Conductivity is a measure of the ability of water to pass an electrical current. It is an easy and inexpensive method of detecting the presence of impurities in the water supply. Water containing impurities tend to have a higher conductivity. 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. Conductivity is also affected by temperature: the warmer the water, the higher the conductivity. For this reason, conductivity is reported as conductivity at 25 degrees Celsius (25 C).
Sources of impurity: The basic unit of measurement of conductivity is the mho or siemens. Conductivity is measured in micromhos per centimeter (µmhos/cm) or microsiemens per centimeter (µs/cm). Distilled water has a conductivity in the range of 0.5 to 3 µmhos/cm. The conductivity of rivers in the United States generally ranges from 50 to 1500 µmhos/cm. Studies of inland fresh waters indicate that streams supporting good mixed fisheries have a range between 150 and 500 µhos/cm. Conductivity outside this range could indicate that the water is not suitable for certain species of fish or macroinvertebrates. Industrial waters can range as high as 10,000 µmhos/cm.
Additional notes from Canadian government: CANADA Conductivity – is a measure of the ability of an aqueous solution to carry an electric current. It is an easy and inexpensive method of detecting the presence of impurities in the water supply. Water containing impurities tend to have a higher conductivity. Impurities tend to be harmless.
Maine Maximum Exposure Guideline limit:
USA Primary Drinking Water Standard limit:
USA Secondary Drinking Water Standard limit:
Canada Health standard limit:
Canada Aesthetic standard limit:
USA daily recommended allowance: