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washing your car at home vs. using a carwash

I usually don’t wash my car in the winter. I’d like to say this is because I’m trying to save water and help the environment, but mostly it’s because it usually snows or rains 10 seconds after I wash it, which totally defeats the purpose of washing it in the first place. However, with summer coming up I have no such excuse. But because I do care about the environment, I want to make sure I’m using as little water and causing as little pollution as possible. So here’s my question: is a car wash or washing at home better for the environment?

By the numbers

Let’s take a look at the numbers for washing your car at home:

  Wash at home
Flow rate (average garden hose) 8 GPM
Rinse 1 4 min. x 8 GPM = 32 gallons
Soap 5 gallon bucket of soap and water
Rinse 2 5 min. x 8 GPM = 40 gallons
Total 77 gallons [1]

And here are the numbers for an automatic car wash:

  Automatic wash [2]
Flow rate 3 GPM
Pre-soak 5.3 min. x 0.6 GPM = 3.2
Wash and rinse 2.6 min. x 3 GPM = 7.8
Total 11 gallons [3]

I was really surprised by the numbers. I was so sure that washing your car at home would use less water. But there are other factors to consider as well.

Water pollution

Water pollution is another concern when washing your car. But if you think about it, it’s pretty much common sense. When you wash your car at home, the soap (and the gross stuff it cleans off, like oil, grease, tar from roads, etc.) will mostly likely run down your driveway and into a storm drain intended only for rain water.

This pollution can end up in groundwater, lakes, rivers, and streams and hurt the wildlife found therein. Sadly, when detergents and soaps get into streams, they destroy the layer of mucus on fish scales that protects fish from bacteria and pesticides.

Automatic car washes are required by law to dispose of their waste water cleanly by pumping it to a waste water or chemical treatment plant.

Water conservation

In the end, getting your car washed commercially is the better option for the environment. But whatever you decide to do, here are some tips to help conserve water and limit pollution.

At a carwash

  • Ideally, choose a car wash that recycles water
  • Choose a car wash that properly disposes of waste water
  • Wash your car less often

At home

  • Wash your car on the grass so the waste water soaks into the ground
  • Use a hose that stops the flow of water when you release the trigger
  • Wring your rags or sponges into a bucket, then empty those buckets into a sink or toilet
  • Choose biodegradable soap or cleaner
  • If possible, collect rainwater and use that to wash your car

What do you do to conserve water when you’re washing your car? For other ways to use less water, check out this post on native landscaping.

Photo by Or Hiltch


[1] This is a super conservative estimate. The EPA claims that the average person washing a car will use more than 500 gallons.

[2] These numbers came from this great article about using a home car wash vs. an automatic car wash.

[3] This estimate may be low as well. I ran across many different numbers, including 45 gallons and 75 liters, which is about 20 gallons.

 

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