There are a number of viable options for improving the quality of drinking water in your home and office. If you are concerned primarily about flavor, consider one of the relatively inexpensive carbon-filter systems (carafes, faucet-mounted filters, countertop filters or in-line undersink filters). If contaminant removal is your primary objective, the most practical and efficient choice is an under-counter reverse osmosis (RO) system. Although distillation systems produce the highest quality of drinking water, their high energy consumption makes them rather impractical.

With RO you also bypass the environmental and carbon-footprint issues associated with plastic bottle usage, transportation, and recycling. Forty percent or more of all bottled water, both in personal-sized bottles or delivered in bulk to your home, is municipal water processed by reverse osmosis.

When selecting a reverse-osmosis system, look for certification by the National Sanitation Foundation International (www.nsf.org) to ensure materials quality, system performance and contaminant reduction. You should be aware that the NSF logo may only apply to a single component part of the unit. It is best to verify certification for the specific unit you are considering on the NSF website under Drinking Water Treatment Units.

The website also serves as a useful guide for what RO systems will and will not remove. They will remove a variety of ions and metals as well as some bacterial contaminants (cysts), but not coliform bacteria. RO systems will remove arsenic V but not the more toxic arsenic III. RO is well documented in the literature and in post-treatment testing to be effective in removing uranium, but NSF does not certify for uranium reduction. With complex well chemistry, RO is commonly used in tandem with other systems to set up a series of barriers for contaminant removal.

One criticism of reverse osmosis-filtered water is that it is stripped of essential minerals. However, most consumers do not depend on water for their nutritional needs but elect to take vitamin supplements or re-mineralize their RO water. Savvy water-treatment companies use a crushed limestone (calcite) post-RO filter to impart a pleasant taste to the water. Parents sometimes express concerns that RO removes the fluoride that is added to municipal water for dental health purposes. This is true, but water fluoridation in general is a controversial issue and today most children under professional dental care receive whole-mouth fluoride treatments.

The most valid criticism of RO is that up to five gallons of water are rejected for every gallon of purified water produced. Actually, many inexpensive, non-certified ROs have much higher rejection rates, are extremely wasteful and still do not deliver verifiable contaminant reduction, which is the primary reason for using reverse osmosis. While reject water is routed to the drain, it is not "lost" but re-enters the hydrologic cycle. In many cases, the RO reject water may be collected and redirected for irrigation purposes.

Stephen Wiman has a background in earth science (Ph.D. in geology) and is the owner of Good Water Company in Santa Fe. He may be reached at 505-471-9036 and skwiman@goodwatercompany.com.

Originally published 10/7/2007 in Santa Fe New Mexican's Real Estate Guide p117