According to the American Water Works Association, the average daily U.S. total water use is 355 billion gallons. Besides domestic use, water is used for power generation and industrial, mining, aquaculture, livestock, and irrigation purposes.

The average daily U.S. domestic water use (indoor and outdoor) is 27.4 billion gallons or about 8 percent of total use. Of this water, 87 percent (23.8 BGD) is provided via public water suppliers. The remaining 13 percent (3.6 BGD) is self-supplied through wells and other infrastructure.

Estimates on per capita water consumption vary considerably. According to the U.S. Geological Survey’s 2010 Water Census, daily per capita water use in the United States is 88 gallons for domestic use. This includes both indoor and outdoor use. Desert Water Agency, Palm Springs, CA, finds per capita gallons per day is 135 for indoor and 72 for outdoor use. The U.S. Geology Survey finds per capita gallons per day are between 80 and 100 (indoor and outdoor).

According to WeCalc, a home environmental calculator designed by the Pacific Institute, my home uses 160 gallons of water per day — 59 gallons is outdoor use, which is 75 percent less than average.

My home water use is shown in Figure 1. WeCalc model also includes assumptions for home car washing. For example, the model suggests I would use 75 gallons of water with a bucket and 97 gallons with a hose with nozzle and 160 gallons with a hose and no nozzle.

Since I wash my car, on average, twice a month, my annual water consumption would be 2,328 gallons (2 X 12 X 97) according to the model.

So, if everyone with a registered light-duty vehicle washed their vehicle like me, total water use would equal 590.4 billion gallons (2,328 gallons X 253.6 million vehicles) or 1.6 BGD or daily per capita water use of 5.2 gallons (2012). 1.6 BGD is 6 percent of daily domestic use (1.6 / 27.4) and only 0.5 percent of total daily use (1.6 / 355).

By these measures, the total amount of water used to wash vehicles is virtually a drop in the bucket as compared to that of most other uses of water. Of course, not all vehicles are washed and not everyone washes the same way.

For example, one of my neighbors believes a car is simply a device to get from point A to B. Their cars are only washed and waxed twice a year at the dealership when they get an oil change whereas another neighbor takes his Cadillac every week to the local full-service car wash.

Consequently, it is difficult to quantitatively discern whether the benefits of water conservation in car washing outweigh costs. For example, if I visited a local conveyor wash for my needs, my cost would be $192 ($8 X 24) whereas my average annual cost to wash at home is about $25 for soap, water, towels, window cleaner, and laundry. If we assume DIFM provides no time value benefit as compared to DIY, using the commercial car wash would cost me an extra $167 annually.

According to one model, the commercial wash would save 1,608 gallons of water ((97 – 30) X 24) and 2,412 lbs of greenhouse gas emissions (1,608 X 1.5). At a cost of $3 per 1,000 gallons of water and $12 in social damage per metric ton of CO2, the environmental benefit would be $12.05.

If we applied this against 253.6 million vehicles, the upper limit of the environmental benefit of commercial car washing would be $3 billion savings in social damage and $12.68 million in water or 1.16 BGD (422 BGY / 365). As we noted earlier, estimated average daily U.S. domestic water use is 27.4 billion gallons.

Perhaps this is one reason why the professional car wash industry is wrongly and so frequently targeted when water shortages and droughts develop around the country. The amount of water may seem huge but it’s really pretty small in the grand scheme of things.

This is not to say there isn’t room for expansion of conservation measures in the car wash segments. According to trade journal surveys, roughly 60 percent of conveyor operators report they have wastewater reclaim systems, while 6 percent of self-service operators and 50 percent of in-bay automatic operators report having such systems.

If we applied these percentages against current estimates of 80,500 establishments, it would imply that about 38 percent of the car wash fleet reclaims wash water.

Of course, the car wash business and conservation aren’t always about dollars and cents. For example, I came across this water conservation question from a concerned customer:

“I am writing to find out if 5-Star Car Wash uses a water conservation system that saves water and diverts water from waterways into wastewater treatment. I’m assuming that you do, but I couldn’t find any information about it on your website.

This would be a great thing to promote on your website! You guys do a great job, and I’ve always been very satisfied with your service, and quality.

However, with the drought in full swing, I’d like assurances that you are operating in an environmentally friendly manner before bringing my car back in.

Thanks, Barbara B., Dixon, CA”

The reply comes from Bill Proestler, owner, 5-Star Car Wash, Vacaville, CA:

“Hello Barbara, Thank you for your inquiry.

Our two facilities are built to exceed the EPA and California requirements. We are part of the ICA WaterSavers program. Please refer to our website under the info tab and about us tab under affiliations. You will find a link to the International Car Wash Association.

Figure 3 – 5-Star Car Wash

We take our water consumption very seriously. All of our wastewater is collected in underground 7,500 gallon clarify tanks which separate the oil and sludge that come off vehicles.

The water is then discharged to the city treatment plant (sanitary sewer) without the oil and sludge. The city wastewater treatment plant further processes the water along with other sewerage before being released into the environment. About every six months we get our tanks pumped out for proper disposal.

Washing your car in the driveway uses more water and is hazardous to the environment. Because the chemicals (soaps) and oils from washing the car go down the storm drains and pollute the environment.

I appreciate you taking an interest in this. If you would like more information, I will be glad to arrange a tour of how it works.”

I’m not sure how Bill could sweeten this deal except to buy this customer a cup of coffee and mention that WaterSavers requires him to use 40 gallons or less of fresh water to wash a car.

Bob Roman is president of RJR Enterprises – Consulting Services ( You can reach Bob via e-mail at