Plus ∞.
If I understand correctly, @RiseNshine99, you’re only seeing the stubborn staining below the eaves? Some people call this phenomenon “fallout”, as it is from years and years of inorganic pollutants settling on the house and not getting rinsed off by the rain.
An acid like EacoChem’s OneRestore would probably do the trick. But I’ve seen some staining on vinyl siding that that stuff won’t even touch. Vinyl is non-porous to most substances, but apparently there are some things that can impregnate the vinyl and completely discolor it.
What I explain to my customers is that my softwash process removes organic contaminants on their siding in the safest way possible. The green, black, and brown growth on their siding should disappear entirely. But inorganic stains from poorly placed exhaust vents, damage from sun exposure (oxidation on gutters or siding), or build up from atmospheric pollution will most likely remain. I also cannot remove artillery “shotgun” fungus, safely.
It’s all about setting proper expectations. I try and live by the phrase, “under-promise, over-deliver”.
