Do you have a concrete sidewalk or walkway that is turning brown or green in color? Maybe you've noticed that the concrete has some spots or stains on it. In any of these cases, you should take steps to clean the sidewalk before the stains become more permanent, and before the algae causing many of them becomes slippery and hazardous. The best way to clean more concrete sidewalks is with a power washer. Whether you buy one or rent one, follow these steps for great results.
Start by pre-soaking with a concrete washing solution.
Most home improvement and hardware stores, and even some landscaping supply stores, sell cleaning solutions made for use with power washing systems. You'll see some all-purpose cleaners, and if this is all your store has, it can work. However, if you see a cleaner made for concrete, that is the one you want to buy. Cleaners made specifically for concrete tend to be stronger and more effective. The manufacturers can make them this way since they don't have to worry about buyers using them on more delicate materials like vinyl siding.
With your cleaner in hand, fill the soap compartment in your power washer. Then, put the soaker or low-pressure nozzle on the washer. Spray down a section of the concrete sidewalk. Use plenty of water; the goal is to get the area completely wet. Then, wait for about 10 minutes. The cleaner will loosen the grime — especially that black algae, which can be really sticky.
Spray with high pressure.
After the soap has had some time to sit, you can start actually pressure washing the sidewalk. For this, you need to use the high-pressure tip. For some models, this is the 2,000 PSI tip. For others, it may be the 2,400 or 2,800 PSI tip. These nozzles are set at an angle so that you can hold the pressure washer wand straight and get a better effect. You'll want to hold the pressure washer tip about 6 inches from the sidewalk and move it back and forth over a small area to fully remove the algae and grime.
When you reach the edge of the area that you pre-soaked, put the lower-pressure nozzle back on your power washer. Rinse the area that you just cleaned to remove the surface debris.
Then, repeat these steps with another portion of the sidewalk. Soak it with soap, let it sit, wash it on high pressure, and then rinse it again on low pressure. Before long, your whole sidewalk will be clean and pristine.