I own a large 4 wheel drive and my wife owns a relatively small sports car. I washed the 4 wheel drive with a hose and calculated my water usage as between 18 and 20 litres of water. I washed my wife’s car with buckets and no hose and used 5 buckets of water. Details of the calculations are shown below.
When I looked on the internet I found lots of claims that washing used about 180 litres of water. The earliest of these I found was an article in the Melbourne Age at http://www.theage.com.au/news/national/ ... 42426.html which quoted the Australian Car Wash Association as its source. This article quoted the usage when washing with buckets at 180 litres (20 buckets full), when using a hose it was 130 litres.
Another interesting site at http://eco-carwash.co.za/ quoted from 360 to 630 litres of water used per car but gave no reference as to the source of these numbers (This seems to be a South African site advertising waterless car wash products so their litres may be different to ours).
The calculations below are based upon the water flow at my house which is better than most places I have lived in. It takes about 45 seconds to fill a 9 litre bucket through a hose with a fairly standard nozzle. This equates to 11/3 litres per minute.
Hose wash of 4 wheel drive
2 minutes to wet the car down thoroughly 2.67 litres
I bucket of water with detergent 9.00 litres
1 Minutes to rinse roof & bonnet 1.33 litres
4 minutes to rinse sides & back 5.33 litres
Total 18.33 litres
Bucket was of sports car
1 bucket to wet car down with a sponge 9 litres
I bucket of water with detergent 9 litres
1 bucket to rinse roof & bonnet 9 litres
2 buckets to rinse sides & back 18 litres
Total 45 litres
As a footnote I talked to Tonys Mobile Car Detailing who normally wash my car and they told me that they use 100 litre water tanks and expect to clean 5 cars without having to refill their tanks, an average of 20 litres per car.
