Is the entire length of the cable sensor able to detect water?

Yes, the entire 4 feet cable (or 1.2 meters) sensor detects water. Additional cable sensors can be added for a maximum sensing distance of up to 500 feet or 150 meters. The cable sensors need to be connected to each other, please make sure that each cable is installed correctly. You may test each cable sensor section by inserting each cable sensor section into the Water Leak Detector separately and by pouring water on the applicable cable sensor section to test. If the cable sensor does not trigger the buzzer alarm after pouring water on the cable sensor, please contact the Lyric toll free Customer Care phone line, 1-800-633-3991.