Domestic water is generally supplied to homes through private wells or public water companies. Water supplied by public water companies is usually safe to drink and does not pose a health risk. The quality of the water supplied by these companies is periodically checked because it must comply with rigid standards set by the U.S. EPA. Nevertheless, the EPA has indicated that some 40 million people have been using drinking water containing potentially hazardous levels of lead. The problem does not originate with the water supply but with distribution piping, solder used at the pipe fittings, and fixtures in the house. In some older homes, the inlet water pipe is made of lead; the solder used on pipe fittings in homes built before 1988 contained lead; and lead is contained in the metal alloy used in the manufacture of many faucets.
The most important factor causing a high concentration of lead in water is the contact time between the water and the lead. Water that is slightly acidic or soft (water that makes soapsuds easily) is corrosive and reacts with lead. When the water stands in pipes or faucets that contain lead for several hours without use, there is a potential for lead to leach, or dissolve, into the water. Also, hot water dissolves lead more quickly than cold water.
Dissolved lead in water has no odor and cannot be seen or tasted. Testing by an approved laboratory is the only way to determine if the drinking water has high levels of dissolved lead. The test is generally conducted in two parts, A “first draw” sample is collected- water that has been sitting in the pipes overnight or at least four hours. Then a “fully purged” sample is collected; the water is turned on and allowed to flow for at least one full minute before a sample is collected. According to preliminary studies at the University of North Carolina, about 30 percent of homes have a high lead concentration in the first draw, but purging corrects the problem more than 90 percent of the time. The current federal standards limit the amount of lead in water to 15 parts per billion (ppb), which is equivalent to 0.015 milligrams per liter (mg/l).
Another domestic water problem is excessive sodium. This condition is the result of using a water softener in the water supply. The softener replaces the calcium in the water with sodium. When the sodium concentration in the water is greater than 28 mg/l, people with high blood pressure and those with low-salt diets should be warned. When using a water softener, the sodium content is usually 100 mg/l or more. The problem can be corrected by having the pipe that supplies water to the kitchen sink bypass the water softener. All drinking and cooking water should then be taken only from the kitchen sink.
In addition to the possibility of high concentrations of lead and sodium, domestic water supplied by a private well can be contaminated by harmful bacteria resulting from faulty septic tanks, chemicals from a toxic spill that occurred years before, leaking underground storage tanks, or pesticides and fertilizers. The only way to tell whether the water is potable is to have it tested. The tests for pesticides and other chemicals are more complex and costly than the routine tests for bacteria or minerals. If you are concerned about pesticide and chemical contamination of your well, first contact your county officials and find out whether contamination problems have been reported in the area. As a precautionary measure, the water from a private well should be analyzed once a year for coliform bacteria to ensure that it is potable.