Conductivity, in the context of water, refers to the water’s ability to conduct an electric current. This property is directly related to the presence of ions—charged particles—in the water. The more ions present, the higher the conductivity. In simple terms, conductivity is a key indicator of water quality and is used across various industries, including environmental monitoring, wastewater treatment, hydroponics, aquariums, and even in laboratories.

The concept of electrical conductivity in water is based on the movement of these charged particles (ions) when an electric field is applied. Pure water, which has very few ions, is a poor conductor. However, when substances such as salts, acids, or bases dissolve in water, they dissociate into positive and negative ions, increasing the water’s ability to conduct electricity.

Conductivity is usually measured in microsiemens per centimeter (µS/cm) or millisiemens per centimeter (mS/cm), with 1 mS/cm being equal to 1000 µS/cm. It is a quick, non-destructive, and cost-effective method of assessing the ionic content of water, making it a popular parameter in many scientific and industrial applications.

In this blog post, we’ll explore how to measure conductivity in water, what factors can affect the measurement, typical conductivity values in different water types, and important considerations to keep in mind before taking a reading.

What Will Affect Conductivity Measurement?

Several factors can influence the accuracy and reliability of conductivity measurements. Understanding these factors is essential to ensure that you are getting correct and consistent results.

1. Temperature

Temperature is one of the most significant factors affecting conductivity. As water temperature increases, the mobility of ions also increases, leading to higher conductivity readings. For this reason, conductivity meters often have automatic temperature compensation (ATC) features that adjust the reading to a standard reference temperature, typically 25°C.

2. Ion Concentration and Type

The type and concentration of dissolved ions in the water play a direct role in conductivity. For example, sodium chloride (table salt) will increase conductivity differently than calcium sulfate. Some multivalent ions (like Ca²⁺ or SO₄²⁻) may contribute more significantly to conductivity than monovalent ions (like Na⁺ or Cl⁻).

3. Dissolved Gases

Certain gases, such as carbon dioxide (CO₂), can dissolve in water and form weak acids, which then dissociate into ions. This process can slightly increase the conductivity of the water.

4. Turbidity and Suspended Solids

While pure suspended solids do not directly affect conductivity, turbid water can interfere with electrode-based measurements by coating the sensor or causing erratic readings. It’s best to filter or settle the sample if high turbidity is expected.

5. Electrode Contamination and Fouling

Conductivity sensors can become fouled by organic material, mineral deposits, or biofilms, especially in untreated or natural water sources. This contamination can insulate the electrodes and lead to inaccurate low readings. Regular cleaning and maintenance of the sensor are crucial.

6. Calibration and Instrument Accuracy

Using a poorly calibrated or low-quality conductivity meter can result in incorrect readings. Calibration with standard solutions of known conductivity is necessary to ensure accuracy.

Typical Conductivity Levels

Understanding typical conductivity values for different water types can help you interpret your results and identify potential issues. Here are some general guidelines:

Ultra-pure water: 0.055 µS/cm (resistivity ~18.2 MΩ·cm)

Distilled water: 0.5 – 3 µS/cm

Deionized water: 0.1 – 10 µS/cm

Drinking water: 50 – 800 µS/cm

Groundwater: 100 – 2000 µS/cm

Seawater: 50,000 – 60,000 µS/cm (or 50 – 60 mS/cm)

Wastewater: 700 – 7,000 µS/cm (can be much higher depending on source)

These values can vary based on geographical location, season, and specific water treatment processes. For example, agricultural runoff or industrial discharge can cause sudden spikes in conductivity.

How to Measure Conductivity in Water?

Measuring conductivity in water is a straightforward process, but it requires attention to detail to get accurate results. There are several methods and tools available, ranging from simple handheld meters to complex laboratory instruments.

Using a Handheld Conductivity Meter

This is the most common and user-friendly method, suitable for field measurements and routine monitoring.

Step-by-Step Guide:

-Calibrate the Meter

Before use, calibrate the meter using standard buffer solutions. Follow the manufacturer’s instructions for calibration.

-Rinse the Electrode

Rinse the probe with distilled or deionized water to remove any residues from previous measurements. Gently blot dry with a soft tissue—do not rub.

-Immerse the Probe

Submerge the electrode fully in the water sample. Make sure the sensing area is completely covered.

-Stir the Sample (if needed)

Gently stir the water to ensure the sample is homogeneous, especially if there might be stratification.

-Take the Reading

Wait for the reading to stabilize. Most digital meters display the result within a few seconds. Record the value along with the temperature.

-Rinse and Store

After measurement, rinse the probe again and store it in a storage solution (often provided by the manufacturer) to prevent the sensor from drying out.

Y600-A&Y521-A Handheld Electrical Conductivity Meter-Water Quality Sensor Manufacturer-Yosemitech

Summary

Measuring conductivity in water is a fundamental practice in water quality assessment, offering valuable insights into the presence of dissolved ions and overall purity. Whether you're a scientist, environmental technician, aquarist, or hobbyist, understanding how to accurately measure conductivity is essential.