I have a 4 and half year old pool with a MagnaSweep in floor cleaning system. In the last week or so one zone of heads does not shut off completely. The control valve has flapper valve not balls in it. I checked all the flappers and can find nothing wrong. I called A&A manufacturing but they were no help. The guy I talked to, had no clue about the problem. Buy the way, the one part that you would think was repairable( the flappers ) are not replaceable. Any Ideas?