Car Washing

Why shouldn’t you wash your car at home?

The City of St. Paul is home to 10 lakes and is situated next to 13 miles of the Mississippi River. Every day, communities of plants and creatures are threatened by pollution entering these surface waters. Soapy grimy water from car washing that flows from your home into a storm drain will eventually end up in the Mississippi River.

Ideally, only clean rain water would enter storm drains. When cars are washed in streets, alleys, and parking lots, the dirty rinse water often goes into a storm drain. The dirty car wash water contains soap and detergent, and residues from exhaust fumes, gasoline, motor oil, heavy metals, and road grime washed off the car. In St. Paul, stormwater is not treated at the wastewater treatment plant, so by washing your car in your driveway or on the street, the dirty water rinsed off your car will likely make it to the Mississippi River.

What’s so bad about a little bit of dirty car water going down the storm drain? Soap, detergent, and grime contain chemicals that are harmful to fish and other aquatic life. Even “biodegradable” and “low phosphate” soaps contain harmful chemicals and should NOT go down storm drains. A little bit of soap and grime from a lot of people becomes LOTS of soap and pollution.

Plus, detergents in soap dissolve the grease and grim off cars, but when the detergents end up in creeks they dissolve the protective slippery mucous layer on fish and natural oils in the fish gills. Without the protective mucous layer, fish are more susceptible to bacterial diseases and parasites, and oxygen transfer in their gills is impaired. Just a tiny bit of detergent in the water can cause these problems for aquatic life. The “grime” that gets rinsed off the car contains heavy metals, hydrocarbons, and other chemicals that are harmful to aquatic life.

At commercial car washes, the dirty wastewater is sent to the wastewater treatment plant just like the water you use inside your home and business.