Car Washing

Adapted from USEPA Stormwater Best Management Practices Fact Sheet


Image of car washing This management measure involves educating the general public, businesses, and municipal fleets (public works, school buses, fire, police, and parks) on the water quality impacts of the outdoor washing of automobiles and how to avoid allowing polluted runoff to enter the storm drain system.

Outdoor car washing has the potential to result in high loads of nutrients, metals, and hydrocarbons during dry weather conditions in many water- sheds, as the detergent-rich water used to wash the grime off our cars flows down the street and into the storm drain. Commercial car wash facilities often recycle their water or are required to treat their wash water discharge prior to release to the sanitary sewer system. As a result, most storm water impacts from car washing are from residents, businesses, and charity car wash fundraisers that discharge polluted wash water to the storm drain system. According to the surveys, 55 to 70 percent of households wash their own cars, with the remainder going to a commercial car wash. Sixty percent of residents could be classified as "chronic car-washers" who wash their cars at least once a month (Smith, 1996, and Hardwick, 1997). Between 70 and 90 percent of residents reported that their car wash water drained directly to the street and, presumably, to the nearest stream.


Car washing is a common routine for residents and a popular way for organizations such as scout troops, schools, and sports teams to raise funds. This activity is not limited by geographic region, but its impact on water quality is greatest in more urbanized areas with higher concentrations of automobiles. Currently, only a few pollution prevention programs incorporate proper car washing practices as part of an overall message to residents on ways to reduce nonpoint source pollution. Other programs have extended this message to include charity car washes and provide these charity groups with equipment and training to alleviate the problems associated with polluted wash water entering the storm drain system.


The development of a prevention program to reduce the impact of car wash runoff includes outreach on management practices to reduce discharges to storm drains. Some of these management practices include the following:
  • Using a commercial car wash.
  • Washing cars on gravel, grass, or other permeable surfaces.
  • Blocking off the storm drain during charity carwash events or using an insert to catch wash water.
  • Pumping soapy water from car washes into a sanitary sewer drain.
  • If pumping into a drain is not feasible, pumping car wash water onto grass or landscaping to provide filtration.
  • Using hoses with nozzles that automatically turn off when left unattended.
  • Using only biodegradable soaps.
  • Minimize the amounts of soap and water used. Wash cars less frequently.
  • For businesses, good housekeeping practices can minimize the risk of contamination from wash water discharges. The following are general best management practices that businesses with their own vehicle washing facilities can incorporate to control water quality impacts from wash water discharges:
  • All vehicle washing should be done in areas designed to collect and hold the wash and rinse water or effluent generated. Wash water effluent should be recycled, collected, or treated prior to discharge to the sanitary sewer system.
  • Pressure cleaning and steam cleaning should be done off-site to avoid gener- ating runoff with high pollutant concentrations. If done on-site, no pressure cleaning and steam cleaning should be done in areas designated as wellhead protection areas for public water supply.
  • On-site storm drain locations should be mapped to avoid discharges to the storm drain system.
  • Spills should be immediately contained and treated.


The effectiveness of car washing management practices at reducing nonpoint source pollutant loads has yet to be measured accurately. Due to the diffuse nature of nonpoint source pollution, it is often difficult to determine the exact impact of a particular pollution prevention measure at reducing pollutant loading. While not much is known about the water quality of car wash water, it is clear that car washing is a common watershed behavior.

Residents are typically not aware of the water quality consequences of car washing and do not understand the chemical content of the soaps and detergents they use. Car washing is a very difficult watershed behavior to change since it is often hard to define a better alternative. However, as with all pollution prevention measures, the reduction of pollutant loads from outdoor car washing activities are bound to have a positive effect on storm water quality.

Cost Considerations

Staffing and materials represent the largest expenditure for local governments seeking to administer a nonpoint source education program. Car wash outreach programs are relatively inexpensive to staff and often require only a limited outlay for materials (brochures, training videos, etc.), and staff time devoted specifically to car wash education can be less than 5 percent of an employee’s time. For Kitsap County, Washington, the Sound Car Wash program requires roughly 10 to 15 hours a week of staff time over a 25-week period from April to September. Cost for materials and equipment replacement is estimated to be between $1,500 and $3,000 for the same 25-week period (Kitsap County, 1999). The Clean Bay Car Wash kits program in Tacoma, Washington, uses only the catch basin insert option and estimates that it spends no more than $2,000 per year and less than 2 weeks of staff time per year to handle requests for its program.

The purchase of wash water containment equipment is often a one-time expense, and this equipment is often used for a number of years. Two pieces of equipment used in car wash programs developed in the Pacific Northwest provide an example of the potential equipment cost. For the catch-basin insert, the approximate cost of installation is $65. In some cases, locations where charity car washes are frequently held have constructed their own catch basin inserts using plywood. For the Bubble Buster, the cost ranges from $2,000 to $2,500.


Center for Watershed Protec tion. 1999. On Watershed Behavior. Watershed Protec tion Techniques
3(3): 671-679.
Natural Resources Defense Council. 1999. Stormwater Strategies: Community Responses to Runoff Pollution. Natural Resources Defense Council, Inc, New York, NY
USEPA Pollution Prevention/Good Housekeeping for Municipal Operations USEPA. Vehicle Washing Fact Sheet.
Smith, J. 1996. Public Survey Used to Estimate Pollutant Loads in Maryland. Technical note 73. Watershed
Protection Techniques. 2(2): 361-363.
Hardwick, N. 1997. Lake Sammamish Watershed Water Quality Survey. King County Water and Land Resources
Division. Seattle, WA. 122p.