A sensor system for swimming pools and spas is detailed herein. The sensor system can include one or more sensors positioned in a sensor housing located within a cavity of a pipe and in-line with an inlet and an outlet of the pipe. The sensor housing can divert a portion of water flowing through the cavity to an interior of the sensor housing and to an area around the sensors and maintain at least some of the diverted water in the area around the sensors even if the water is not flowing through or is drained from the pipe.