Designed for use on 3/4 in PVC condensate drain line. Snaps easily over existing drain line tubing and can be glued in place using PVC cement. The SOS electronically senses water near the inside wall of the PVC drain tubing. By locating the SOS with its body away from the normal flow, it can be used to detect a possible overflow condition when the PVC drain line becomes full with water. Like a culvert, the condensate drain line is normally mostly empty with a small amount of water flowing in the lower parts of the horizontal run. Since the sensor component of the SOS only covers part of the tubing, a low volume of flowing water does not activate the switch. The pipe must be full or near full to activate the switch. Mount SOS horizontally, vertically or at any angle. Works with 24 VAC control circuits and typical contactors. When not detecting water, the SOS is normally closed and allows normal air conditioner operation. When water approaches the SOS's sensor, the switch triggers and the control circuit is opened. The LED indicator lights to show that there may be system trouble and the SOS is doing its job. Includes press to test switch. Furnished complete with switch, 5 ft (1.5 m) 18 AWG, 2 wire lead and a 3/4 in PVC male fitting adapter for direct coupling to a primary pan drain line connection. Now available with Push to Test button.