What the white streaks are
Local water carries dissolved calcium and magnesium. When it lands on a surface and evaporates, the water leaves and the minerals stay. Repeat that daily for a few years and you have a bonded crystalline deposit — chemically closer to soft rock than to dirt.
Why normal cleaning does nothing
Detergents lift oils and organic matter. Mineral deposit is neither. You can scrub indefinitely with a general-purpose cleaner and make no impression, because you are attacking the wrong chemistry.
What removes it
A mild acidic treatment that dissolves the mineral bond, applied carefully and neutralised afterward. Concentration and dwell time have to be matched to the surface — strong enough to work, controlled enough not to etch the concrete or strip the stucco finish underneath.
Where it goes wrong
Undiluted muriatic acid is the classic mistake. It removes the deposit and etches the surface underneath, leaving a permanently lighter patch that is more obvious than the staining was. Acid on natural stone can destroy the finish outright — limestone, travertine and marble are especially vulnerable.
Preventing it recurring
Adjust sprinkler heads so they are not spraying the house or hardscape. It is the single most effective fix and it costs nothing. Where overspray is unavoidable, plan on periodic treatment as maintenance.
Key points
What the white streaks are
Local water carries dissolved calcium and magnesium. When it lands on a surface and evaporates, the water leaves and the minerals stay. Repeat that daily for a few years and you have a bonded crystalline deposit — chemically closer to soft rock than to dirt.
Preventing it recurring
Adjust sprinkler heads so they are not spraying the house or hardscape. It is the single most effective fix and it costs nothing. Where overspray is unavoidable, plan on periodic treatment as maintenance.