Water Filters

In our last issue, we addressed some potential problems encountered with tap water. In this issue, the topic of water filters as a method of improving the safety of your water is discussed.

Annual sales of home water filtering units, and other water treatment devices, is approaching four billion dollars. The first step in buying a water filter is knowing what contaminants are in the water. This was discussed last time. Once you know what (if anything) needs to be filtered, you can use the appropriate device. Unfortunately, there is no single water filter which will solve all your water problems.

Basically, there are four categories of water filters: activated carbon systems, re-verse osmosis systems, ion-exchange resin filters, and distillation units. Each one will filter water of specific contaminants.

Carbon filters, used by the ancient Greeks and Romans, traps contaminants as the water passes through the carbon filter. The newer, solid-carbon-block filters are the most effective for this process (as opposed to granular carbon devices). Reverse osmosis has been used on a large scale, such as for desalination of seawater, in industry. Basically, it’s a more fancy filtration system which includes carbon. Home units generally are more expensive when maintenance is considered. Ion exchange, a simple unit made of a resin, filters only a few contaminants. Distillation, like carbon filtration, is an ancient method of treating water.

The process involves boiling the water to be treated, capturing and cooling the stream, which gives you cleaner water.

Here's a list of the different types of filtration systems and the substances they best eliminate:

Activated Carbon Systems

(using solid-carbon-block filters)

- removes most organic chemicals, such as pesticides and herbicides, chlorine, bacteria, metals (lead, iron, copper) and radon

- won't remove minerals (won't soften water), nitrates, viruses, and radioactive particles

usually improves the taste of the water some carbon filters have silver nitrate to prevent bacterial build-up - this may be effective but may also leak silver

can cost as little as $40 and as much as several thousand dollars or more for the entire system

ideally, the carbon part must be re-placed every 6-12 months to maintain effectiveness, normal water flow.

Reverse Osmosis Systems

- removes toxic metals and radiation

contamination (except radon)

will not remove many organic chemicals or radon

- interferes with normal water flow (by 25-50%), and for every gallon of clean water, 6-8 gallons of water are wasted.

may cost $150 to several thousand dollars

Ion-Exchange Resin Filters

- removes nitrates and nitrites, toxic metals and radiation contamination (except radon)

- will not remove many organic chemicals or radon - cost $200-$500

Distillation Units

-all around best method, as it "filters" more items than any other one device

removes toxic metals and radiation contamination (except radon)

- will not remove all organic chemicals or radon removes minerals (softens the water)

-makes water taste "flat"

-cost from $300 to $3,000

The manufacturer of these filtering devices should provide you with specific information on what contaminants it removes as well as proper use, installation and maintenance costs. Also, it is well worth testing your water again after installing a water filter to be certain it is performing properly.

Most importantly, if your water is contaminated you should attempt to find the source of that problem and correct