Choosing to wash a car in the driveway instead of using a car wash as a way to conserve water during a dry spell may not be the best choice, according to several studies and government entities.
The average driveway car wash uses a total of 116 gallons of water, according to the Massachusetts Department of Environmental Protection. Washing a car at home in the driveway or at a parking lot fundraiser will use between 40 and 140 gallons of water on a single car, according to the Western Car Wash Association.
“The amount of water used in our car wash process is significantly less than most people would expect. In fact, washing your car at Silverstar uses about half the amount of water than what is used when washing your car in your driveway,” said Andrea Vetos, regional manager for Silverstar.
Silverstar has at least 10 car washes in Sioux Falls and at least six in the Sioux City, Iowa, area.
The amount of water used depends on the driveway method, according to a 2013 study called “Water Saving in Domestic Car Washing” published online by ResearchGate. If buckets of water are thrown over a vehicle, the amount of water used could be more than 100 liters or 26.4 gallons. If a squeegee or sponge is used the amount could be 30 liters or 7.9 gallons. A power washer reduces the amount of water used.
The state of Massachusetts recommends using a car wash rather than a home wash because commercial car washes use about 60% less water and they are more environmentally friendly. The state’s department of environmental protection said most car washes recycle water. Also, water is sent through a sanitary sewer system where it’s treated. Unlike a driveway wash where water most often releases into a storm sewer.
The final stage of a wash at a car wash such as Silverstar involves debris removal.
“… non-recycled water is filtered out through our underground settlement tanks to remove debris and other sediment. This ensures that water leaving our property meets EPA standards,” Vetos said.
The use of recycled or reclaimed water in car washes has increased in part because it lowers demands on water and because it can be more economical. Also, California, for example, has a recycling requirement.
California has required newly permitted car washes to use recycled water for 60% of its wash and rinse since 2014.
Recycling/reclaim systems are also being used in South Dakota.
“We use a few different processes to limit water usage and recycle water when we can,” Vetos said. “Many of our locations utilize a water reclaim and treatment system, which uses an extensive filtering process to reuse water for future wash cycles.”
The equipment costs for a reclaim/recycle system was estimated at $15,000 with installation estimated at $20,000,according to a 2002 study by the International Car Wash Association(ICWA). The projected lifespan was about 10 years.
There are various types of reclaim/recycle systems with a range in costs.
In another state accustomed to periodic droughts, Arizona’s Department of Water Resources has advice for car wash owners.
The department recommends that car washes install a water recycling system for a 50% to 80% savings.
Vetos said Silverstar also reduces wasted water through its reverse osmosis process.
“… reject water is created when our equipment cycles. This reject water is stored in large holding tanks and used for some of our high-pressure rinse applications like our undercarriage flush,” Vetos said.
The ICWA released the results of a two year water use study in 2002. The study reviewed car washes in Boston, Massachusetts, Phoenix, Arizona, and Orlando, Florida.
The ICWA said the data could be used by car washes to conserve water and to prepare for drought conditions.
The study found that the use of reclaimed, or recycled water amounted to a high of 82% of the water used at one site to a low of 9% at another of the sites. Not all sites used recycled water.
The car wash service market is segmented into tunnels, roll-over/in-bay, and self-service, said Grand View Research.Roll-over/in-bay has grown and will continue to grow to 2025 for several reasons including low operating costs, less space required for installation, and low water consumption, according to the study which was released in 2020 and used data from 2015-2017.
In-bay/rollover services use 10-50 gallons of water per car while tunnel services use 14-60 gallons of water, according to Grand View.
The average amount of water used at a self-serve car wash is 17-18 gallons, according to the Western Car Wash Association.
Arizona’s water department says in-bay systems that roll a system around a vehicle are less efficient than an automatic conveyor. The average automatic conveyor system uses 44 gallons of water per vehicle. The average in-bay system uses 72.5 gallons of water per vehicle. New rollover and conveyor equipment can use less then 3.5 gallons per minute on light trucks and smaller vehicles, the water department said.
Systems can be improved through efficiency changes, reclaim systems and other upgrades, according to various industry analysis and studies.