. The unit also provides audible warning of low-battery power and can signal a home security system when a leak is detected.