EPA's Region 6 Office
Serving: Arkansas, Louisiana, New Mexico, Oklahoma, Texas, and 66 Tribal Nations
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Section 301 of the Clean Water Act (CWA) prohibits a point source discharge of pollutants into waters of the United States without an NPDES permit. To legally discharge wash water, a pressure wash operator must obtain an NPDES permit for each discharge location. Due to the fact that many pressure washer operators are mobile, it is not realistic to pre-determine discharge locations and obtain permits for each location. Additionally, most NPDES permitted process water discharges require treatment and analysis of the discharge, which may not be practical for many pressure washers.
The most common method of compliance with the CWA is to prevent process wastewater discharges to waters of the United States. If your discharge does not reach waters of the United States, then there are no requirements under the CWA. Examples of compliance without a discharge are vacuuming up the process wastewater or berming the process water and allowing it to evaporate. An additional method of compliance is to discharge the water to an NPDES permitted sanitary sewer system (the municipality may have additional pretreatment requirements before accepting your discharge). The most common form of non-compliance is to discharge the process water into a storm sewer system or into a city street that drains to a storm water inlet. Most storm drainage systems in Region 6 discharge directly to waters of the United States without treatment, which means anything that discharges into a storm drain is the same as putting it directly into the waterbody receiving the storm drain discharge.
Washing vehicles is an example of a process water discharge of pollutants requiring an NPDES permit if it reaches waters of the United States. EPA recommends that companies or individuals take their vehicles to car washes*. If a car wash is not available, NPDES permit requirements may be avoided and impacts on waters of the United States minimized if vehicles are washed in a vegetated or grassy area where the wash water will be absorbed into the ground instead of allowing it to run into the street and then into a storm drain. There may be additional requirements if chemicals (detergents, waxes, etc.) are improperly used or if the absorbed water will reach an underground water body.
*A properly operated car wash discharges all of its wash water to a municipal sanitary sewer system that treats the wastewater before discharging from the wastewater treatment plant to waters of the U.S. Most municipalities have a pretreatment program requiring car washes to perform some type of pretreatment such as discharging through a sand filter and grease trap.