I am a newbie to the Pressure Washing and Roof Washing Business from Ohio. Last year I purchased a trailered hot / cold HydoTek 3500psi 6 gpm 185 gal. unit. My questions are regarding roof washing shingled black streaked roofs. I have not tried this but there is a good market in my area for this service. I have read info and watched videos until I am now totally confused. Will I need to purchase a new low pressure pump setup or can I use my pressure washer with low pressure tips and a chemical injector. If I need to purchase a pump setup, what do you suggest I buy. Also any suggestions on the formula I should be using? Thank you so much for any help you can give me.