This unit will detect water and sound an audible alarm (110db) when as little as 1/32" of water reaches the sensor. The alarm can be used as a self contained unit, or the sensor can be slid out of the case for remote mounting with the 6 ft attached cord. Use wherever there is a risk of water damage (utility rooms, laundry areas, basements, washer pans, water heater pans, secondary condensate pans, etc.) Requires 9v battery.