Normal tap water is purified, using reverse osmosis and de-ionisation resin, which, without getting too technical removes all contaminants and dissolved substances to leave a pure or neutral water. The neutral water acts like a sponge and all the dirt and residues (which will be positively or negatively charged) are then attracted to this water. Therefore, when a window is washed with pure water, the residues that are found on the glass are absorbed by the water and rinsed off. The pure water is pumped from a large water tank in our company van, through a hose and up a telescopic carbon pole with a brush on the end making almost all windows safely accessible.