We recommend a whole-house water purification system as an essential feature of the healthy home for most locations. Choosing the proper system will depend on several factors including location, budget, water use, and taste preference. No single filtration medium can remove all contaminants from all water.
Because water quality and individual needs vary, no single combination of systems will provide a universal solution.
Choosing a system can be a complex and confusing process. The average homeowner typically does not know the right questions to ask in order to get accurate information. Water filtration systems have become popular internet marketing products and many people selling them are not much more knowledgeable than potential customers about the range of needs and possibilities. We recommend that you consult with an individual who has the following credentials:
• a broad-based, longstanding experience with water quality in your area
• a wide variety of equipment from several manufacturers
• the ability to provide you with several options at various prices
• the ability to explain the pros and cons of each system
Water conditioners are used to improve the aesthetic quality of water, including color, corrosiveness, clarity, and hardness. They use a process of ion exchange to eliminate from the water undesirable substances (such as calcium and magnesium) that may precipitate scale on fixtures, laundry machines, hot water heaters, dishwashers, shower stalls, sinks, and skin. Water conditioners can also be effective in removing sediment, chlorine, and certain metals, such as low levels of manganese and iron (both of which can cause stains) as well as odor from hydrogen sulfide. Flow rate is affected by both the size and the design of the water softener and must be appropriately specified on an individual basis. Conditioned water is often referred to as “soft” water.
In the ion exchange process, calcium or magnesium ions are exchanged with either sodium or potassium. Sodium chloride is the more common regenerate for water conditioning, but many water treatment companies have switched to potassium chloride, which is widely believed to be a healthier and more ecologically sound choice. Potassium chloride is essentially a refined potash, and when returned to the ground water it can serve as a fertilizer for many plants. The small amount ingested daily from water conditioned with potassium is about equivalent to what you would gain by eating half a banana and can be a positive addition to your diet.
For those with a medical condition affecting electrolyte balance, blood pressure, or kidney function, we suggestyou consult a physician before you consider purchasing a water-conditioning system with salt-based regenerates. Potassium chloride may also contain traces of naturally occurring gross beta radiation.
Because of chloride discharge into city systems and the subsequent impact of chlorides on rivers and agriculture, some municipalities are moving to ban new salt-regenerating water conditioners and give rebates to customers who switch to salt-free systems. Municipal water and sewer systems are not configured to remove chlorides. This issue is of particular concern in dense metropolitan areas, but since the ion exchange process is also commonly used to remove water contaminants in private domestic wells, chlorides also are discharged into septic systems and ultimately into shallow aquifers.
One of the most promising developments in water treatment is the advent of chemical-free, nonelectrical, nonbackwashing, salt-free systems to treat hardness as an alternative to softening. In one system, which uses template-assisted crystallization, hardness minerals are attracted to a media nucleation site, which then sloughs off seed crystals that travel through the plumbing system in a molecular configuration not prone to accumulation as scale.
The single best source for verifying a manufacturers claims about any water treatment product is National Sanitation Foundation International (NSF), which is the industry’s gold standard for the testing and certification of water treatment systems and components. Before buying water treatment equipment, we recommend that you visit nsf. org and look up individual products and manufacturers to verify certification for efficiency and contaminant reduction.
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Type of system |
How it works |
What is eliminated |
What is not eliminated |
Comments |
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Carbon filters: There are countless varieties of carbon filters. The two most commonly used filters in water purification are described here. Granulated activated carbon (GAC) has an amazingly large surface area (up to 1,000 square meters per gram) for adsorptive activity. Carbon filters are not bacteriostatic and will become contaminated with use. Inexpensive sediment prefilters will extend life. Inexpensive chlorine tests can indicate when to change the filter if it is used with chlorinated water. These filters can themselves become a source of contamination if not changed frequently enough. Locate the tank away from inhabited areas when used to filter radon. Although carbon filters are less expensive than aeration systems, they can collect radioactivity and may require special methods of hazardous waste disposal. Aeration is preferable to carbon filtration for radon removal. |
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GAC (granulated activated carbon) |
Carbon is steam-treated so that the surface becomes pitted, thereby increasing surface area and adsorption capacity. |
Trihalomethanes, dissolved gases including chlorines, most pesticides, many chemical pollutants, radon gas |
Heavy metals, sediment, fluoride, viruses and bacteria, dissolved solids, and particulates, including radioactive particulate matter |
Requires that water have sufficient contact time with the filter. Because GAC can breed bacteria, it is most effective when used with treated municipal water. |
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Carbon block |
Powdered carbon is glued together to form a matrix structure that adsorbs contaminants. |
Trihalomethanes, dissolved gases including chlorine, most pesticides, many chemical pollutants, radon gas, particulate matter; can be used for heavy metals under some limited conditions |
Fluoride, nitrates, viruses, and bacteria |
Considered more effective than GAC if water conditions are within certain parameters. Will remove heavy metals only for a limited time. Periodic retesting is essential. Not recommended for most heavy metal removal. Glue content is a concern. Whole-house or point — source available. |
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Reverse Osmosis (RO) RO involves forcing water through a semipermeable membrane with extremely fine pores from a more concentrated solution (ultimately becoming the reject water) to a more dilute solution (the product water). The water’s direction of movement is the opposite of what would be experienced during osmosis and is achieved by applying water pressure to the solution on the more concentrated (contaminated) side of the membrane. RO will remove a variety of ions and metals as well as some bacterial contaminants (cysts), but not coliform bacteria. RO systems will remove some arsenic (arsenic V but not the more toxic arsenic III). Reverse osmosis is well documented in the literature and in post-treatment testing proves to be effective in removing uranium, but N5F does not certify for uranium reduction. RO membranes eject the bulk of almost any dissolved and suspended contaminant including ionic, organic, and silica compounds. One criticism of reverse osmosis-filtered water is that it is stripped of essential minerals. Although this is true, it is a tradeoff for overall water quality. Most consumers do not depend on water for their nutritional needs but elect to take vitamin supplements or remineralize their RO water. Savvy water treatment companies use a crushed limestone (calcite) post-RO filter to impart a pleasant taste to the water. Parents sometimes express concern that RO removes fluoride added to municipal water for dental health purposes. This is true, but water fluoridation in general is a controversial issue and today most children under professional dental care receive whole-mouth fluoride treatments. |
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Type of system |
How it works |
What is eliminated |
What is not eliminated |
Comments |
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The most valid criticism of RO is that anywhere from 3.5 to 5 gallons of water are rejected for every gallon of purified water produced. Many inexpensive, noncertified RO systems have much higher rejection rates, are extremely wasteful, and still do not deliver verifiable contaminant reduction, the primary reason for using reverse osmosis. While reject water is routed to the drain, it is not lost but reenters the hydrologic cycle. In many cases, the RO reject water may be collected and redirected for irrigation purposes. Seek out a five-stage RO system. Plastic parts can be problem for individuals with petrochemical sensitivities. When selecting a reverse osmosis system, look for certification by National Sanitation Foundation (NSF) International (www. nsf. org) to ensure materials quality, system performance, and contaminant reduction. Be wary of self-proclaimed lists of contaminant reduction and verify the certification for the specific unit you are considering on the NSF website under Drinking Water Treatment Units. |
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СТА (cellulose triacetate) RO membrane |
Water is forced under pressure through a fine membrane that screens out dissolved solids. |
Dissolved solids (60 to 90%), heavy metals, asbestos, radioactive particles, some bacteria; NSF certified undercounter RO removes 99.99% of cysts |
Dissolved gases, some biological contaminants, sediment |
Most suitable for pretreated municipal water in which biological contaminants are already low. Filter requires chlorinated water supply to prevent bacteriological decay. |
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TFC (thin film composite) well membrane |
Same as above. |
Dissolved solids (60 to 98%), heavy metals, asbestos, radioactive particles, some bacteria, limited amount of biological contaminants |
Dissolved gases, sediment |
Cannot be used with chlorinated water supply unless prefiltered with carbon. |
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Sterilization |
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Ultraviolet (UV) purification |
UV radiation penetrates membrane of microbe and inactivates it. |
Biological contaminants |
Dissolved gases, sediment, radiologicals (note that protozoan cysts such as Giardia and Cryptosporidium may not be completely eliminated if there is any shadowing effect caused by hardness or sediment) |
Does not provide residual disinfection. Sediment, hardness, minerals, iron, manganese, or turbidity will make system ineffective because a shadowing effect shields bacteria from UV. |
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Oxidation with ozone, hydrogen peroxide, chlorine, or injected air |
Oxidation can change the valence state of water contaminants so that they can be physically filtered. |
Clarifies, deodorizes, and precipitates metals; oxidizes and eliminates bacteria, viruses and organic matter |
VOCs, pesticides, chlorine; does not remove anything from water |
Use of chlorine as oxidizing agent not recommended from ecological and health standpoints. Post-system carbon filtration is recommended. |
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Type of system |
How it works |
What is eliminated |
What is not eliminated |
Comments |
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Others |
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KDF (kinetic degradation fluxation) |
Zinc/copper alloy causes chemical transformation of contaminants as they pass through KDF, which disrupts metabolic function of bacteria. |
Controls bacterial growth; removes some heavy metals, chlorine, and biological contaminants |
Trihalomethanes, bacteria, radiologicals |
Very effective when used as prefilter, followed by carbon filter and then reverse osmosis. Does not work well in all pH conditions; requires 150 ppm of total dissolved solids (TDS) to be effective. Is bacteriostatic but not a bactericide. Suitable for water with very low bacteriological count. Works best on hot water. Testing after installation is advised. |
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Shower-head filters |
Small filter/shower head combination that threads into existing plumbing. |
Chlorine. Some filters may have other properties. Verify contaminant removal potential at www. nsf. org. |
Radiologicals, pesticides, gasoline, bacteria. Do not remove trihalomethanes, pesticides, or VOCs because of lack of contact time. Not considered effective treatment for most biological contaminants or chemical contaminants of health concern. |
Very inexpensive and often very limited in scope. Do not require plumber to install. See May 2007 Consumer Reports for reviews of shower head, pitcher, carafe, and other inline filters. |
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Distillation |
Water is turned to vapor, condensed, and then collected. |
Dissolved solids, microorganisms, nitrates, heavy metals, sediment, radioactive particulate matter |
VOCs, dissolved gases, including chlorine |
Effective when used with carbon postfilter. High maintenance, low production, and high energy consumption. Flat taste. Metal-bodied distillers may add aluminum or other heavy metals to water. |
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Sediment filters |
Can be a filter medium in cartridge or tank applications. Can be a settling tank where water is siphoned off the top after particulates sink. |
Particulate matter, sand, dirt |
Remove only particulate matter; strictly a physical process |
Most often used as prefilter for other systems. Backflushing models use additional water for self-cleaning. |
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Type of system |
How it works |
What is eliminated |
What is not eliminated |
Comments |
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Aeration |
Water is run over a series of plates, where it is depressurized and blown with a fan so that gases and odors can escape. It is then repressurized. |
Radon, odors, dissolved gases |
Bacteria, solids, heavy metals, and dissolved radiologicals |
Aeration is the EPA — preferred method for radon removal. |
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Centralized Water Purification |
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Ultrafiltration |
Water pressure pushes water molecules toward the hollow center of fiber membrane tubes. Large particles and microorganisms are trapped within the fiber and then flushed out during automatic backwashing. |
Removal of chlorine by activated carbon and physical blocking of bacteria, parasites, and viruses greater than 0.02 microns |
Heavy metals, radioactive particles, arsenic, and nitrates |
Ultrafiltration is touted as eliminating the need for bottled water, but it is far less effective for contaminant removal than RO. Ultrafiltration systems do not soften water and do require water backwashing. |
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Authors note: This table has been created by Steven Wiman of Good Water Company for this edition of Prescriptions for a Healthy House. |
Much has been written about the energy efficiency of appliances. Since appliances account for as much as 30 percent of household energy usage, choosing wisely can greatly reduce energy consumption. Because many sources of information are available on appliance energy values, we have limited discussion in this book to health issues related to appliance selection. (See the end of this chapter for books about reducing appliance energy consumption.)
