Having sprinkler systems installed while living in South Florida is pretty common, however having brown iron spots covering the outside of your siding is not exactly what homeowners are happy to see when living there.
Where does this brown coloring on siding coming from? The answer is from the hard water inside the sprinklers. The mineral filled water hits the siding on your house and although it seems harmless at first, it will start to produce more and more iron stains.
A local woman named Karen Clarke had this very issue at her condo. Her sprinkler was set to spray only the grass but somehow had gotten turned which made it begin hitting the home instead. The article done by WSVN gives further details on this occurrence. Reynolds Water Conditioning Company specializes in these hard water needs and has options available such as Irrigation Stain Control Systems to help provide prevention from such hard water stains from occurring in the first place.