Kiril, there is nothing perfect in this imperfect world. Some water dust in sidewalks, complicated landscape, etc. and we have rust stains. Moreover rust in valves, sprinkler heads and other parts of irrigation system is not very good. Switching to drip irrigation is not solution here. Drip system is not durable and with high iron content in irrigation water things become even worse (replace drippers and driplines every second year?). Yes there is number of such filters. Gotta choose one. Very straightforward and fundamental solution.