The Roof Cleaning Institute Of America Training & Certification Forum
"Find A Certified Roof Cleaner Directory"

Check one of these http://legacy.shurflo.com/pages/new_industrial/Industrial/automotive/doc_sum/94-260-21.html

I am 90% a Pure Roof Cleaner these days (I send exterior cleaning  work out to pressure washers who send us roofs to clean).
But, I have "softwashed" thousands of homes, in my day. 
I always wanted to TRY one of these little bastards.
Heck, with one of these, you might be able to just keep a shingle roof mix in your tank, then turn on a valve to feed one of these little guys, and "softwash" away!
These little guys automatically dilute whatever is IN your tank by a 1/3 rd.
So, this means, if you had pure chlorine in your tank, this little guy will shoot out a stream of 2/3 water, and 1/3 chlorine (33%) !
It has a smaller brother, that will dilute the mix by 1 part chlorine to 5 parts water.
It is powered Purely by water, that means no 12 volt motors to fail.

LOL, Just a Thought :)