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When choosing a pressure washer to clean concrete, choose a machine with a pounds-per-square-inch capability of 2,200 to 3,500. Use a 0- or 15-degree nozzle for pressure washing concrete. The 0-degree nozzle is used for blasting away soil. It has a very tight pattern, so if not used properly, it can leave trail marks on the concrete. The 15-degree nozzle has a fine jet that is larger than the 0-degree nozzle. It does not have the blasting power of the 0-degree nozzle, but the slightly wider spray pattern is less likely to leave streaks on the concrete. Always work from one edge of the concrete to the opposite edge to be sure all of the concrete is cleaned evenly.
Oils, solvents, paint and other regulated environmental contaminants that have been spilled on the concrete may be enter the environment while cleaning. In addition, some chemicals used to clean concrete are an environmental hazard. The Environmental Protection Agency has strict guidelines requiring containment of these environmental hazards to prevent them from entering groundwater and storm drains. If containment is required by local ordinances, there are large sponges that can be placed at the lower end of the cleaning project that will filter out dirt and oil yet allow the filtered water to discharge freely. These sponges reduce the amount of waste, so the disposal costs less. Check with your local municipality or Environmental Protection Office for local regulations and proper disposal methods. Fines relating to illegal disposal of waste may be a lot higher than containment and proper disposal. -
Liquid dish soap is often strong enough to clean grease and other stains from concrete. A solution of liquid dish soap and hot water can be poured directly on grease stains, allowed to soak and cleaned off with a pressure washer using hot water. Dishwasher detergent can be used for difficult grease and oil stains. Mix dishwasher detergent with hot water and pour on the stain. Then pressure wash using hot water to rinse the solution from the area.
Paint and other coatings can often be removed with a solution of baking soda and hot water. Mix 1 lb. of baking soda to 3 gallons of water and use this solution to fill the cleaning product reservoir on the pressure washer. Pressure wash using hot water to help soften the paint or coating for removal. - Annual cleaning reduces the amount of chemicals needed and the cost of disposal of waste. Always clean up spills on concrete as soon as possible to reduce the need for pressure washing more frequently. Consider a washable coating so spills that can be cleaned up easily and future pressure washing will not be required.
