Soft washing uses low pressure with a cleaning solution to gently wash siding and remove dirt, mold, and mildew from the surface. While low pressure is great for not damaging siding and other surfaces around your house the soft wash system uses a high amount of sodium hypochlorite (SH). The sodium hypochlorite found in the mix is what removes mold, mildew, algae, and other organic growths from the siding. Using to much of this chemical may damage your siding or other surfaces along with potentially killing plants, shrubs and trees.
A good question to ask before having your house pressure washed is, how much sodium hypochlorite (SH) is in your mix or what percent of SH will you be using when you wash my house?