all-sun Portable Water Leak Alarm Leak Detector Water Damage Tester Flood Sensor Power supplied by 3 pieces 1.5V AAA battery.Not Provided by seller Replace the batteries and test the unit at least once half a year for proper operation. In any situation, the height of water surface must not exceed 5mm,otherwise water will get into the unit and cause damage. Do not let water(or liquid) flow into buzzer hole to avoid damage.