A Guide to Water Softeners


Although most drinking water in the United States is considered safe, there is increasing concern about the quality of drinking water as more and more pollutants are found in groundwater supplies. Worry about the possible health problems resulting from these contaminants is causing consumers to wonder what they can do to ensure the quality of their own water supply. The most strongly recommended and best solutions to the problem of a contaminated water source are either ending the practices causing degradation of the water source, or changing water sources. These options may not always be practical or may take months or years for completion. In the mean time, other solutions may be necessary. Installation of a home water treatment system may be one viable alternative for people with contaminated drinking water. It should be recognized that home water treatment is considered only a temporary solution. Treatment systems can be quite expensive, require regular monitoring and maintenance and no one system can be used for all contaminants. They may also become less effective if the degree or type of contamination changes over time. As a result, authorities recommend that bottled water be used for drinking and cooking purposes. This bulletin will provide a guide for consumers who want to know about home water treatment systems. The first step for a homeowner or renter with a suspected water quality problem is to obtain a chemical analysis of the water from a local health department or private laboratory. Public health professionals can aid in interpreting the results. It is important to remember that the presence of a contaminant does not always mean that treatment of the water is needed. A water quality professional will use the chemical analysis to determine which, if any, water treatment system is appropriate. Many water quality problems are of esthetic rather than health concern; e.g. bad odor or taste. Although these types of problems are important and may also be remedied using home water treatment systems, this bulletin will focus on contaminants which may lead to adverse health effects.

There are a variety of water treatment processes that are available to the homeowner. The systems differ in the types of chemicals removed, location within the home, and operating and maintenance requirements. Two broad categories of home water treatment units are point-of-use (POU) and point-of-entry (POE) systems. POU systems are installed near the point of use, normally in the kitchen at the end of a faucet, plumbed in-line under the sink, or placed on a countertop. These systems typically treat the 3 to 5 gallons per day which the average family uses for drinking and cooking. POE units are larger, more expensive, usually placed in the basement and treat water as it enters the home, generally excluding water to outdoor taps. POU or POE treatment systems are most economical if they are sized and operated to supply treated water only in quantities needed. POE devices offer the best protection from both esthetic and health related contaminants. However, POU devices are generally cheaper. POE devices are often preferred when iron or hardness is present. The presence of these compounds can discolor fixtures and clothes, or lead to excessive buildup of scale in water piping. There are several processes available for home water purification. These include activated carbon, ion exchange, reverse osmosis, distillation, chemical oxidation and ultraviolet radiation treatment. These processes purify water by removing contaminants or transforming them into less objectionable compounds. A major disadvantage of all the processes is that verification of performance can usually only be determined by expensive chemical analysis. Therefore, filter replacement or maintenance may not be performed when necessary. If the filter is not functioning properly, the water may contain unacceptable levels of contaminants. It is also not possible to know with certainty the degree of contaminant removal unless appropriate water testing has been performed.

Home treatment systems are not regulated by federal, state or local laws. Regulatory authorities generally consider home systems temporary solutions. This is because no system is capable of removing all possible contaminants and the potential for malfunction or improper maintenance is too great, in some cases, for these to be considered long term solutions. There is also no way for governmental agencies to monitor their performance in each home. Thus, to best protect public health, authorities recommend that permanent solutions, such as a new water source or clean up of the old source be developed. Certification of treatment products is available to manufacturers through independent testing laboratories, one of the most prominent being the National Sanitation Foundation (NSF). Results from NSF tests provide good measures of the effectiveness of devices designed to treat water for both esthetetic and health reasons. Those interested in particular systems can contact the NSF to determine if these devices have certified for the use intended. The Water Quality Association (WQA), a self-governing body of manufacturers and distributors, offers voluntary validation programs and advertising guidelines to their members. However, certification, registration or validation may be misleading. For example, manufacturers may be certified by an organization which used test conditions ideal for contaminant removal, but not representative of home conditions.


Activated Carbon

Activated carbon (AC) is commonly used to remove organic contaminants from water. Common organic contaminants are pesticides, industrial solvents such as trichloroethylene, and components of gasoline such as benzene. The contaminants interact with the large surface area of the AC by a process called adsorption. AC has also proven effective for removal of radon and many natural organic compounds which can cause unpleasant tastes and odors. AC treatment systems use replaceable cartridges containing granular or powdered block carbon. Cartridges with the most carbon remove the most contaminants and last the longest, thus increasing the time between cartridge replacement. Tests show that under-the-sink models have more carbon, greater convenience and better performance than faucet and countertop models. Cartridge life expectancy can be maximized, and replacement costs minimized, with systems that allow dispensing of unfiltered water at the tap for purposes other than drinking or cooking. The following considerations are important when purchasing AC filters;

1. Contaminant removal efficiency,
2. Ease of cartridge replacement
3. Effectiveness of attached sediment filters, which prevent cartridge clogging
4. Amount of pressure loss at the faucet caused by the filter
5. Risks associated with possible bacterial growth on AC.

Ion Exchange

Ion exchange works by exchanging a compound in the water for a chemical on the filter resin. It is effective for treatment of ions or charged contaminants. Most inorganic compounds can be removed by ion exchange, however, most common organic compounds cannot effectively be removed. Ion exchange is most commonly used to remove compounds which are of esthetic rather than health concern. Water softeners are the best known examples of ion exchange systems. Water softeners soften water by removal of calcium and magnesium which make water hard. These hardness ions in water are exchanged for the sodium ions attached to the resin surface. The water softener will no longer be effective when all sodium ions on the resin have been replaced by hardness ions. At this time, it is necessary to recharge the resin with sodium. This is accomplished by flushing the resin with high concentrations of salt (sodium chloride). There may be some health risks associated with consuming the exchanged sodium ions from home water softeners for people with high blood pressure and heart disease. These people should check with health professionals to determine if their maximum allowable intake of sodium will be exceeded by using a home water softerner. Ion exchange systems have also been developed for removing nonhardness chemical ions, such as nitrate and metals. Recharging the resins, in these cases, can only be done at special facilities, making this form of treatment expensive.

Reverse Osmosis

Reverse osmosis (RO) is a membrane separation process, employing a very thin membrane which allows water through but not various undesirable chemicals. RO membranes can remove all major types of contaminants including bacteria, metals, nitrate, and organics. However, there are some organic chemicals that may not be removed very efficiently. A RO system works by applying a high pressure to the contaminated water, forcing pure water through the membrane. Pure water collects on one side of the membrane while pollutants accumulate on the other side. The pollutants are periodically flushed to the sewer or septic system. RO membranes should last at least one year before replacement is needed. The typical RO system consists of: a sediment filter which protects the RO membrane, the RO module, activated carbon (AC) prefilters to remove chlorine for chlorine sensitive membranes, AC postfilters to remove some organics, a tank for water storage, and provisions for waste flow to drains. RO units are generally located at the point of use because of the small volume of water treated. They are typically located under the sink or on the countertop. Pretreatment with water softeners is often recommended for extremely hard water. Regular replacement of pre and postfilters is required. An important factor to consider regarding RO is the large volume of water that is wasted. This can be on the order of 25-60 gallons per day, depending on the amount of treated water needed and the pressure drop across the membrane.


Distillation relies on evaporation to accomplish water purification. It removes inorganic compounds, such as lead and nitrate, and some organics which do not easily evaporate and so are left behind in the distillation process. During distillation the water is heated to form steam. The steam is cooled and condenses to form purified water. Unevaporated contaminants are left behind and periodically flushed to the septic or sewer system. Distillers are POU systems and may be countertop, wall mounted, or placed on carts. Systems can be manual, partially or fully automated. Some models can separate volatile organic compounds before distillation. An advantage of distillation for use on water supplies which have not been chlorinated is that disinfection occurs during boiling. Care must be taken to avoid recontamination of the condensed purified water in the storage container by bacteria. Problems associated with distillation include loss of beneficial minerals from water and water that may taste flat. Operating costs may be higher than other forms of home treatment. Production of heat from a distiller may be beneficial in the winter but a disadvantage in the summer.

Chemical Oxidation

Chemical oxidation works by chemically changing the pollutant to a compound that is less objectionable. Chemical oxidants also act as disinfectants by killing bacteria and viruses. Chlorine is a common oxidant which is added to most public water supplies for disinfection purposes. There are several strong oxidizers which may be practical for home water treatment of a bacteria contaminated water supply. These include hypochlorite or hypochlorous acid and hypobromite or hypobromous acid. They are available in powder or liquid form. Automatic feeders are used to add the chemicals directly to water in the pipes. They can be either point of use or point of entry systems. Adequate contact time is essential to ensure disinfection. Chlorinated oxidants can impart an unpleasant taste to the water and may produce potentially harmful chlorinated organics (trihalomethanes) by reacting with natural organic materials present in the water. Ozone is another chemical oxidant. It can destroy bacteria in drinking water without creating the taste and odor problems common with chlorine. In addition, many organic compounds can be partially or completely oxidixed by ozone with no formation of chlorinated compounds. The effectiveness of an oxidant can be influenced by water temperature, acidity, concentration of oxidant, contact time with the oxidant prior to water use, and other factors. Pretreatment may be required for turbid water.

Ultraviolet Radiation

Ultraviolet (UV) radiation disinfects drinking water by killing microorganisms. Sufficient levels of UV radiation must be applied or it may merely retard growth or impede reproduction of bacteria and viruses, rather than destroy these organisms. UV systems are placed directly into water lines at convenient locations for POU or POE treatment. UV should be the final treatment if it is combined with other technologies. The other devices can remove dissolved and undissolved materials which inhibit the disinfection process and UV can kill any bacteria left in the system. A UV disinfection system consists of a prefilter for sediment removal in addition to a UV-emitting lamp. Good designs should provide:

1. Maintenance with easy tube and lamp removal
2. Flow rates that provide adequate contact time between radiation and bacteria
3. Easy visual inspection of the lamp and tube.

The primary advantage of UV treatment is that no disinfecting chemicals are added. Taste and odor problems are less likely to arise when chlorine is not added. However, chlorine provides residual disinfecting power downstream of the application point while UV provides no such residual.

Bottled or Bulk Water

Bottled or bulk water may be a viable alternative to home water treatment if it is needed only for a short period of time. It may be necessary during the time the homeowner is pursuing a new source of water or installing a home water treatment system. Bottled water is regulated as a food by the Food and Drug Administration (FDA). The FDA concerns itself mostly with sanitation and labeling but is also responsible for ensuring that bottlers comply with Primary and Secondary Drinking Water Standards. Only those bottlers working in more than one state are regulated by the FDA. In Michigan, the Department of Public Health (MDPH) regulates bottled water sources and the Department of Agriculture (MDA) regulates labeling and quality. Bulk water, delivered to the home and stored in large tanks, is available in some Michigan communities. This may be more convenient for some people.


There are many strategies for dealing with a water contamination term solution since no one system can work for all contamination problems and none are maintenance free. The homeowner or renter should take the time to learn about the water source and the treatment systems available to ensure an appropriate resolution of the problem.


1. Have a water analysis performed by a qualified laboratory.

2. Discuss your results with health professionals to
obtain their recommendations.

3. Research different products on the market, comparing initial and operating/maintenance costs, contaminant removal efficiency, company reputation, and service record.

4. Read manufacturer's claims and warranties carefully to make sure that the capacity and life expectancy meet your needs.

5. Understand the operation and maintenance requirements when the unit is installed. Find out where to obtain replacement filters and who will service the equipment when problems arise.

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Reprinted from The Michigan State University Extension. - Michigan State University Extension Home Page