Generally, there are three types of water used in car washes: hard water, soft water, and reverse osmosis water. It is important to know when to utilize each type of water in a car wash because each has an impact on producing a clean and dry car. Hard water creates problems when used with detergents and presoaks by reacting with some of the components in those products. However waxes and drying agents work best with hard water.
Soft water produces the highest foam levels and most consistent cleaning performance. Soft water is created in a water softener by replacing hard ions with sodium ions. Unlike hard water with hard ions, sodium ions do not have any negative effect on detergents and presoaks, making it the best choice for the wash component of a car wash.