Pure Water Creation and Use
Pure Water is created by removing the sediments and total dissolved solids (TDS) from the water. The process of making pure water involves a chemical and electrical process.

Small-scale systems use some combination of filters, membranes and resins to accomplish the task of creating pure (near zero TDS) water. Large scale systems use electricity to separate the dissolved solids from the water.

» Learn more about the different water purification methods

DI Cart? RO/DI Cart? How do I know when it is economical to buy/upgrade to an RO/DI system? » We can help you out!

Building cleaning uses small-scale water purification to create pure water. We say building cleaning because in most cases more than just the glass is cleaned when pure water is used. The window surroundings, adjacent building siding, exterior of gutters, and eaves can all be cleaned with pure water. Glass cleaning is the most demanding use of pure water for cleaning.
  1. Pure water used for glass cleaning should be less than 10 parts per million (10ppm) TDS.
  2. For Automobile and similar painted finishes the water should be less than 50ppm.
  3. For other building surfaces the water should be less than 70ppm
The ppm figures above are the upper ranges for cleaning in order to avoid visible water spotting on the cleaned surfaces.

De-Ionizing (DI) resin

The most important part of creating pure water is the electrical exchange process where the dissolved solids are removed from the water. In small scale systems, De-Ionizing (DI) resin is used to perform this process. The DI resin process uses positively and negatively charged resin particles to attract and capture the many different kinds of dissolved solids suspended in the water. DI Resin is made up of two styles of resin, one is an Anion resin the other a Cation. DI resin is stored in one or more tanks or cartridges. Water is passed through the resin and the dissolved solids are attracted to the resin. The water that leaves the tanks is pure. Some systems use separate tanks for the anion and cation resins, others are Mixed Bed tanks with both types of resin combined in a single tank.

As the TDS in the water is removed, the DI resin will eventually become saturated and stop attracting the dissolved solids. Therefore, the pure water stream should be tested frequently to insure the DI resin is still performing as expected.

The total TDS in the water varies considerably across the country. It can even vary within a city depending upon the source the water is derived from (well water vs. river water) and the type of minerals and other solids are contained in the water. DI Resin prices have fallen over the years, yet they are still expensive enough that some tap water can not be cleaned by the DI Resin alone in a cost effective manner.

De-Ionization is the key to pure water cleaning. Electrically removing the dissolved solids turns the water into a safe, yet effective cleaning agent.

But in some cases, DI Resin alone can get expensive:

An example of the costs of creating pure water is shown in this chart for the 3Star DI Resin Cartridge system:
  • 100ppm TDS (medium hard water) will cost about 12/gal. to clean
  • 200ppm (hard water) about 24/gallon
  • 400ppm (very hard water) about 48/gallon.

If we suppose that a the typical rate for cleaning glass is just less than a 1 gallon per minute, then a typical worker will consume 50 gallons an hour. Further, lets presume that the pure water is used for 6 hours a day, 20 days a month, and 12 months a year.

TDS per hour per day per month yearly
100 ppm   $6   $36   $120 $1,140
200 ppm $12 $74 $240 $2,280
400 ppm $24 $144 $480 $5,760

Lets also now figure that two houses per day are cleaned. We can then calculate the cost per house for the DI resin consumer. Each house would require: at 100pp - $18, at 200ppm - $36 or and at 400ppm - $72 in resin costs. $72 per house, when using DI Resin alone, is an expensive method of creating pure water.

So if the DI resin is the important component in pure water cleaning, then how can we extend the life of the product?

Multi-Stage filtering systems are the answer. These systems were developed to remove as much of the TDS prior to the DI resin electrical charge final polishing.

Multi-Stage filtering systems are generally made up of multiple filtering devices each designed to reduce the overall cost of creating of pure water and each contain at least:
  1. A sediment filter to remove larger solids like sand and rust flakes.
  2. A carbon filter to remove chlorine from the water supply and avoid damage to the RO Membrane.
  3. A Reverse Osmosis (RO) membrane to remove 90 to 97% of the dissolved solids.
Multi-Stage filtration requires high pressure to perform well, often input water pressure is enough to get the job done; however, pumps are required when input water pressure is below 40 PSI. They are also recommended for pressure below 60psi. The higher up the surface, the more pumps come into use. With water at 80psi and a surface at 2 stories, it is possible to clean without a pump. Beyond that there are several factors to consider: the number of cleaning devices and at what height the surface to be cleaned is. The typical pump is a 110V, but a 12v form is also avaibable for jobs requiring lesser capacity. All of the equipment in the catalog has some basic rating for what it is capable of.

This filtration system can reduce the cost of the water per gallon to 10% or less of DI resin alone. The savings in DI resin cost can pay for the RO/DI filtration equipment in as little a one to three years - depending on the total TDS of the in coming tap water.

When should I buy/upgrade to an RO/DI system?

It takes some knowledge and time to break into pure water cleaning.  There are several ways to get started.  We break it down based on the water conditions in your area:

Less than 150 TDS:
You can choose between DI Tank rental from a local company or purchase a DI Cart. Tanks are usually strapped to the back of the vehicle and hoses are run to and from the tank: one hose for the tap water in and another for the pure water out. DI Carts are often more manageable and resin refills can be kept in the vehicle to allow for quick replenishment (where tanks must be routed back to the rental company for recharge).

As your business grows, your expenses in DI resin will grow as well. When your monthly expenses for DI approach $200 a month consider upgrading to an Multi-Stage (RO/DI) system to drop the DI cost to about $20 or less - and put the other $180 a month toward the initial equipment investment. A $3,600 system will break even in 20 months and you will own your own water purification machine that will output pure water for less than 3 or 4 cents a gallon in consumable costs.

Above 150 TDS:
Your DI Resin cost per cleaning will be high enough that you should consider Multi-Stage (RO/DI) filtration from the beginning. Or, at a minimum, think about choosing a DI Cart system that is upgradable to Multi-Stage filtration as you build your business of pure water cleaned structures.


Multi-stage (RO/DI) systems use a Reverse Osmosis Membrane and a Carbon/Sediment filter together to remove 95-98% of the impurities from the water before it is run through the DI filter to "polish" it. Therefore, when you TDS is extremely high, this system will drastically help save the life of your DI filters, which is the bulk of the marginal cost.