Steve, When spraying concentrated chemicals that are highly corrosive, which I suspect your roof cleaner is, you want no metal (except ss) in the system. Use nylon fittings, rubber hose, pvc wands, nylon nozzles and pvc ball valves.
For roofs, I use a straight wand with two elboes and a nozzle at the end. This is used to walk and sweep back and forth. For large areas, I built out of pvc a two wheel cart (plastic wheels & ss axle) with handle and a ball valve. Over the wheels is an aluminum bar with three nylon spray nozzles that covers 54" at a pass. The angle and size of the nozzles is critical and is sized to your pump. I use this on roofs that are walkable. E-Mail me if you want more specs on the wand and cart. When using the wand I get $100.00 / hour, and when using the cart, I get an unbelieveable $400.00 / hour. Not bad for a $40.00 cart.
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Baldwin Power Wash, Inc. serving the Gulf Coast between Mobile, AL and Pensacola, FL.