Water Sensor provides peace of mind. Activated when there is a flooding, prevents accidental overflow. Works with Reciever Item 300418 (sold seperately). When Water Alert Sensor is activated, it sends a signal to the receiver which provides audio beep and visual indicators. Suitable for your sump, washing-machine, hot water heater and bathtub etc. Operates on 1 CR- 2025 Lithiium Battery (included).