A control system for bathers with ground continuity and ground fault detection includes an electronic controller which controls operation of electrically powered devices such as an electric heater assembly connected in a water flow path for heating water. A solid state water temperature sensor apparatus provides electrical temperature signals to the controller indicative of water temperature at separated first and second locations on or within the heater housing. A solid state water presence sensor apparatus determines the presence of water within the heater housing, providing electrical water presence signals to the controller indicative of the presence or absence of a body of water within the heater housing. The system includes ground continuity detection, ground current detection and ground fault detection circuits. The ground continuity detector detects continuity of the electrical ground and provides an electrical detector signal to the controller indicative of a ground continuity status. The ground current detector detects a current flow in the electrical ground line and provides a detector signal to the controller indicative of the current flow detection. The ground fault detection circuitry detects a current imbalance in high power conductors, and disconnects high power outputs from the respective spa devices when a current imbalance is detected, without disconnecting power from the controller.