Here are some issues to be aware of with the filter elements on the market today:

• Cartridge Filters – These commonly use Granular Activated Carbon (GAC) – While this type of filter media will remove chlorine from your water, biofilm will form on the surface of the carbon granule and bacteria will grow. Silver can be impregnated into the carbon, which will inhibit bacteria, but not eliminate it. Having your water chilled, as in a pitcher or refrigerator filter, along with the frequent filter changes suggested by the manufacturer, will minimize the risk, but not eliminate it. 

• Ion Exchange Resin – These resin beads are used in cartridge filters to remove toxic metals such as aluminum, selenium, lead, and more. While ion exchange resins are a staple of the water purification industry, they have some important caveats. Ion exchange resins are not contaminant specific, so while it may remove the desired harmful pollutant, it will also remove a lot of non-harmful contaminants. Much of the capacity of the filter you pay for likely will be used, eliminating harmless contaminants. More importantly, ion exchange resin never exhausts. As water is passed through it, contaminants are constantly being held by the resin, while others are given off. If you pass too many gallons through the filter, it attracts new contaminants and gives off some of what it originally held, including the harmful contaminant. There is no practical instrumentation to tell the consumer exactly when to change this type of filter.

• Water Softeners - Softeners use ion exchange resin, and with regular salt regeneration, swap hardness contaminants, namely calcium and magnesium, for sodium to produce so-called “soft” water. These systems eliminate scale build-up, soap scum/rings, and help detergents work much better. Because a softener exchanges 2 parts of sodium for every part of calcium, in areas with high hardness, a softener can create excessive sodium levels for those with health conditions.

• Ultraviolet Light Systems – Ultraviolet light is believed by many to kill bacteria, but it doesn't. UV attacks the DNA and mitochondria portion of the bacteria, preventing it from duplicating and growing. While this effectively does inhibit growth and reduces its ability to impact humans, it also leaves immobile, deactivated bacteria in your water. Once deactivated, bacteria become fragile -- and under the flow and pressure of your pipes, will break up. Bacterial fragments contain protein-rich particles, some of which are called endotoxins that, in some individuals, can cause extreme illness and fever. This material is generally referred to as pyrogenic contamination. On the positive side, the UV process has some advantages over chemicals like chlorine, which is known to create disinfection by-products like trihalomethanes, which are proven to be carcinogenic.

However, one of the better approaches is to consider a whole-home system that combines many or all of the elements above along with Reverse Osmosis. Reverse osmosis is a particular type of filtration that uses a semi-permeable, thin membrane with pores small enough to pass pure water through while rejecting larger molecules such as dissolved salts and bacteria.

Water is unstable. The cleaner it gets, the more unstable and unpredictable it becomes. Remove chlorine, and your house will grow bacteria. Remove metal contaminants, and your water becomes corrosive, pulling copper out of your pipes.

Realize that great-tasting water doesn't equal safe water. The most important thing to remember is that the very moment we filter water, we alter its chemical and physical behaviors.