Designed to prevent the whirlpool pump from operating when there is insufficient water in the tub, the MB-LWS Low-Water Sensor is mounted on the tub approximately 1" above the highest jet.  For Classic Series tubs, the sensor will include a timer which will shut off the whirlpool pump after 20 minutes of operation.  The timer is standard on all whirlpool and air bath packages for Designer Series tubs.