COLUMBIA, Mo. - Consumers should look closely at their needs before investing in a water filtration system, said a University of Missouri Extension water quality specialist.

"Many consumers spend money for unneeded and costly filtration systems that offer little real health benefits," said Bob Broz.

Public water supplies in this country provide some of the safest and cleanest water in the world at very low cost, he said.

Filter systems vary in the amount and type of impurities they can remove from water. When considering a filtration system, consumers should make sure it matches their needs.

If you simply want to improve the taste or odor of tap water by removing chlorine and sediment, a basic carbon filter attached to the faucet may suffice. If your household uses low-quality well water, you might need a whole-house system, which can be expensive.

Customers of year-round community water systems who have concerns about water quality may request from their utility a consumer confidence report detailing the levels of any EPA-regulated contaminants.

If you are on a private water supply system, several laboratories provide services to determine if a well meets the basic requirements for safe drinking water. In most counties, the health department can test samples from private wells for bacteria at minimal cost.

When comparing prices, consumers should add the cost of replacement filters to the retail price of the product. Operating costs of top filter systems may range from 4 to 25 cents per gallon, Broz said.

Whole-house water treatments, such as reverse osmosis systems, can be very expensive to operate if filtering is not limited to water for cooking and drinking. "You lose three gallons for each gallon you get out of a reverse osmosis system," he said. Add electricity and maintenance costs and you could end up spending $25 or more per day for your water.

Broz warns that consumers should not try to save money by postponing filter replacement. "Leaving in filters beyond the manufacturer's recommendation can prove inefficient and even harmful by providing an environment for bacterial growth," he said.

Before you purchase a filtration system, make sure it has been tested and certified at a lab run by an independent nonprofit entity such as NSF International or Underwriters Laboratory.