Most municipal water sources are safe for consumption, but the chemicals used to treat the water may leave an unpalatable aftertaste. And some private water sources may, at times, contain unhealthy levels of certain contaminants. Both issues can be resolved with a home water filtration system. Determining which system is best for your home depends on your current water quality. Before purchasing a filtration system check with your local Department of Public Works or the EPA website for your city's water quality report.
Once you know what issues you need to address, consider one of these options for home water filtration:
Faucet-Mounted Filter. Most faucet-mounted systems use a carbon filter. Carbon is a porous material that absorbs impurities as water passes through. These filters remove lead, PCBs, chlorine byproducts, certain parasites, radon, pesticides, herbicides, MTBE (a gasoline additive), trichloroethylene (a dry-cleaning solvent), some volatile organic compounds (VOCs), certain pharmaceuticals, and some levels of bacteria. You will need to check the filter package for more specific details about what it removes. It's best to select one labeled as meeting NSF/ANSI standard 53. A filter that is NSF-certified is third party verified to reduce health-related contaminants under specified conditions. For most people an activated carbon filter with NSF Standard 53 certification will be enough.
Reverse-Osmosis System. If your water quality report shows you need a greater level of filtration, a reverse-osmosis system may be a better option for you. Installed under the sink, these systems treat water as it comes into the home. Reverse-osmosis systems push water through a semipermeable membrane that works as an extremely fine filter removing impurities. Often used in conjunction with a carbon filter, these systems remove all the contaminants listed under faucet-mounted filter, plus perchlorate, sulfates, arsenic, barium, nitrate/nitrite, fluoride, industrial chemicals, heavy metals (like cadmium, copper, and mercury), chlorides, certain parasites, and pharmaceuticals. Unfortunately, these systems waste a significant amount of water during the filtration process – 4 to 9 gallons (15 to 34 liters) of water for every gallon (3.8 liters) filtered. Some systems will store that used water and re-purpose it for toilet flushing.
Ultraviolet Light Unit. In the rare case that your tap water contains unsafe levels of bacteria, an ultraviolet light unit can help. These under sink systems use high frequency light to kill living organisms. Class A systems kill bacteria, viruses, and parasites. Class B systems reduce nuisance microorganisms and are not intended for disinfection. It is recommended these systems be used in conjunction with a carbon filter to remove additional contaminants.
While your water quality is a (if not the) major factor is selecting a system, it's also important to compare initial purchase price, installation, filter prices, and other operating and maintenance costs. Faucet-mounted filters cost $20 to $50 and require a replacement cartridge that costs about $10 every three to six months (more often if you have hard water). Reverse-osmosis systems can range anywhere from $100 to $1,000 depending on size and quality. The membrane must be replaced every two or three years for $100 to $200 and filter cartridges every six months for $40 to $100 each. An ultraviolet light unit can cost anywhere from $100 to $300 for a basic, self-installed unit to $700 to $900 for a whole-house, plumber-installed system. The filter and lamp must be replaced annually for about $150.
Regardless of which option you choose, it will have to be properly maintained to be effective. Make sure to follow the manufacturer's maintenance directions to keep your water filtration syetem working properly.