Activated Carbon Filters

Activated carbon filters absorb impurities as they pass through a carbon cartridge. Generally, they are used to eliminate undesirable odors and tastes, organic compounds and to remove residual chlorine. Most inorganic chemicals, metals, microorganisms and nitrates are not removed by the filters.

Carbon filters also remove some potentially hazardous contaminants such as radon gas, many dissolved organic chemicals and trihalomethanes. If low levels of these contaminants exist, a whole-house unit can be used. However, these filters are not designed to remove persistently high levels of these contaminants. When contamination cannot be eliminated, an alternative water supply may be the safest solution.

The carbon filter loses its effectiveness as it becomes saturated with contaminants and must be replaced on a regular basis. Using the filter longer than its rated lifetime may cause contaminants to be flushed into the drinking water. Before purchasing the unit, ask the dealer if the filter can be replaced, the frequency of replacement, where replacement filters may be purchased and how much they cost.

The material in an activated carbon filter provides a growth surface for certain bacteria. If the filter has not been used for five or more days, simply run chlorinated water through the filter for at least 30 seconds before use.

Carbon filtering devices use carbon cartridges that have a porous surface. This allows the cartridge to absorb a variety of substances, including THMs, odors and disagreeable tastes. A filter's effectiveness depends on the amount of carbon in the unit and how long the water stays in the unit. The longer the water is in contact with the filter medium, the more time the carbon has to remove impurities. Those packed with a large volume of charcoal generally remove more organic material at the beginning of the cartridge life. Performance tends to decrease less rapidly over time than it does for those containers with a small amount of charcoal.

• Faucet-mounted filters attach to a faucet after the aerator is removed.
• There are two basic designs. One uses a by-pass valve that filters only water for cooking and drinking. The second design has no by-pass valve; all water flowing through the faucet is filtered. Some models are placed on a counter and have a hose running from the faucet to a charcoal filter. They are not permanently attached to a faucet.
• Pour-through (portable) filters freshen water on recreational vehicles, on boats or at campsites.
  One should be certain that the water started with is suitable for drinking (potable water). This type, if not powered, is the simplest of all. Water poured through the filter flows into a container. A few models, however, are powered and operate on a 115-volt current; others operate on a 12-volt line or battery. These units increase the rate of filtration. Not all water filters need power to perform, such as the Whirlpool Water Filters which can be purchased at many local department stores, and various online water filter outlets. Some of those operating on a 12-volt battery can filter up to 1-1/4 gallons (4.7 liters) in two minutes.
• Specialty-type filtering devices such as ice maker and scale filters are placed on the cold water supply line to appliances.
  Ice maker filters are attached to the cold water line to refrigerators or standard ice makers. Scale filters are connected to the supply line of water heaters or humidifiers.
• A line by-pass filter may be installed in one of two locations.The first location is beneath the sink where it is attached to a line leading to a separate faucet at the kitchen sink. The second location is in the water line after it enters the house. The latter requires installation of a valve in the water line ahead of the filter in order for the water that is drawn from the regular faucet to be shut off.
• A stationary water filter is installed in the cold water line under the sink. All cold water flowing through the pipe to the kitchen is filtered.