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Pure Water Window Cleaning

The Value of Pure Water


Not too long ago, a visit to a window cleaning trade show would reveal only a handful of manufacturers and distributors displaying water fed poles and water purification systems used for spot free window cleaning without a squeegee. Today, there’s hardly a booth on the floor not embracing the technology, which allows end users to stand safely on firm ground cleaning glass at multi-story heights.  The phenomenon was born in the United Kingdom where cleaning windows on ladders has been banned in recent years because of so many deaths and injuries due to falls.  It spawned the European Union’s Work At Height Regulations.  With “At Height” defined by the Union as any height from which a person could be injured falling from it – even a small step ladder – it’s little wonder that the use of water fed poles and water purification systems has seen explosive growth there.  While not so in the U.S. where no such regulations have been forthcoming, smart window cleaners are nonetheless on to it, not only for the safety factor but for time savings on the job and the short learning curve involved in training.

Getting to know it

Hearing about how water purification systems work, let alone learning how to use them, can be boring.  Like teenagers, most people don’t want to know how things work; they just want whatever it is to perform without having to read the instructions.  However, window cleaners should have an understanding about the science of water.  For those wanting to come up to speed on the matter following is a succinct and, hopefully easily understood narrative on the water purification processes covered in this article.

About Reverse Osmosis

The following explanation of Reverse Osmosis (RO) is based on research, consultations, and a seminar presented at the February 14, 2008 IWCA convention by Henry Avina, engineering general manager at R.O. Ultratec USA, INC..  The Fallbrook California, company manufactures water purification components including reverse osmosis membranes for RO systems manufacturers.
To understand RO, you need to understand osmosis, which in physiology terms is a process by which water and nutrients are supplied to living cells.  The wall of a living cell is a natural membrane called a semi permeable membrane meaning that the membrane is selective – some substances can pass through it while others cannot.
The process of osmosis works like this: Imagine a container of water split down the middle with one side having a higher concentration of Total Dissolved Solids (TDS) than the other side.  Further imagine that the two sides are separated by a semi permeable membrane that allows water from the lower concentration of substances to pass though to the higher concentration side.  This results in the liquid level on the higher side being forced to rise.  By exerting pressure on the high concentration side, you can actually reverse the flow of water through the membrane, from the high concentration side to the side of lower concentration.  That is Reverse Osmosis (RO).
TDS are the total amount of mobile charged ions, including minerals, salts or metals dissolved in a given volume of water, expressed in units of mg (milligrams) per unit volume of water (mg/L), also referred to as parts per million (PPM). TDS is directly related to the purity of water and the quality of water purification systems and affects everything that consumes, lives in, or uses water, whether organic or inorganic, whether for better or for worse.
Some materials that may be dissolved in water include calcium, magnesium, sodium and iron. If a material will completely dissolve in water and is not visible in the water it is part of the TDS.  While it’s known that substances are in the water contaminating it, they are invisible to the naked eye. The RO process helps lower TDS content because substances such as calcium, magnesium, sodium and iron cannot readily pass through the membrane – water can. RO can reduce the total dissolved solids content in water by 85-to-99%.

How RO Systems Work

Water entering an RO system is called feed water.  When it reaches the membrane, some of the water – minus most of the dissolved solids – passes through the membrane,  The water that passes through the membrane is called the permeate,  The permeate is the product water used in window cleaning via water fed poles.  The waste product or reject water – the water with dissolved materials that will not pass through the membrane passes out and down the drain.  That product is also called the concentrate.  What happens is that most, though not all of the ions originally present in the feed water – the water supply for the system – are rejected in the RO process.  That is, they cannot pass through the semi permeable membrane but instead, flow out as the waste product.
Typically, for every gallon of water produced, a gallon of waste water is generated as well, according to Henry Avina.  However, the ratio of product water to waste water depends on the design of the system you use.  For example, systems with multiple membranes result in more product water and less waste water.  He pointed out that another method to increase the ratio is incorporated in some systems that take a portion of the waste water and feed it back through the system again.


Deionization (DI) is another process for producing pure water.  Recall from physic class that an ion is an electrically charged atom or group of atoms formed by the loss or gain of one or more eclectrons.  Deionization process uses specially-manufactured ion exchange resins which attract and remove the dissolved solids from water, producing a high purity water that’s generally similar to distilled water.  Deionization removes 99% or more of the dissolved solids, producing very high quality water.  While deionization removes ions from the water, in RO, the water is removed from the ions.  A combination of DI and RO is said to produce the highest quality water at a much lower operating cost per gallon.

Pure water advantages and window cleaning

Will water purification systems become ubiquitous in the window cleaning industry like scrapers and squeegees?  Most likely, according to manufacturers, distributors and end users we talked with around San Diego County and the U.S.
Safety and time savings are among the key advantages of using a water purification system, but it also results in spot-free glass. Tap water has high TDS content and when water evaporates, it spots the window, that is fact.  Water becomes more aggressive the purer it gets and is a natural detergent that helps loosen the bond of the dirt from the glass at an ionic level.  Between that and the mechanical action of the brush, that is why it cleans so well.  The reason it is spot free is that after a window cleaner brushes the frame and glass, they pull the brush back and give it a flushing rinse and then it dries.
No chemicals or cleaning products are required which is both economical and environmentally friendly.
Using a water fed pole and pure water systems boosts production by at least 50%.

Wave of the future
Is pure water use the wave of the future for window cleaning professionals?  Absolutely! Many companies are coming up to speed on it and many more will. There is always resistance to change though.  A window cleaner who has been cleaning window the same way for 30 years, just like his grandfather did, is hard to convince to start using pure water and a water fed pole.
Yes, using pure water to clean windows with will change the landscape of window cleaning but in no way will it replace the squeegee.