Good morning PWNers, Been washing away Katrina's sin down here in New Orleans and have come across a problem with brick homes. After pre-spraying the flood line ( white spoches where water sat ) with citrus cleaner then follow with turbo tip cleaning after drying white stains remain.Back with muric-acid pre spray then same cleaning technique with same results. Do I need to scrub after pre-spraying? or use different chemical.Some what new to business but catching on. Joe B. Mid- City Power Wash