Water Softeners and Air Filtration Systems - Kenmore Sears Iron Removal System Not Working

Our house has Sears Iron removal system. Not working properly. have cleaned orfice and screen, installed new Potassium Permangnate. Had renters for a year and they turned valves and had water bypassing the iron remover. I suspect water heater is contaminated(water is gray). Cold is clear but still has odor. We have a service agreement. They installed a new circuit card in timer figuing it wasn't cycling properly. They have serviced 4 times over the past year and still isn't repaired. Seems service techs don't know much about it? Tennants moved out and left badly rust stained sinks, shower, tile and commodes. It worked pretty well when we lived there. Should I replace it with another brand? General Ionics or Culligan. Or should I insist that Sears replace it. Only 4 or 5 years old? Help, fellows?

ol' guzda in the mountains of SW PA