Sediment filters remove large particles by trapping them in a replaceable paper or fabric cartridge as the water flows through. They ignore microbes, organic compounds, inorganic compounds, and metals.
Ozone filters remove most microbes and organic compounds. They ignore inorganic compounds and metals.
Ultraviolate filters remove most microbes. They ignore organic compounds, inorganic compounds, and metals.
Carbon filters are good at helping resolve some of the problems associated with taste. They generally are made of activated charcoal and remove organic compounds and chlorine. They ignore bacteria, most inorganic compounds and metals. They will not soften water.
Water softeners are very helpful in preventing hard water and iron stains around your sinks, tubs, and showers and giving you water that feels good in your bath. They will also help preserve your plumbing from corrosive action if your water is very hard. They ignore organic compounds, and many inorganic compounds. Bacteria may or may not be eliminated by the high salt content in the exchange unit.
Most softeners work on a sodium replacement principal. In other words, they replace the calcium and magnesium in the water (the hardness element) with sodium. The more calcium and magnesium your raw water contains, the more sodium the softener will add back into your water. You should be aware that drinking softened water could add significant amounts of sodium to your diet.
Most water softener companies will by-pass the kitchen sink and ice-makers and leave those areas hooked to the original raw water.
Reverse Osmosis or "RO" provides a good product. Most units can effectively removemost metals and most inorganic compounds by using a system of special membranes through which the water is moved using pressure differentials. RO units alone will ignore microbes and organic compounds. Usually the system will contain an organic filter and a UV sterilization unit to compensate. The systems are somewhat expensive, ranging in price from $700 to several thousands of dollars. They also require some maintenance by the homeowner or company representative involving changing out the filters.
It is very expensive to treat all of the water to be used in a home or business with RO, so usually a single tap is provided with a small 2 to 4 gallon reservoir under the sink. Homes that desire or need all of the water in a home treated will usually opt for a combination of a water softener and an RO unit.
