You can clean them off with a rust remover made for the surface. But they’ll come back unless you stop the iron water from reaching the wall. Here’s how to confirm the cause, what to use on stucco, brick and siding, and what to ask a pro.

Why well water paints your walls orange

Groundwater is usually low in oxygen, so iron from soil and rock dissolves into it. Once that water meets air, the iron oxidizes and turns from a clear, dissolved form into colored particles. Every time the water dries on your wall, it leaves a little more behind.

A University of Georgia water guide says staining is likely once iron reaches 0.30 mg/L. In a large federal survey of the Upper Floridan aquifer, about 15 percent of drinking-water wells were above that level. A UF/IFAS landscaping program goes further and says most Florida well water is high in iron. It names orange streaks on the sides of buildings as a common result.

The question comes up in Florida communities, too. In The Villages, a homeowner with light brown stucco asked a local forum how to remove sprinkler overspray stains. He had already adjusted the heads, and neighbors traded product names.

Is it rust, or just wet?

Before you buy anything, look at the wall when it’s bone dry. Brick soaked by a sprinkler can look discolored while it is still wet. If you got an HOA letter about “discoloration,” our HOA notice checklist walks through that first step.

A true iron stain is orange to reddish brown and stays put after the wall dries. Stains that line up with where the spray lands point to the sprinklers. Dark gray or black marks can point to manganese, which often travels with iron. If you’re seeing orange dots on the driveway after a lawn treatment instead, that’s a fertilizer problem, covered in rust spots after a lawn treatment.

Skip the bleach

A University of Georgia guide says iron stains are hard to remove with common household cleaners. It adds that chlorine bleach combined with high-iron water will permanently stain laundry. So skip the bleach, and don’t expect a mildew-focused house wash to lift rust on its own.

What to use on each surface

Always test on a hidden spot first. The table names products only so you can find the directions we quote; it is not an endorsement.

Surface What a label or guide says to use Key cautions from the source
Unpainted, unstained concrete or similar masonry Rust Aid Outdoor Rust Remover: apply full strength, let the stain disappear, rinse thoroughly, repeat if needed Do not use on painted, stained or pigmented surfaces; wet nearby plants before and after; etches glass if not rinsed
Brick GSA preservation procedure for light rust stains: oxalic acid, 1 part powder to 10 parts water by weight, brushed or sprayed on Oxalic acid is toxic and corrosive to concrete, steel, wood and glass; keep it off windows and trim
Vinyl siding Rust Free (The Rust Store): spray on, wait 30 seconds to a minute, wash off Test on an inconspicuous spot first; wear eye protection and gloves

Painted or tinted stucco is the tricky one. The outdoor remover’s label says not to use it on painted, stained or pigmented surfaces, so a pro test patch is worth it there. If you’re unsure whether a cleaner already marked the wall, see how to tell wash damage from damage that was already there.

Stop it at the source

Cleaning without fixing the water is a repeat bill. Start with these, cheapest first.

  • Re-aim the heads. EPA’s WaterSense program asks whether you’re watering the driveway, house or sidewalk instead of the yard. Point heads away from walls, or shorten their throw.
  • Test the water properly. Penn State Extension found a rust-colored sample read under 0.1 ppm iron when filtered, but 48.5 ppm when tested unfiltered and acidified. Ask the lab for total iron, and test for manganese too. Your county extension office can point you to a lab.
  • Treat the irrigation water. UF/IFAS lists water softeners, oxidizing filters and combined chlorination and filtration as options, depending on the iron level. Match the system to your test results.

Hiring someone to clean it

A pro can save you from handling acids on a two-story wall. Ask these questions before you book:

  • Which rust remover will you use, and is it safe for my surface (painted stucco, brick, vinyl)?
  • Is rust treatment priced separately from the house wash?
  • What water will you rinse with? A washer on a trade forum described cleaning with a property’s high-iron well water and seeing stains return within three days.
  • How will you protect plants, windows and the lawn?

Our questions to ask a house washing company cover insurance and the rest of that call. For typical prices, see what house washing costs. For how we source and check every claim, see our methodology.

Sources