The Orange Stains on Your Siding Are Not Dirt

It shows up as rust-coloured arcs on the lower part of a wall, on a vinyl fence, along a walkway, or across a concrete apron — and always in the same shape, because the shape is the throw of a sprinkler head. The source is iron dissolved in irrigation water, and iron at concentrations as low as 0.3 parts per million is enough to stain. Well water on this stretch of coast frequently carries more than that.

Why washing does nothing

Ordinary exterior cleaning is built around organic growth — algae, mildew, the black on a north wall. The chemistry that kills growth does nothing at all to a mineral deposit that has bonded to a surface. This is why the stain survives a house wash and why homeowners sometimes conclude the wash was worthless. It was not; it simply addressed a different problem that happened to be on the same wall.

What removes it

An acid treatment, usually oxalic. It dissolves the iron without bleaching the surface underneath or etching vinyl, which is why it is the standard in the trade rather than something harsher. It should be a separate line on a quote, because it is separate work — and if it is not on the quote, it is not being done.

Why it keeps coming back

Because the sprinkler is still running. Cleaning treats the symptom; the iron arrives again next season. There are two real fixes and both live upstream of any cleaning contractor: adjust or move the heads so they stop hitting the house, fence and hardscape, or treat the water. Homeowners running irrigation off a well generally end up on a yearly cleaning cycle; properties on municipal supply, with a far lower iron load, can usually stretch to eighteen months or more.

Where this turns up most on the island

Anywhere irrigation is common and the heads are close to the house — the interior streets of North Beach Haven and the larger lots at the north end are where it is most often seen. If your neighbours' houses have the same orange arcs at the same height, that is the answer confirmed.

The one that cannot be fixed

Hard-water spotting on glass is the same family of problem, and if it has been left long enough it etches. At that point no cleaner removes it, because the mineral has taken the surface of the glass with it. Windows in the arc of a sprinkler head are worth rescuing early.