From the complex to the simple, there are many types of home water filters available today. Water purification and filtration systems come in an assortment of styles, types, and price ranges, to suit every need. From pitchers to faucet filters, countertop models to whole-house devices, they are typically less expensive and much more convenient than buying filtered, bottled water.
The simplest home water filter device may be the water-filtering pitcher. A person just fills the pitcher's special reservoir lid with tap water, and as the water runs through the filter into the pitcher, many minerals and contaminants are removed. The pitcher can be stored in the refrigerator to keep the drinking water cold.
Simple-to-use, easy-to-install home water filters that attach right to the tap are also available. These are small canister filters containing carbon and other materials, which have a fitting to connect to the faucet spout. They are designed with a bypass valve to filter water only when necessary, such as for drinking or cooking. One click of the canister knob will provide filtered water, and the other will give water for ordinary uses such as cleaning the sink. Most cartridges are rated between 100 - 300 gallons (378 - 1,135 liters) and have built-in indicators to alert the user when the filter is exhausted.
A larger cousin to faucet filters are purification systems that sit on the countertop or under the sink. A water line feeds into the filter, and a small spout delivers purified water. Some work through reverse osmosis (RO), while others are ion-exchange filters, which are the only type that can completely remove calcium and magnesium, which cause lime scale. Canisters might be costly to replace, and they will exhaust quickly in areas with hard water. Ion-exchange filters can also come in smaller, less expensive units, and they are even built into some coffee makers.
Of the countertop or under-sink home water filters that are RO filters, these use a dual-canister system: One canister is a particle filter and the other is a carbon filter. While these eliminate virtually all impurities, they also have some drawbacks. Making 1 gallon (3.78 liters) of RO water can take up to 10 gallons (38 liters) of tap water, depending on the local water supply. The "runoff" water is very hard, containing all the minerals removed from the purified water, and normally goes down the drain. Some people design a retaining tank to circulate this "wasted" water to a washing machine or put it to some other use. RO makes the purest, softest water possible, at the highest price. It removes all contaminants, salts, and minerals, including additives like fluoride.
Water distillers have long been popular ways to filter water. They boil water until it becomes steam, which is then reconstituted into pure, clean water. Distillers are larger than some other water filters and are often connected to the water supply at the sink.
People who are really concerned about the quality of their water may want to consider purchasing a filter that connects directly to the main water line. In this case, every outlet in the house, including the shower and bath, will receive purified water. Some agricultural regions in the US require this type of filtering system by law, due to pesticides in the water table. These are also RO systems, and produce extremely soft, pure, distilled water. Systems of this type are large and of all the home water filters, they are the most expensive; however, many people feel they are well worth the cost since they ensure safe, clean water throughout the entire home.