How to Get Green Stains Out of Concrete

Rinse the concrete with liquid soap and water to remove the algae, dirt and other particles. Scrub the stain in a circular motion using a brush. Rinse again to remove any soapy residue and blot it dry with a clean towel.

Set up the pressure washer according to the manufacturer's directions. You can rent a pressure washer at a large chain home improvement store, if you don't already have one.

Point the nozzle of the pressure washer about 6 inches away from the stained areas. Turn on the pressure washer and move the nozzle over the concrete until the green stain is no longer visible. Let the concrete air dry completely.

Apply algaecide to the concrete after it dries. This will prevent new algae growth. Read the directions before applying to the concrete. You can purchase algaecide at any home improvement store.