Here is a link for an inexpensive water leak detector. The company has been in business for a long time. These leak detectors are used extensively in mechanical rooms in buildings to detect water leaks on floors. The leak sensor is a 'tape' or some call it a 'rope', and can be purchased in lengths from five feet and up, giving the ability to completely surround a room. The start around $90 for a five foot sensor and the price increases for additional lengths.
Here is the link;
dwyer-inst.com
Here is the link;
Series WD Water Detector and Sensor Tape
Water Detector and Sensor Tape is designed for dependable detection of water presence even of low conductive liquids. A few applications include telecommunication facilities and computer rooms.
dwyer-inst.com
