There are about 2500 drinking water treatment systems of one sort or another on the market in the United States for home use. Some are as simple as filters you place on top of a pitcher, and pour water through. Some are as complicated as whole-house systems coupled with a water-softening system, which cost thousands of dollars.
A good salesman can make his product look like the clear choice that only an idiot would turn down for a different product, and it's no different with drinking water treatment systems. There is hype on all sides. By the end of this article, you'll know what you need to know about home water purification systems.
There are two types of systems widely sold in the United States:
· Reverse Osmosis A reverse osmosis system forces water through a membrane, which is essentially a filter, which has pores so small that the water molecules can just barely get through. Anything larger than a water molecule, like many dissolved solids, heavy metals like lead, and many chemicals, can't get through.
· Activated Carbon or "Solid Block Activated Carbon" (SBAC) An SBAC unit filters out contaminants via two processes-physical removal, where contaminants get stuck in the nooks and crannies and pores of a block of carbon, and adsorption, where contaminants are attracted and held to the surface of the carbon particles.
Advantages and Disadvantages:
· Advantages of Reverse Osmosis
1. Significantly reduces salt and most other inorganic material, and some organic compounds.
2. Parasites and viruses are usually removed by a properly-functioning unit.
3. When coupled with a high-quality activated carbon filter to capture the volatile organic compounds (VOCs) that get through the reverse osmosis process, the treated water is essentially free of contaminants.
· Disadvantages of Reverse Osmosis
1. Point-of-use units at each faucet can make just a few gallons a day, so they require a storage tank, which takes up room, and requires maintenance.
2. Reverse osmosis wastes three to ten gallons of water for every gallon of treated water produced.
3. More maintenance is required to change filters and membranes and to clean the storage tank.
4. The efficiency of the membrane can degrade due to attack by some contaminants, and the slightest tear or other damage, which is hard to detect, can allow untreated water to flow through the system.
5. Because of their complexity, they are typically more expensive to install and to operate. Compared with the leading activated charcoal unit, they're usually about 2 ½ to 3 ½ times as expensive to operate.
· Advantages of Solid Block Activated Carbon Drinking Water Treatment Systems
1. Provide a very small pore size and a huge surface area to attract and trap bacteria and cysts; most chemicals, including VOCs; and pharmaceuticals.
2. Don't waste water like reverse osmosis systems.
3. Lower initial cost and lower operating costs.
4. Calcium, Potassium, Magnesium are not removed. Water tastes better, and provides some small amount of useful minerals to the body.
· Disadvantages of Solid Block Activated Carbon Drinking Water Systems
1. Do not reduce levels of dissolved salts such as nitrates, fluoride, arsenic and cadmium. These contaminants are not usually a problem except in heavily agricultural areas with poor water treatment facilities, but if they are, a reverse osmosis system would be preferable.
Bottom Line Unless the substances in the preceding paragraph are an issue, activated carbon drinking water treatment systems seem preferable. They don't waste water, they're less expensive to operate, and they're simpler and less prone to maintenance/degradation issues.