Most point-of-use filters are equipped with carbon filters that trap impurities and also remove odors. They can be in the form of pitchers that are filled and kept in the refrigerator -- this offers the added advantage of keeping the water chilled -- or in units that process the water as it exits a faucet. As opposed to point-of-entry units that clean a home's entire water supply, pitchers and faucet-mounted water filters clean only the water obtained or used in a particular area.
Holding from 5 to 10 cups of water at a time, the average-sized water filter pitcher uses gravity to pull the water down through the carbon layer into the reservoir below, a process that takes roughly 5 to 10 minutes to complete before the water is considered drinkable. Larger models hold up to 18 cups and feature a dispensing spigot. Drawbacks to water filter pitchers are making space on a refrigerator shelf for them and locating brands, such as Brita or Pur, that do not contain bisphenol A (BPA) -- a chemical found in many plastic products that may cause health-related problems.
Faucet-mounted water filters provide a continuous supply of clean water without having to sacrifice refrigerator storage space. Some are simply carbon enclosed in plastic cartridges while others feature layered carbon that traps impurities. Faucet filters are equipped with valves that allow users to switch to an unfiltered setting, as they can be weakened by frequent hot water usage. Drawbacks include a reduction of water flow rates, the filter getting in the way of performing other tasks in the sink (such as doing dishes) and the difficulty of installing the filters on certain types of faucets.
All water purifying systems use some type of filter, which you must replace periodically to maximize their benefits. In some cases, the cost of the filter can be prohibitive, a consideration when deciding which type to buy. Generally, the filters used in pitchers are less expensive but may need replacing more often, depending how often the pitcher is refilled. Faucet-mounted filters can be pricey and can represent a significant investment depending on their frequency of use.