Cleaning with Pure Water

Cleaning with Pure Water

Cleaning with pure water is predominantly done by window cleaners in the domestic and commercial cleaning industry, it is also done in the critical and technical cleaning industry, but for now we will look at the use in window cleaning. The underlining principle of the use of purified water is the removal of hard water ions and suspended solids (dissolved halides are also removed) which would deposit on the windows as streaks after cleaning. This achieved by either filtration alone (using ion-exchange resin and activated charcoal) or filtration and reverse osmotic filtration in series. The combination of the two filtration systems produces highly purified water, that is then applied to the window and a brush is used to agitate it; further use of the pure water is then used to rinse, leaving no streaks behind.

Introduction To Cleaning

This process hasn’t changed in centuries and remains today as one of the most mature and well understood technologies known to man. What has changed over the years is the ingredients that make up the detergent; man-made ingredients have by in large replaced soaps in all but personal hygiene products. What all this means is that detergent products can be matched to a particular task or within a highly specific operating conditions, or a choice can be made when replacing one ingredient for another one because of a better environmental profile.

It is this last point, the environmental profile, that, because of the ever-tightening legislation, is being pushed to the forefront of cleaning and to the point where any detergent ingredient is deemed damaging to the environment; taken to this extreme is just plain hysteria. In recent years manufacturers have pretty much eliminated all the really environmentally hazardous ingredients in favor of much more benign ones, that’s not to say that this switchover is complete. So, the marketing of pure water cleaning systems by manufacturers seems to play into this hysteria; they aren’t wrong as such, more like they are adopting a rather simplistic approach.

The Marketing Hype

The common marketing statements state that pure water has a ‘natural tendency’ to be in its impure state or that pure acts a ‘magnet for dirt’. Pure water is just pure water, it prefers to be in any state, whether it’s pure or impure. What pure water is capable of is the initial and rapid dissolution of salts which tails off with time – this appears to make water seem enhanced. It is just a function of all solvents: water is a solvent and just one example. As a magnet for dirt, pure water is no better at cleaning greasy and oily soilings compared to tap water. Water, whether it’s pure or not will not mix with or dissolve oily soilings.

The most important factor in water’s cleaning ability is not purity, but temperature: the higher the temperature the greater the rate at which the salts will dissolve, and some salts won’t dissolve in cold water.


So, with all this we can say that using pure water as a window cleaning system is ok if the windows are regularly cleaned and free from greasy soilings. But if this system is to be adopted from an environmental point of view, you need to factor in the total energy costs of producing pure water, not just the absence of chemicals.

Dismissing all cleaning detergents as dangerous to the environment is being simply naive and just wrong. Detergents can be custom made to fit within the strictest environmental regime – the marine environment – and the latest detergent ingredients are safe enough to enter the aquatic environment in concentrated form.

Rafael Cobos