Understanding Water Filtration

The quality of our source water has degraded in the last 40 years. While municipalities are working harder than ever to maintain quality, much can still happen to water after it leaves a treatment facility. Consequently, "consumers need to be more aware of it and take more responsibility for things within their home to make sure they really are covered," says Pauli Undesser, executive director of the Water Quality Association. Fortunately, an array of treatment solutions is available to protect against potential problems.

Water treatment products fall into one of two categories: point-of-use and point-of-entry. The former conditions water intended for consumption and includes everything from countertop pitchers to faucet attachments and under-the-sink systems. Point-of-entry devices are whole-house systems that remove "non-health-related" contaminants, which can stain or leave deposits on plumbing, and thus "help with maintaining your property or investment," Undesser says.

Several methods exist for treating water

Ion exchange. Ion exchange water softeners are one of the most common, as 85 percent of the country's water is considered hard. These point-of-entry products soften by eliminating calcium and magnesium, which can accumulate on plumbing and have an impact on appliances. Inside the device, resin beads capture calcium and magnesium ions as water flows through. When the beads become saturated, a brine tank rinses them with salt, readying them for reuse.

Activated carbon. Another popular method uses activated carbon to filter out a variety of harmful chemicals, as well as those that affect taste and odor. These include chlorine, which is typically used by utilities as a disinfectant, and its byproducts, which can be hazardous. Some filters incorporate other media to target heavy metals and other contaminants. Activated carbon filters work by adsorption, but once saturated, need to be replaced.

Several methods exist for treating water

Reverse-osmosis. Reverse-osmosis (RO) systems treat water by forcing it through a semi-permeable membrane, leaving impurities and pollutants to be flushed down the drain. They typically comprise pre-filters for removing sediment and chlorine; the RO membrane; post-filters, which eliminate any lingering taste or odor issues; and a storage tank. The water produced is high-purity but limited in quantity (3 to 10 gallons a day), making RO ideal for point-of-use applications, although whole-house units are available. RO systems cost more than their carbon counterparts, and both filters and membrane require replacement.

Distillation. Also producing small quantities, distillation is one of the oldest purification methods, but it has fallen out of favor. It heats the water until it vaporizes and then feeds it into a condenser that converts it back into liquid form. A vent is included for discharging gases, and an activated carbon filter removes chemicals, such as chlorine, that are unaffected by distillation. Distillers need periodic maintenance and are slow and inefficient.

Reverse Osmosis. Distillation. Water Filtration.

Ultraviolet light. According to Undesser, a popular method used in Canada, but not in the U.S., disinfects water by exposing it to ultraviolet (UV) light. Available for point-of-use and point-of-entry applications, UV light products kill microbes without chemicals, but their effectiveness depends on the intensity of the light, the length of exposure and water turbidity. Moreover, gases, heavy metals and particulates are not affected, which is why some systems include an activated carbon filter.

Ozone. Another chemical-free purification system uses ozone converted from oxygen in the surrounding air by way of a generator. When it mixes with water, the ozone quickly kills microorganisms and breaks down iron, sulfur and manganese through oxidization. It then decomposes, leaving no taste or odor. Ozone purification does not, however, remove chemical contaminants and therefore is often combined with other filtration methods.

Ultraviolet Light. Ozone. Water Filtration.

Other technologies are emerging that, with wider use and research, may prove more effective. Until then, remodeling and design professionals can benefit by first understanding the water quality in the areas where you work and the treatment options available.