Mother Earth Living

Five Home Water Filtration Systems to Consider

Once you know what you need to filter, choose the system that stops those toxins.
By Alli Kingfisher and Kelly Lerner
September/October 2010
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Absorptive media (include carbon filters)

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Filter type
1. Absorptive media (includes carbon filters)

How it works
Solid, porous, highly absorbent material such as charcoal traps liquids, solids, and dissolved or suspended matter

What it removes
■ Foul taste and odor
■ Some cleaning solvents
■ Some pesticides, parasites and radon
■ Heavy metals such as lead, copper and mercury
■ Some types remove chlorination byproducts
■ Some volatile organic chemicals
■ Arsenic and protozoan cysts

■ Does not remove nitrates, bacteria or dissolved minerals
■ Carbon filters must be replaced regularly

Filter type
2. Water softeners (cation exchange)

How it works
Uses sodium (either sodium chloride or potassium chloride) to replace calcium and magnesium ions

What it removes
■ Minerals that cause hardness, such as calcium and magnesium
■ Some types remove radium, barium and nitrates

■ Does not remove bacteria

Filter type
3. Reverse osmosis

How it works
Forces water through a semi-permeable membrane under pressure, leaving contaminants behind (most systems incorporate pre- and post-filters)

What it removes
■ Nitrates, sodium
■ Disease-causing organisms
■ Many dissolved inorganic and organic solids
■ Many heavy metals, such as cadmium, copper, lead and mercury
■ Foul taste, smell or color
■ Arsenic, barium, perchlorate and selenium

■ Does not remove all inorganic and organic contaminants
■ Units use approximately three times as much water as they treat

Filter type
4. Distillation

How it works
Heats water to boiling point and collects the vapor as it condenses, killing disease-causing microbes and leaving most contaminants (particularly heavy metals) behind

What it removes
■ Some bacteria, viruses and parasites
■ Nitrates, sodium, hardness, dissolved solids, most organic compounds and radionuclides
■ Arsenic, barium, fluoride and selenium
■ Heavy metals, such as cadmium, chromium, copper, lead and mercury

■ Does not remove some volatile organic compounds, certain pesticides and volatile solvents
■ Contaminants that easily turn into gases, such as radon, may remain in the water
■ Bacteria may accumulate on coils during inactive periods
■ Water may taste flat

Filter type
5. Ultraviolet Disinfection

How it works
Ultraviolet light kills bacteria and other microorganisms

What it removes
■ Bacteria, parasites and some viruses

■ Only kills microorganisms; does not remove anything from water

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