What is car wash Spot Free water?

When water evaporates from your vehicle as it is drying, it can leave 'spots' behind. These spots are formed from the dissolved solids in the water. Good quality spot free water has almost no dissolved solids in it. When spot free water evaporates there is no dissolved solids to be left behind to create 'spots'.

The method for applying spot free water is to try and push off all water from your vehicle starting at the top and working down. Spray out any crevices or places where water gathers, door and boot/hatch jambs for example, so that the only water left on your vehicle is spot free water.

The reason for spot free water drying without spots is that the amount of Total Dissolved Solids in the spot free water is close to zero ppm (parts per million).

1 ppm indicates 1 milligram of dissolved solids per 1 kilogram of water.

Water Source Total Dissolved Solids (TDS)
Spot free water < 5 ppm (ideally zero ppm)
Horsham tap water 78 ppm (as of August 2019)
Freshwater 500 ppm
Brackish water 500 - 30,000 ppm
Saline/sea water 30,000 - 40,000 ppm