An improved spa control system is disclosed. The invention describes a spa control system which calculates the time required to heat the water in the spa system to a desired temperature. From that information, the heating rate of the spa system can be determined, and the heating element of the spa system can be activated at the proper time to raise the temperature of the water to a selected temperature by a desired time. The spa system also monitors information which might show errors in the operation of the spa system such as a blockage in the flow of water over the heating element in the spa system.