Although this technique can remove some of the dirt and grime from your windows, the fact is… This technique can cause more damage to your glass than good.
Because your are allowing tap water to dry and remain on your glass. Remember, tap water contains hard minerals that, over time, will degrade the transparent look of your glass.
When using professional window cleaning techniques, tap water use is O.K. Mixed with soap, the harmful materials in tap water are completely removed from glass with squeegee and not left to dry into the glass surface.
If you are planning to use a garden hose to clean your windows, make sure to rinse the glass completely with pure water. You can effectively create pure water by running it through a reverse osmosis or DI-ionizing resin filtration system. RO and DI systems are available but expensive. These systems also require your household water pressure to fall within a specific range to allow the system to work properly.
The best solution is to hire a professional window cleaner in your area…
Especially if your window c leaning needs require the use of tall ladders or high-access equipment.