I have tree sap what dribbles from the maples next to my asphalt driveway every spring. Then pollen season kicks in with bee poo, leaf season with tree caterpillars dropping digested leaves, and berry season with purple bird poo. By late summer, it's blotchy ugly with lichen and moss gaining a toehold. I do an 80 foot by 5 foot strip with a 2 gallon sprayer with no excess runoff. 3 passes, let it work, rinse, move the car, 3 more passes, rinse, and it's done. The brick steps and concrete walkway get the same treatment. I had a cheap pressure washer but it lasted one season - not designed for extended use, apparently. Bleach takes less time and doesn't erode the surface.
If you live in a place with sinners rampant, you'll get 40 days and 40 nights of deluge from the heavens every year. Maybe more.