Abstract

A pump (B) pumps water from a swimming pool (A) to a forward/reverse direction control valve (D). The control valve (D) has a first or forward flow state in which it channels water into an inlet (20) of a filter (C) and from a filter outlet (24) back to the swimming pool and a second state in which it channels the water into the fluid outlet (24) and from the fluid inlet to a drain (28). A microprocessor based electronic control circuit (E) selectively actuates the pump at preselected intervals for preselected durations such that the water from the swimming pool is intermittently filtered. The control circuit further monitors the fluid pressure with a low pressure limit switch (46). In response to the pumped fluid pressure failing to achieve a low limit within a preselected duration, the control circuit terminates operation of the pump. Further, the control circuit monitors the water pressure with a high pressure limit switch (48). In response to the monitored pressure exceeding the high limit, the control circuit causes the forward/reverse valve (D) to assume its second state and backwash the filter automatically. The microprocessor also calculates the volume of fluid discharged through a drain, which is automatically replaced with fresh fluid.