Hi Ronald,
Personally I have grown citrus plants/trees in AutoPot for many years in greenhouses and outside with no issues at all, the growth is fantastic, we simply used a citrus feed and have never encountered any issues with salts and rain washing them down. We would suggest that if you have AutoPot outside that if it rains heavily and for longe periods simply turn off the reservoir and then turn it back on when the rain has subsided and the solution in the tray has been consumed.