* Second of two articles

The occasional sensational news story about a drinking water problem somewhere in the United States could lead you to think that contaminated water is common in this country. It's not. American water utilities generally produce safe drinking water.

But the water can become contaminated between the time it leaves the treatment plant and the time it comes out of your faucet. Or your household may be one of an increasing number that gets its drinking water from a private well that could be contaminated. Water testing can determine which contaminants might be a concern for you.

However, water testing is only the first step. Then you have to get the correct filter. Different types of filters take out different contaminants, and there is no "one size fits all" solution.

The least expensive and most widely available filters are the activated carbon type, also known as activated charcoal filters. These can be cartridges in a simple pour-through pitcher, a device that attaches to your kitchen faucet, a device integrated into the faucet (aesthetically less awkward but much more expensive), or a larger unit under the sink with its own faucet. This last type may require professional installation, but it may also remove more contaminants than the smaller ones.

The most basic carbon filters remove chlorine taste and odor as well as particulates suspended in the water. The more sophisticated ones have added media that can remove an impressive number of substances, but you have to check carefully to make sure the ones removed are the ones that concern you. For example, the box for Culligan's UnderSink Charcoal Filtration System Model SY-2650 lists 55 substances it removes, but arsenic is not on the list. An activated carbon filter can remove arsenic, but only if a specific medium for this has been added.

A less common and more expensive type of drinking water filter is a reverse osmosis system. It also goes under the sink, may require professional installation, and has its own faucet. In reverse osmosis, water is forced through a membrane that removes most contaminants, but it is always sold with pre- and post-carbon filters. The two methods remove more than either alone.

Reverse osmosis systems have their downside. They waste a lot of water -- for every gallon they purify, two to five gallons are discarded.

The most common consumer complaint, though, is speed. Most models take four to 12 hours to produce two to three gallons of water, which is stored in a tank under the sink. As the average family of four consumes only about two gallons of drinking water a day, this can be workable for regular use -- every night the system can replenish itself. If you entertain frequently, though, it's not a great solution. However, GE Water Technology's Marlin reverse osmosis system has no tank and delivers a half-gallon of water a minute. The system will be available through independent water treatment dealers Aug. 1, but it's pricey -- about $700 to $1,000, compared with a conventional reverse osmosis system at about $200 to $350.

Another new type of reverse osmosis filtration system is one that, in combination with carbon filters, removes bacteria and viruses. The carbon blocks are made by KX Industries, an Orange, Conn., firm that supplies the carbon filter components for most U.S. filtration manufacturers. Until now, no carbon filter maker has claimed to remove bacteria and viruses, and there was no test to certify such a claim. KX, working with the Environmental Protection Agency and the California Department of Health Services, designed a certification test that was administered by a California-certified microbiological lab.

In August, KX's Matrikx filter will be available at Costco in the Watts Premier Reverse Osmosis System. In October, KX will market a stand-alone carbon filtration system, the Matrikx Microbiological Barrier, under its own Matrikx brand.

KX's Matrikx filter will not greatly benefit homeowners with city water, but such a system could be a real boon to homeowners whose water source is a private well and who also live near a septic field.

The real beneficiaries, however, will be the 3 billion people who live in Third World countries without access to safe drinking water. For that market, KX is manufacturing a World Filter, which will differ from the one sold in the United States. The World Filter is intended to help people who carry water from a central village source to their homes, as well as those whose municipal water is contaminated.

Another drinking water filtration possibility is a distiller. I tried out a Kenmore Model 34480, which took about five hours to distill three quarts.

In this type of system, water is placed in one chamber and boiled to produce steam, which is then passed through a charcoal filter and condensed back into water in a separate chamber. The distilling process is extremely effective at removing most contaminants, and I found the taste of the water pleasant.

The EPA and the National Sanitation Foundation, an organization that certifies water filtration devices, caution that some contaminants, such as volatile organic chemicals, readily convert into gas. These may be carried over into the distillation chamber with the purified water. If you have well water and you discover, for example, that it contains MTBE, a gasoline additive that can leak out of underground storage tanks and get into ground water, a distiller would not be your best option.

Once you have decided on a filtration system, how sure can you be that it removes what the manufacturer claims? You should look for a certification from the National Sanitation Foundation, Underwriters Laboratory or the Gold Seal of the Water Quality Association.

But fraudulent claims have not been an issue in the industry. Richard P. Maas, an environmental sciences professor at the University of North Carolina at Ashville, who has tested dozens of water filters over the last 17 years, has found no case in which a manufacturer claimed to remove something and didn't.

The main issue with filters is not false claims but bad homeowner maintenance, Maas said. A carbon filter mechanism needs to be replaced every few months, depending on how many gallons of water you use a day. Some filtration systems have an indicator that slowly changes color to indicate replacement is required. But most do not, and most city water does not contain enough particulates to clog the mechanism, which would also signal that the filter should be replaced. You just have to mark your calendar when you install a new filter and follow the manufacturer's recommendations for replacement, Maas said.

With a typical municipal water supply, a reverse osmosis membrane should be replaced every three to five years, and the carbon filter components of the mechanism should be replaced every six months, said Sam Karge of GE Water Technologies.

Another option, though the most expensive over time, is bottled water. Your local grocery store sells a large selection, nearly all of them bearing labels with pictures of snow-covered mountains or some other distant and presumably pristine water source.

But much of the water, including that of some of the top-selling brands, is simply glorified tap water. In its August 2000 report, Consumer Reports found that Pepsi's Aquafina purified drinking water "originates from 16 sources -- mainly municipal water supplies" and Coca-Cola's Desani to be "purified from municipal sources."

Katherine Salant can be contacted at www.katherinesalant.com.

(c) 2004, Katherine Salant

Distributed by Inman News Features

Filters can be as simple as this pitcher cartridge or as complicated as distillers.