What is the electrical conductivity of water?

The electrical conductivity of water (EC) is a measure of the ability of water to conduct an electric current. This ability is directly related to the concentration of conductive ions in the water. These conductive ions are formed due to the presence of inorganic substances such as chlorides, alkalis, carbonate compounds, and sulfides, and dissolved salts. Most metals are excellent conductors of electricity due to the large number of free electrons.

Definition of water conductivity

The rate at which water conducts or transfers electricity, heat, or sound is called water conductivity. It is expressed in units of s or k.

Units of measurement for water conductivity:

Difference between Electrical Conductivity and Conductivity:

Electrical conductivity is based on conductivity. Conductivity is the ability of a material to conduct current. The units of measurement for electrical conductivity (EC) are (S/cm), (mS/cm), (μS/cm), (dS/m). For example, distilled water has an electrical conductivity of 0.55 μS/cm at 25°C.

Silver has the highest conductivity among metals: 106 x63 S/m

Electrical Resistivity

Electrical resistivity (ρ) is the ability of a material to conduct current and is not focused on resistance. The units we use to measure electrical resistance include cm x ohms. For example, distilled water has a value of 18.16 Mohm.cm at 25°C.

Electrical conductivity of different types of water:

Distilled water 0.05 µS/cm

Drinking water 800 – 200 µS/cm

Sea water 50,000 – 40,000 µS/cm

The Relationship Between Electrical Conductivity and TDS

TDS is a measure of the total solid ions present in a solution. Electrical Conductivity (EC) is actually a measure of the ionic activity of a solution in terms of its current carrying capacity. In dilute solutions, TDS and EC are reasonably comparable.

The TDS of a water sample based on the measured EC value can be calculated using the following equation:

(mg/L TDS) = EC x 0.5 (dS/m or mmho/cm)

or

EC x 1000 x 0.5 (mS/cm)

Distilled Water Conductivity Limit

Unlike other waters, there is no fixed standard or universal "limit" for electrical conductivity (EC) for distilled water. This value is directly influenced by the end use of the water. Ideal distilled water is free of any conductive ions and therefore has zero electrical conductivity. However, in real-world conditions, contact with the atmosphere dissolves minute amounts of carbon dioxide (CO₂) and results in a very low electrical conductivity (typically in the range of 0.5 to 5 microsiemens/cm).

For many general and laboratory applications, water with an electrical conductivity of less than 2 µS/cm at 25°C is considered to be of acceptable distilled quality. However, for very sensitive processes such as semiconductor manufacturing or precise chemical experiments, higher purity water (such as deionized or ultrapure water) is required, resulting in an electrical conductivity much closer to zero.

*The laboratories of Abrizan Industrial Research Company located in Fars Science and Technology Park are capable of measuring a variety of water parameters, including Electrical Conductivity (EC), using advanced devices and equipment.