How To Remove Black Stains From Concrete. Organic stains are carbon-based making them the toughest to remove. You may have to repeat the process if the stains have not been removed completely.
Allow the product. Use short brisk strokes for maximum penetration into the stain. Dispose of the contaminated water safely.
Forget with 5 parts water in a pump-up garden sprayer.
How to clean a stained concrete patio - YouTube. 12122019 If its water thats causing black stains on your concrete you can get rid of the dark spots using an acid rinse or a power washer. Apply an organic detergent as recommended above to damp concrete. Use a mild-abrasive brush to scrub the affected area until all the visible black mold.