I have been working my way into Roof Washing business and have done about 30 roofs. My problem is I am always so nervous about damaging flowers and grass, etc. I am using in a 60 gallon tank, 60 percent 12.5 Bleach, 35 percent water and two bottles of 91% alcohol and some laundry soap. ANY HElP out there for Me. I would really appreciate GOOD Solid advice. ThaT is VERY effective for folks.