They put EPDM roofs on commercial buildings and it lasts for decades. What building washes their roofs?
I read a post where one person said he does nothing to his roof, but will mow it if the grass gets too high.
I don't do anything to my roof and it is not discolored and I never have streaks down the sides.
The rain will wash the roof. Just check the caulking to prevent possible leaks.
Read this about EPDM roofs:
http://www.epdmroofs.org/what-is-epd...eral-questions