This is an updated version of the product training course introduced by Supply House Times in 1979, authored by Don Arnold.

All of our discussions about water-using products up to this point have had one fundamental assumption in mind: that a good quality water supply is available to serve them. Unfortunately, it isn't that simple. First of all, except for the distilled variety, there is no such thing as "pure water." Certainly, nothing like that runs through our residential pipes. By definition, the word "pure" means a substance not mixed with anything else, and the water we use every day is mixed with a combination of "something elses." Let's look at the products available to deal with them.

Chemical Feeders

While the majority of residents in our country are served by a municipal treatment plant where chlorination takes place, about 15% of the population derives its water from private supplies (wells). When the quality of such supply is below acceptable health standards, it is common to disinfect the water by use of an "in-house" chlorination system. Typically, the product involved here is a chemical feeder, a dispensing device which automatically releases small amounts of chlorine into the incoming water supply. Dosage of chlorine is defined in terms of "parts per million," which refers to the ratio of dilution with the water (you will sometimes see this abbreviated as "ppm"). In addition to disinfecting biologically harmful substances from water supplies, chemical feeders are also used to remove objectionable sulfur content by means of chlorination. Water with high levels of acidity is another application for a chemical feeder, in this case by dispensing a highly alkaline compound such as soda ash to provide neutralization.

Water Conditioning (Softening) Systems

Of all the water treatment products or systems discussed in this section, these are among the most widespread in residential use today. Why does water need to be softened? In nature's cycle, water comes down from the clouds as rain, and after reaching the ground, filters on down to the water table. While passing through the ground, there are a number of minerals dissolved and carried along in the process. Certain minerals are more easily dissolved than others, and two that dissolve most readily are the salts of calcium and magnesium. Since the mineral makeup of soil varies widely between parts of the country, this accounts for the fact that water is characteristically hard in some areas and naturally soft in others. The water softener's function is to remove calcium and magnesium (and to a much lesser degree, iron) from a water supply by a process called ion exchange. The unwanted minerals in water supplies take the form of ions, which are electrically charged atoms, or groups of atoms. Calcium and magnesium ions are the "bad guys," since they combine with soap to leave a residue of scum which clings to fixture surfaces and clothing fibers. When heated, these ions leave the water (crystallize) to form scale on piping and tank surfaces. In an ion exchange system, the unwanted calcium and magnesium ions are traded for wanted ones, the sodium ions. The typical water softening system includes two tanks ? one containing a resin for the exchange process, the other containing salt brine (a salty solution). In the first one, a column or "bed" of granulated resin particles is initially charged with sodium ions. However, the resin has a greater attraction to the magnesium and calcium ions than to the sodium ions originally present; so, as the incoming water passes through the bed, the sodium ions are "bumped off" and replaced by the calcium and magnesium variety. Thus, the "bad" ions stay in the resin exchange tank, while the "good" ions pass out of the tank to the points of use in the house or building. This process continues automatically until the supply of sodium ions in the resin bed is nearly depleted. This is where the other tank we mentioned comes into the act. If our bed of resin exchange material is to become effective again, we must regenerate or "recharge" it with more sodium ions. To do this, we wash the resin material with a strong solution of salt brine. Though the resin has a greater attraction to the calcium and magnesium ions, they are overpowered by the greater concentration of sodium ions and are thus "kicked off" to be flushed down the drain. Most water softeners sold today are the automatic type, meaning that there is a mechanism that initiates the regeneration cycle, and moves it through each step involved without need for manual tending. Some are triggered by timers, others by actual consumption.

Filtration Products

This is the area of water treatment where there seems to be the most confusion today. Even the common labels are confusing. For example, the term purification is often applied to a wide range of products, but technically, should be used only to describe devices or systems that produce totally pure water (only distillation qualifies for this). Even the word filtration can be misleading, because it technically refers to processes involving a physical straining or adsorption of suspended contaminants, which would not accurately describe reverse osmosis. Starting at the beginning, why, if we have disinfected the water through chlorination, and softened it through ion exchange, do we need to do anything else to it? It's because the above processes do nothing to improve the taste and odor qualities of water (if anything, chlorination tends to add to or amplify objectionable qualities). They also do not eliminate non-organic toxins ? things like THMs, TCEs, lead and asbestos. And finally, as we see in the news from time to time, municipal disinfection treatment can fail, causing outbreaks of things like cryptosporidium.

Sorting Out The Technologies

There seems to be much misunderstanding today over what the various product options are and what they can do. Following are the basic sub-categories:


Though this may seem redundant if we are assuming a water supply already disinfected, there is growing use of in-house backup protection. The most common product options for this are ultra-violet (exposing passing water to UV rays) and ozone generation (converting oxygen in the water).

Physical Filtration

The most widely sold technology in this field today, filtration is a process that essentially strains and/or adsorbs chemicals, tastes and odors from the water. The most common medium for this is carbon, which can take a granulated or solid block form (tubular profile). Porous ceramic cartridges (also tubular) are another option. These technologies are sometimes used in combination, along with other additives, such as silver. With multiple sump designs, it is common to have a "pre-filter" that essentially strains out the "big stuff," to keep it from overloading the finer filtration cartridges downstream.

Reverse Osmosis

This concept involves forcing water through a semi-permeable membrane which allows the water molecules to pass, but not the dissolved solids (typical removal in the 85% to 95% range). Though more effective than most filtration systems, there are some key installation and operating differences to be aware of. In conventional R.O. systems, the process requires several gallons of waste water for every gallon of good water produced. For this reason, an R.O. system also requires a drain connection (with the water routed through an air gap above the counter). Because the process is relatively slow, the system requires a storage tank to provide an adequate amount for delivery at any given time. Though the basic R.O. system does not require periodic changing of cartridges as in the case of filtration, they are most often equipped with a carbon filter (for taste and odor purposes) that does require such servicing.


As mentioned, this is the ultimate in water purification. In the phase change cycle of converting water to steam and back to water again, virtually all impurities are removed. Like reverse osmosis, this is a relatively slow process that requires storage of the resulting drinking water.


The College of Product Knowledge ran in Supply House Times for three years and resulted in a reprint manual that sold for many years to follow, totaling thousands of copies. It became something of an industry classic. Much of the original training material is still applicable to the products sold today --but there is also much in the wholesalers' product mix that is new since then. The purpose of this updated series is to look at what has come along since the first edition.