Do water filters work?
You’ve read about the outbreaks of waterborne illnesses recently in places like Milwaukee, Las Vegas, New York City and Washington. You’ve been concerned that traces of lead may be lurking in your pipes. You’re concerned about the intake of chlorine. You want to make sure your water is bacteria free. So just to be safe, you use different types of water filters every day. Trouble is, you may not be any better protected. In fact, the water you drink may be dirtier than it was before. How can this be true?
The U.S. is blessed with one of the best water-supply systems in the world. Yet half of all Americans worry about getting sick from tap water contaminants, according to a survey by the Water Quality Association. As if to underscore the point, the Environmental Protection Agency has ordered the nation’s 300 largest municipal water suppliers to begin testing for the cryptosporidium parasite, which poses a risk for people with weakened immune systems.
No wonder Americans continue to purchase billions of dollars worth of water-treatment systems every year. According to Baytel Associates, a market-research firm in San Francisco, 12% of U.S. households treated their water in 1995, 39% of homes in 2003, and it is expected to jump to 60-70% in the next 10 years.
But do these home treatment systems work? That depends, experts say, on what you want them to do. “Not every product does everything,” says Nancy Culotta of Michigan’s NSF International, an Ann Arbor-based industry watchdog group. Some filtering systems, she notes, improve the water’s taste and odor by getting rid of inorganic chemicals like sulfur or chlorine. Others do a creditable job of removing lead but aren’t designed to purify water tainted by bacteria or other pathogens. And many systems need to have their filters frequently replaced, or owners will wind up running their tap water through the high-tech equivalent of a dirty sponge.
Hundreds of products are on the market, but the technologies they use fall into a few basic categories:
ACTIVATED-CARBON FILTRATION. These systems are the most popular and the most effective in reducing contaminants like chlorine and sediment. Filters made of carbon in solid block form, as opposed to granules, are also highly effective in reducing lead. Systems range from pour-through carafes to water bottle filters to portable water filters to water filters that are mounted on faucets, on countertops or under the sink. Cost: $5 to $80.
REVERSE OSMOSIS. These compact units force pressurized water across semipermeable membranes. Lead, arsenic and even some pathogens like Giardia are flushed out of the system–along with 50% to 90% of the water. The purified water that’s left behind is passed through yet another filter and stored in a pressurized tank. This option is very expensive and requires a lot of plumbing and space for tanks. There are some under-the-sink models that can cost well over $1,000.
DISTILLATION. These water filters boil water and turn it into vapor, removing most inorganic contaminants like lead and killing any pathogens. The steam is then recondensed into water. However, distillation is not useful for removing volatile chemicals like benzene. The most common complaint is the taste of the water. Because of the process used, distilled water has a very “Flat and Old” taste. Though it’s clean, it many time does not taste clean. Prices start at more than $250.
