Still, about 19 million Americans -- residents of every state (and many from major cities) -- become sick each year because of microorganisms in their drinking water. Indeed, more than 20 percent of U.S. water systems are in violation of the Safe Drinking Water Act, according to an analysis of data recently published.

Testing the waters
Before shopping for filtration systems or deciding your family can drink directly from the tap, the smartest thing you can do is to learn what's in your water.

If your water is publicly supplied, a good first step is to review the quality report your local utility is obliged to provide by law. The annual Consumer Confidence Report includes a list of contaminants detected in a local system and details whether levels exceed safe drinking standards set by the Environmental Protection Agency. To find your local report, see link below.

Deep analysis
The CCR program has a few limitations, including the fact that independent water sources such as private wells are not monitored. Critics have noted that the list of contaminants in the Safe Drinking Water Act needs updating. Crucially, water quality can differ from house to house even for residences on the same water system. That's because water can be contaminated in the lengths of pipe between your street connection and your spigot. Old pipes on a property, for instance, pose a risk of lead contamination or leakage. As a source inside the EPA told The Practical Guide, low pressure can result in contaminants being drawn into a leaky pipe from surrounding soil.

"There may be solvents, pesticides, or other long-life contaminants in the ground that can travel into drinking water," said the source. "It depends on how the surrounding property has been used in the past, so sometimes it's worth researching some local history. There are also contamination risks associated with local conditions, such as a neighbor's sewage."

Because water quality is unique to every home, there's really just one way to get an accurate assessment of your tap water: Have a sample from your faucet analyzed by a laboratory. The lab will send you a kit, plus directions, for collecting and sending the sample. See below for a lab index.

What is your filter filtering?
Here's the dirty little secret on water filters and treatment systems: There is no catch-all solution. Let's take a brief look at the leading methods and the efficacy of each.

Activated carbon filters. Effective in clearing odors and bad tastes. Can reduce (not entirely remove) lead and copper. Some units remove pesticides, cleaning solvents and chlorination byproducts. Does not remove nitrates or dissolved minerals. Bacteria can colonize inside a carbon filter; though generally harmless, bacteria can cause disease among the very young, the elderly, or those with pre-existing health issues. Many pitchers, faucet mounts and countertop filters incorporate activated carbon.

Ion exchange: Widely used for water softening because it removes the "hard" minerals calcium and magnesium. Some models remove radium and barium. Units with activated alumina also reduce flouride. These filters can get plugged up if there's a lot of oxidized iron or iron bacteria in the water. Ion exchange filters have to be regenerated periodically with salt. Several pitchers and faucet-mounted models use the ion exchange method (often in combination with activated carbon).

Reverse osmosis: Slow, oversized and wasteful of water -- but more effective against a wider range of contaminants than other filtration methods. Removes nitrates, sodium, some pesticides, chloroform and petrochemicals; also, the only method certified to remove arsenic. Good against foul tastes and smells. Does not remove all inorganic and organic contaminants. Typically installed under a sink, these units use household pressure to screen impurities as water passes through a membrane.

Distillation: Very effective against impurities, including nitrates, organic compounds, bacteria, heavy metals and radionucleides. Produces sodium-free water. Won't remove some pesticides and solvents. Distillation simply involves boiling water and then condensing steam. The units are typically countertop models that are plugged into an outlet; not especially practical for large, frequent quantities.

If all of this sends you directly to the market to purchase water, you'll certainly find plenty to choose from. Be aware, though, that bottled waters are not immune to contamination either. In the long run, nothing beats the simplicity and affordability of a clean glassful at your own tap. You just have to know how to get it flowing.