The Environmental Impact of Washing Your Car

By: Deidra Metzler

There are various points of view regarding the environmental impact of washing your car as well as various methods to doing so.  That being said, some may question what impact, if any, car washing really has on the environment.  The first thing to be addressed is the bigger picture; wash water drainage.  Where does the wash water really go?  What impact does that wash water have on where it discharges?

All cities have different methods for directing water depending on its source.  For example, New York City, NY discharges ALL water to the sanitary sewer system where water is treated for various constituents (more information on sanitary sewer systems can be found here).  San Diego, CA on the other hand has two drainage systems, one is the sanitary sewer and the other is the storm drain system which discharges water, untreated, to nearby water bodies.  What distinguishes where the water is discharged to?  Location, location, location.  Water from your toilet, sink, bathtub, dishwasher, and washing machine discharges to the sanitary sewer; also known as black and grey water. This is the water that is treated.  The storm drain system drains to local water bodies; for San Diego, CA the water discharged to this system directly affects the Pacific Ocean.  Drainage points are found in streets, parking lots, and landscape in the form of curb inlets, catch basins, etc.

It is important to be familiar with this information to understand the direct impact different methods of car washing can have on the environment.  Knowing that water discharging to the storm drain system is untreated, it is important that car wash water is not discharged to it.  The majority of at home car washing results in discharge into the storm drain system because the wash water is not contained or collected.  Most commercial car washes prevent such discharges by containing wash water and directing it to the sanitary sewer.

What problems do wash water present to the storm drain system?  This also can depend on your location, and the types of pollutants your car may be exposed to.  However, it is most common for cars to have sediment and heavy metals on them.  The source of sediment accumulation is pretty obvious; however, heavy metals may not be an obvious pollutant.  Heavy metals such as copper can come from your brake pads.  Cadmium, lead, and zinc can be sourced from your tires and are considered pollutants to the storm drain system.  Sediment is problematic to aquatic life due to its ability to create a high turbidity, or cloudiness, in the water and the smothering affect it has on fish and amphibian eggs and gills.  Large quantities of heavy metals can be poisonous to all types of wildlife through ingestion or dermal absorption.

Another thing to consider is that infrequent washing of your car can also cause environmental detriment.  If you don’t wash sediment and other pollutants off your car on a regular basis any water discharge from your dirty car would most likely discharge to the storm drain system.  Water discharge from your car can include water from rain, sprinkler water hitting your car, etc.

Car washing can be performed at home without negatively affecting the environment if water is contained and/or redirected to prevent it from reaching the storm drain system.  To prevent water waste, it may be a good idea to collect wash water and distribute it to garden plants.  Or water can be collected and dumped in a drain leading to the sanitary sewer system.

Water can be collected through methods as simple as creating a barrier with sandbags.  Sandbags can be organized to direct water to a different location or to allow water to pool making collection easier.  Anther barrier option would be a large tarp or other similar fabric with a berm, which can be laid down to contain water from washing activities.  Other collection method examples are water vacuums or pumps, however these methods can be difficult without a pooled source of water.  Combining the sandbag or tarp and water pump methods can be extremely effective in reallocating wash water.  There are also products available that do not require the use of water to clean your car.  Such products would eliminate the need to contain wash water.

It is important to note that some commercial car washes are not always effective in containing all wash water.  Lack of complete containment can lead to a discharge to the storm drain system, which in many cases is considered an illegal discharge according to city regulations.  Illegal discharges can cause grounds for a citation and/or a fine by city officials.  Before utilizing a car wash ensure their wash water collection methods are effective in preventing discharges to the storm drain system.


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