Cleans in less time and with less back breaking effort. Just spray and mop! No rinsing required. Non-abrasive formula dissolves and cleans heavy grime and chalk accumulation. Clean your roof at campgrounds or where water use is restricted. Biodegradable. Use on all types of EPDM rubber roofs. 1 quart cleans a 35' - 40' roof one time. Priced each.