Displays TDS level of a single water line. Highly efficient and accurate due to its advanced microprocessor technology. The unit shuts off after 10 minutes of non-use to conserve battery life. Wide Range 0-9990 ppm (from 0-999 ppm resolution is 1 ppm. From 1000 to 9990 ppm, resolution is 10 ppm, indicated by a blinking 'x10' image.) Factory calibrated with a 342 ppm NaCl solution. Can be recalibrated with a mini-screwdriver. Comes with John Guest quick-connect tee (1/4 inch standard).