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ArticleTechnical Article

Water Softeners

By HHI Staff

A water softener is popularly defined as any substance or device that is able to eliminate, or in some way inactivate, hard-water minerals that are commonly found in water supplies. It should be noted that hard water is usually defined as having a dissolved calcium and magnesium concentration at or above 120 mg per liter. However, many people find that a concentration of only 85 mg per liter still creates some of the problems associated with hard water.

 

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What are some typical hard-water problems? One is the crusty white buildup that can occur on the interior of your plumbing fixtures and water pipes. This lime scale is actually formed by the minerals precipitating (coming out of solution). Another problem is that calcium and magnesium minerals in water can react with the fats and oils in the soaps you use, creating an insoluble scum known as soap curd. In addition, white fabrics washed in hard water can acquire a grayish tinge.

Although most people use the term “water softener” to mean anything that can counter the effects of hard water, you should be aware that there’s a technical distinction between the terms water softener and water conditioner. Water softeners are devices that add a substance to the water to eliminate or inactivate hard-water minerals, while water conditioners are devices that don’t add anything to the water. On the other hand, water-softening agents are simply substances (not devices) that one can add to water to deactivate or eliminate hard-water minerals. (Note: Some water-softening devices help remove or inactivate iron and certain other minerals besides just calcium and magnesium.)
Water-Softening Agents
Certain compounds, when added to hard water, act as water-softening agents. What they actually do is combine with the dissolved minerals, causing them to precipitate (be pulled out of solution), thus creating very minute insoluble solids. This process, known as water softening through precipitation, causes the hard-water minerals to be chemically bound up so that they’re no longer free to react with soap to form scum (soap curd), or to attach themselves to the interiors of pipes, etc. and form lime scale.

Today, borax and sodium carbonate are two commonly used water-softening agents. For many years phosphate compounds were very popular for this, including trisodium phosphate (TSP) and sodium hexametaphosphate. However, because it was determined that phosphates can create water-quality problems in streams and other waterways, their use has declined dramatically. In homes, water-softening agents are generally point-of-use products. In other words, they’re not typically added to the entire water supply of the house, but usually just to your laundry’s wash water.

Typical Water-Softening Devices

Water-softening devices were created to provide continuous whole-house water softening. They work through a cation exchange process (cations are positively charged atoms). Simply put, positive sodium ions are used to replace the positive hard-water mineral ions in your water supply. The source of the sodium ions is a brine solution made up of common salt (sodium chloride) and water. Because these units add a substance (salt) to change the hardness of the water, they’re not considered water conditioners.

In practice, a typical water-softening device is able to soften your water relatively quickly because it also contains a catalyst (a substance capable of speeding up a chemical reaction while not being changed itself). At one time, zeolite granules were commonly used as the catalyst in most home water-softening devices. However, these days, beads of a synthetic resin (such as polystyrenated bivinylbenzene) are much more popular. These catalysts provide the surfaces on which the ion-trading takes place. Because a catalyst is never altered or used up, the synthetic-resin beads (or zeolite) never need to be replaced. However, their surfaces will eventually become clogged with mineral ions. When that occurs, the ion-exchange process (the softening process) slows dramatically and a recharging cycle becomes necessary.

In practice, the recharging process includes several steps. First, there is a backflushing of the water flow, which loosens the mineral buildup on the catalyst’s surfaces. Then, there’s an addition of fresh brine solution. The final step is a complete rinsing of the tank containing the catalyst with fresh water to remove the loosened minerals. Most home water-softening devices recharge themselves automatically. However, salt will have to be added manually from time to time. The actual frequency for this will depend on your particular water softener, the hardness of your water and the volume of water used daily in your household.

Most typical water softeners that use salt will produce water that feels slick, suds easily and creates no mineral buildup (lime scale) in your pipes or on your plumbing fixtures. However, there are negatives to these units. One is that the recharging process “wastes” a certain amount of water by flushing it down the drain. Water-softening devices can also be fairly expensive, but some companies offer lease and rent-to-own programs.

 

You will have to routinely purchase salt for your softener. Fortunately, arrangements with your softener dealer can easily be made to have salt delivered directly to your home. Some dealers will even fill the salt tank for you. Of course, there’s a cost to all this (the cost may actually be included in your purchase or rental price). To save money, you might purchase the salt you need at a local chemical-supply company, or at a wholesale or discount outlet, and periodically fill the salt tank yourself.

Still another concern with typical softening devices is that, because they use salt, the treated water will have a relatively high sodium content. This can be a real concern for individuals on a salt-restricted diet. However, if you install a reverse-osmosis unit in your kitchen with a membrane rated to remove salt, your drinking and cooking water will contain a much lower salt concentration. Of course, distillation will remove virtually all the salt.

A few local jurisdictions have apparently prohibited the installation of automatic, self-regenerating (backwashing) water softeners that use sodium-chloride salt-ion exchange. This is because the water drained from these devices during their cleaning cycle eventually enters the sewer lines and ends up at water-treatment plants. Treating this salt-laden backwashing water has proven difficult and expensive. Therefore, check local codes and regulations before purchasing a water-softening device. (Note: Some units now use compounds such as potassium chloride rather than sodium chloride.)

 

From Creating a Healthy Household: The Ultimate Guide For Healthier, Safer, Less-Toxic Living, © 2000 by Lynn Marie Bower. Used by permission.

 

 

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Water Softeners:  Created on February 24th, 2007.  Last Modified on February 27th, 2011

 

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