What is conductivity?
Conductivity is how we measure the ionic content (such as chloride, nitrate, sulfate, sodium, magnesium, calcium, or iron) in a body of water by measuring the water’s ability to conduct electricity.
Why is conductivity important?
Every body of water has its own unique conductivity level, based on its bedrock. It is important to establish a baseline as some bodies of water have naturally high levels due to their geology and geography.
What does a conductivity measurement mean for water?
We can use conductivity as an early warning system for potential problems that warrant further testing. If we see a variance (either lower or higher) from our baseline readings, we know something may have gone wrong. While lab testing is the usually the only way to determine what is causing the reading, higher readings could indicate a pollution event has taken place.
What about ocean water? Conductivity reading for ocean water is about 55,000 µS. While some people test conductivity in sea water, many meters won’t read that high. Many protocols choose to measure salinity instead. Salinity is measured in parts per thousand, with the average ocean reading measuring 35 ppt. Just like with all tests, we can convert readings, although conductivity measures everything that conducts electricity, while salinity only measures salt.
Some common values
|Distilled water||0.5 – 3 µS|
|Melted snow||2 – 42 µS|
|Has effects on fish reproduction||over 500 µS|
|Tap water||50 – 800 µS|
|Potable water||30 – 1500 µS|
|Freshwater streams||100 – 1,000 µS|
|Industrial wastewater||10,000 µS|
|Sea water||55,000 µS|
E.g. Most readings for the Ottawa river are below 100 µS, but near a storm sewer could have conductivity values over 2,000 µS (or 2.0mS).
Ask an expert
Conrad Gregoire, Chemist, introduces Conductivity
Water Rangers Testing Protocol
Note: old models have a cap you need to remove. If you purchased your meter after 2021, you will not have a cap.
- Turn on the meter by pressing the top button.
- Dip the meter into the water. Do not dunk the whole device in as the battery is near the top. Hold in the water for 2 minutes, swishing it around lightly. Continue until both values remain steady for 30 seconds.
- Tip: If you get a reading of 10 or less, you have not removed the cap or you have taken the sensor out of the water before reading) Read the measurements. We record in µS/cm (microsiemens per centimetre), so check the units. If you get a reading like 1.3, it is converting it to mS (millisiemens) and you must multiply 1.3 by 1000 and record 1,300 in your form.
- Make sure you turn off the device after use to preserve battery life (top button).
How to test for conductivity
Taking care of your conductivity meter
Since the probe is conducting an electric current, it is so important to keep the electrode clean. Rinse electrodes in distilled water often, especially if you are taking samples where readings are high or if the area is polluted.
Ask an expert
Conrad Gregoire, Chemist, how to test and use a reference to make sure you’re accurate.
Get started with testing conductivity here:
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