“How are you getting on with the new window cleaners, mom?” “Well, they don’t do a proper job…they don’t dry the windows after they’ve been cleaned!” Customers (like my mom) who are new to modern window cleaning methods often have this common misconception. So, the question is, why don’t window cleaners dry windows anymore? Let’s take a closer look.
The adoption of the water-fed pole system has revolutionised the window cleaning industry. This modern window cleaning method has led to a noticeable change: many professional window cleaners no longer dry windows after cleaning. By eliminating the need to climb ladders and dry each window manually, window cleaners can complete jobs more efficiently with increased safety.
The water fed-pole method of cleaning windows contrasts with traditional techniques that require the use of a squeegee (a T-shaped rubber-edged tool) to blade the water away from the glass and a drying cloth to buff away any streaks. This is why some customers may initially be concerned about not having their window windows dried manually, fearing potential streaks or spots.
It’s logical to think that water droplets left on windows to air dry would leave marks when they evaporate. This is indeed the case with tap water due to its high mineral content. Minerals remain on the glass after tap water has evaporated leaving unsightly water stains. You only need to take a look inside your kettle, around your taps or on your shower screen to see evidence of the residue left by hard water. So how do window cleaners overcome this obstacle to achieving crystal clear windows?
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Why purified water is the modern window cleaner’s secret weapon
Modern window cleaning methods involve the use of a pure water-fed pole system. With this technique, the water flows through a hose and exits via a telescopic pole with a brush attached at its end. For this system to work effectively, window cleaners must use water that has been filtered using a purification system to remove dissolved mineral solids. Since ‘pure’ or ‘deionised’ water is free of minerals, it dries to leave a sparkling clean finish. Using purified water means that window cleaners don’t need to blade the water away from windows using a squeegee; it can be left to air dry.
In the UK, water hardness is measured in parts per million (ppm). According to the Drinking Water Inspectorate (DWI), water hardness is caused by dissolved calcium and magnesium. Depending on local geology, the hardness of the water supply will vary. Soft water (predominantly in Scotland, Wales and the North of England as shown in water hardness map) has a ppm of up to 100 with very hard water having a ppm of 300 or more. To give this context, rainwater has a ppm of between 10-20 on average. It’s clear to see (pun intended!) that tap water contains far too many mineral deposits to be used in a water-fed pole system (this is also why I never use unfiltered tap water on my houseplants!).
How important is the right cleaning technique?
Does this mean that window cleaners can simply spray pure water on your windows and go? Not exactly. The right cleaning technique is required. Purified water attracts dirt and mineral deposits, which is why windows need to be scrubbed using the brush end of the water-fed pole to agitate the dirt and then rinsed thoroughly to remove the loosened grime. Windows should also be cleaned from top to bottom so that the dirt water solution is completely removed, and only pure water is left to dry on the windows. Finding a window cleaning company that is experienced in using the pure water-fed pole system and who trains its staff in efficient modern techniques is an essential way of ensuring that your windows are left sparkling clean. Inexperienced or untrained window cleaners just won’t cut the mustard with modern window cleaning systems.
It is important to note that the pure water-fed pole system is exclusively designed for external window cleaning. For internal windows, window cleaners must continue to rely on traditional methods.
Why the right level of water purity counts
What if your window cleaner does all of the above and the water droplets are still leaving a residue once dry? The issue would likely be that the water supply that they are using to clean the windows is not sufficiently pure. The key is to use water that has been purified to a mineral content of 0 parts per million (ppm). To check whether the water has been purified to this degree, window cleaners use a Total Dissolved Solids (TDS) meter. Here comes the science bit: a TDS meter measures the amount of dissolved solids in the water by measuring its electrical conductivity, which increases when dissolved solids like salts and minerals are present.
So how do window cleaners achieve a water purity level of 0ppm? There are a variety of pure water filtration systems on the market. It is important that a combination of two purification systems are used to fully remove the mineral content of tap water. The two systems used are Reverse Osmosis (RO) and Deionizing (DI). The process of Reverse Osmosis forces water at high pressure through a semi-permeable membrane. Reverse Osmosis is effective at removing most of the mineral content; some manufacturers state that their RO systems remove 90%-95% of dissolved minerals and salts from the water and others claim to remove up to 99%. The level of water purity achieved with RO systems ultimately depends on the quality and proper maintenance of its semi-permeable membrane along with a sufficiently pressurised water supply.
However, to make the water completely pure (0ppm) so that it can be used by window cleaners in the water-fed pole systems, a Deionising Vessel is also recommended. A Deionising (DI) Vessel is a pressurised canister that channels water through a resin filter. The resin in the vessel attracts non-water ions and replaces them with water ions. The DI system is effective at purifying the water to 0ppm (provided that the resin is replaced regularly).
Window cleaners in soft water areas such as Wales might be able to get away with just using a DI system, which can at the end of the day reduce any level of water hardness down to 100% purity (0 ppm); this is not the case in hard water areas. It is very energy consuming and costly to bring hard water down to total purity with a DI system alone. That is why a combined Reverse Osmosis and Deionising system is the most practical and environmentally friendly filtration option.
Why quality control measures are necessary
Once again, these two purification systems (Reverse Osmosis and Deionising) are only as good as their filters. A window cleaning company should be regularly monitoring the purity of their water supply with a TDS (Total Dissolved Solids) meter and replacing the RO and DI system filters when a reading of anything over 0ppm. Regular quality control monitoring is the only way to maintain a water supply that is consistently pure enough to leave a clear finish.
The word on the street is that some window cleaners will still clean windows with a ppm of10-20. However, as we've seen, achieving water purity of 0 parts per million (ppm) is essential to ensuring that no residue is left on the windows.
Conclusion
The transition away from manual drying in professional window cleaning is largely due to the adoption of the pure water-fed pole system. This method leverages purified water to clean windows effectively, allowing them to dry naturally without leaving streaks or spots. The benefits of enhanced safety, increased efficiency, and environmental considerations make this approach the preferred choice in the modern window cleaning industry.
At Midway Cleaning Services Ltd, we believe that only completely pure water should be used to guarantee our customers the best possible cleaning result. Our window cleaners are fully trained in modern window cleaning techniques to give you the sparkling clean windows that you deserve. Contact us for a no obligation quotation.
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