We measure the water at the wash. A lot. Put simply, better water means a better wash, and it also means the wash equipment will stay better longer. So, every wash in town processes the city water to make better water with big industrial water softeners. They're just like the ones at your house, only about ten times bigger. But removing the hardness is still not enough to be considered "Spot Free". No matter how good the driers are, there will always be water evaporating off the car - especially in a hot Texas summer! When that water evaporates, anything that was in the water gets left behind as a gray film or spots. That's not hardness, but another measure called "TDS", or Total Dissolved Solids. The water coming out of your tap will have a TDS any where from 150 up to 600 in central Texas. For a car wash's spot free cycle, we want water with a TDS of less than 50. In fact, at Taylor Choice Wash, we keep our TDS below 10, usually around 6 or 7. We much prefer this approach to what other washes may do, which is to spray even more chemicals on the car (usually a silicone based spray) to keep the solids from sticking to your finish.