Dear EarthTalk: What is the most environmentally friendly way I can wash my car: doing it myself or going to the local car wash? -- Jim, Denton, TX

Few people realize that washing our cars in our driveways is one of the most environmentally un-friendly chores we can do around the house. Unlike household waste water that enters sewers or septic systems and undergoes treatment before it is discharged into the environment, what runs off from your car goes right into storm drains -- and eventually into rivers, streams, creeks and wetlands where it poisons aquatic life and wreaks other ecosystem havoc. After all, that water is loaded with a witchs brew of gasoline, oil and residues from exhaust fumes -- as well as the harsh detergents being used for the washing itself.

On the other hand, federal laws in both the U.S. and Canada require commercial carwash facilities to drain their wastewater into sewer systems, so it gets treated before it is discharged back into the great outdoors. And commercial car washes use computer controlled systems and high-pressure nozzles and pumps that minimize water usage. Many also recycle and re-use the rinse water.

The International Carwash Association, an industry group representing commercial car wash companies, reports that automatic car washes use less than half the water of even the most careful home car washer. According to one report, washing a car at home typically uses between 80 and 140 gallons of water, while a commercial car wash averages less than 45 gallons per car.

If you must wash your car at home, choose a biodegradable soap specifically formulated for automotive parts, such as Simple Greens Car Wash or Gliptones Wash n Glow. Or you can make your own biodegradable car wash by mixing one cup of liquid dishwashing detergent and 3/4 cup of powdered laundry detergent (each should be chlorine- and phosphate-free and non-petroleum-based) with three gallons of water. This concentrate can then be used sparingly with water over exterior car surfaces.

Even when using green-friendly cleaners, it is better to avoid the driveway and instead wash your car on your lawn or over dirt so that the toxic waste water can be absorbed and neutralized in soil instead of flowing directly into storm drains or open water bodies. Also, try to sop up or disperse those sudsy puddles that remain after youre done. They contain toxic residues and can tempt thirsty animals.

One way to avoid such problems altogether is to wash your car using any number of waterless formulas available, which are especially handy for spot cleaning and are applied via spray bottle and then wiped off with a cloth. Freedom Waterless Car Wash is a leading product in this growing field.

One last caution: Kids and parents planning a fundraising car wash event should know that they might be violating clean water laws if run-off is not contained and disposed of properly. Washingtons Puget Sound Carwash Association, for one, allows fund-raisers to sell tickets redeemable at local car washes, enabling the organizations to still make money while keeping dry and keeping local waterways clean.

CONTACTS: International Carwash Association, Simple Green, Freedom Waterless Car Wash, Puget Sound Carwash Association

CarJunky Recommends Simple Green for your car cleaning needs.