Drinking water is an increasingly scarce asset, and it should be made every effort to preserve water reserves still available. More than preserve an indispensable resource for future generations, saving water means economic savings for current generations (reducing potable water consumption and costs of waste water rejection).
For washing vehicles it is still used a great quantity of drinking water, and usually the quality of this water is much higher than the necessary for this purpose. The big problem is that in most cases we use drinking water for these purposes only for the reason that it is the only source available.