1. Conductivity is a measure of the ability of water to pass an electrical current. In the Pacific Northwest conductivity can give indications that there may be salt in the water. Conductivity in water is affected by the presence of inorganic dissolved solids such as chloride, nitrate, sulfate, and phosphate anions (ions that carry a negative charge) or sodium, magnesium, calcium, iron, and aluminum cations (ions that carry a positive charge). Organic compounds like oil, phenol, alcohol, and sugar do not conduct electrical current very well and therefore have a low conductivity when in water.

2. The pH value is a measure of intensity of alkali or acid contained in the water. Absolutely pure water has a pH value of 7.0. In Colorado, the pH of well water normally is between 6.5 and 8.5. Water with pH lower than 5 may cause problems due to corrosion because many metals become more soluble in low-pH waters. A pH value higher than 8.5 indicates that a significant amount of sodium bicarbonate may be present in the water.
3. Calcium and magnesium cause water hardness and result from limestone-type materials in underground soil layers. Separate values are of minor concern but they are combined for calculating hardness. Hardness is the soap-consuming capacity of water; that is, the more soap required to produce lather, the harder the water. Hard water also causes greasy rings on bathtubs, film on dishes or hair after washing, and poor laundry results. Problems caused by hard water in bathing or washing can be overcome by the use of synthetic detergents or packaged softening compounds. The hardness of water may be removed by a water softening unit containing exchange resins. This will result in the exchange of calcium and magnesium (Ca and Mg) by sodium so it may be a concern to people on a low-sodium diet for medical reasons. Do not use softened water for gardens, lawns or plants. Hardness is reported as calcium carbonate in milligrams per liter (mg/l).
4. Sodium may indicate salt water intrusion.  Sodium can be reduced or removed by expensive treatment systems, but when Ca and Mg are removed from water by passing through a water softener, sodium replaces it.
5. Potassium is an essential nutritional element, but its concentration in most drinking water is trivial and quantities seldom reach 10 mg/l.
6. Carbonates and bicarbonates are the major contributors to the “totalalkalinity” that may be determined in a routine water test. The alkalinity of a water sample is a measure of its ability to neutralize acids. Naturally occurring levels of total alkalinity up to 400 mg/l as CaCO3 are not a health hazard. Low alkalinity is associated with low pH values and may indicate potential for problems due to corrosion of metal in plumbing systems.
7. Chloride concentrations in drinking water may indicate salt water intrusion.  Most people will detect a salty taste in water containing more than 250 mg/l of chloride. Expensive treatment methods are needed to remove chloride from water.
8. Sulfate content in excess of 250 to 500 ppm (mg/l) may give water a bitter taste and have a laxative effect on people not adapted to the water. Expensive treatment methods are necessary to remove or reduce sulfate in a private water system.
9. Nitrate in excess of 45 mg/l (or in excess of 10 mg/l if reported as nitrate-nitrogen) is of health significance to pregnant women and infants under 6 months. Do not use high nitrate-water in infant formulas or other infant foods. Considerably higher nitrate content apparently is tolerated by most adults. Nitrate can be removed from private water supplies, but the equipment is expensive and not commonly used.
10. Total dissolved solids, also called “total mineral content” or “total residue,” is the total amount of material remaining after evaporation of the water. Values of less than 500 ppm (mg/l) are satisfactory and up to 1,000 ppm (mg/l) can be tolerated with little effect. Fluoride is important in the development of teeth in infants and youth. The optimum fluoride content to assist in the control of tooth decay is 0.9 to 1.5 ppm (mg/l). Excessive amounts are rarely found in Colorado waters, but a concentration over 3.0 ppm (mg/l) may cause darkening of the tooth enamel and other undesirable effects.
11. Iron and manganese are nuisance chemicals that cause troublesome stains and deposits on light-colored clothes and plumbing fixtures. Iron causes yellow, red or reddish-brown stains and deposits, while manganese stains and deposits are gray or black. Excessive amounts also may cause dark discoloration in some food and beverages and cause an unpleasant taste. Iron and manganese can be removed or reduced in a softener equipped with special resins or by small treatment systems involving aeration, filtration and chlorination.
12. Copper and zinc will cause an undesirable taste if concentrations are above the recommended limits. A water softening system should significantly lower the levels of these elements.
13. Arsenic, selenium, barium, cadmium, lead and mercury are potentially toxic elements. Fortunately, these elements rarely exceed the mandatory limits in most Colorado well water. If high concentrations are found, it is necessary to remove these elements using expensive treatment methods, such as distillation or reverse-osmosis. Lead contamination in drinking water can come from lead pipes and lead-based solder pipe joints.
14. Aluminum, ammonium, phosphorus, nickel and molybdenum are additional constituents that can be determined by the laboratory. Although no limits are established for these parameters, pollution of some sort is indicated if significant concentrations are detected in a water sample.

Taste and odor problems are difficult to solve. Some inorganic compounds may impart detectable tastes without odor. Hydrogen sulfide (rotten egg smell), when present, will impart an undesirable odor and taste. Generally, undesirable tastes may be caused by any of numerous organic compounds. These may be present naturally in the water or due to sewage or other surface contamination sources. They can impart disagreeable taste and odor in minute concentrations (a few parts per billion or a few milligrams per kiloliter) and specialized chemical tests are needed to detect such small levels. Turbidity in drinking water is caused by suspended sediments from erosion and runoff discharges. The maximum contaminant level in drinking is 1 to 5 turbidity units.

Water Treatment Systems

Some water constituents can be removed or reduced by ion-exchange resins, distillation, reverse osmosis or a combination of these methods. Other treatment processes might involve aeration or chemical oxidation followed by filtration. Organics can be removed by filtration through charcoal, but this may not be an effective method for removing inorganic contaminants. Treatment methods are specific to the type of chemical problems and generally are quite costly. For additional information on water quality or treatment systems, refer to the fact sheets listed below or call the EPA Safe Drinking Water Hotline, (800) 426-4791.