Conductivity

Research

What is it?

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 it important?

Every body of water has its own unique conductivity level, based on their bedrock. It is important to establish a baseline with conductivity as some bodies of water have naturally high conductivity.

What does it mean?

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 conductivity 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 (3:20)

Water Rangers Testing Protocol

Conductivity is measured by placing a conductivity probe in the water and measuring the flow of electricity between the electrodes.

  1. Pull off bottom cap. It can be a bit tough, but it’s a ‘pull’!
  2. Turn on the conductivity meter by pressing the top buton.
  3. Dip conductivity 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 temperature and conductivity remain steady for 30 seconds.
  4. Press the ‘hold’ button (middle button). (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)
  5. Pull up meter and read the conductivity and temperature readings. We record in µS (micro-siemen), so check the units. If you get a reading like
    1.3, it is converting it to mS (milli-siemen) and you must multiply 1.3 by 1000 and record 1,300 in your form.
  6. Make sure you turn off the device after use to preserve battery life (top button).

Top value is conductivity, and the bottom value is temperature.  So, this reading, done in winter in a stream has a conductivity of 161 and a temperature of 15 °C . These devices always adjust the conductivity based on temperature, so it’s important to record both values. These readings only work while the sensor is in the water.

How to test for conductivity

A quick start guide (1:47)

Taking care of your conductivity meter

Since the conductivity meter is conducting an electric current, it is so important to keep the electrode clean. Rinse electrode in distilled water often, and especially if you are taking samples where readings are high or if the area is polluted.

Calibration

[Calibration diagram] Please note, one pouch are available to those who have purchased a testkit. For additional pouches, please contact us.

Ask an expert

Conrad Gregoire, Chemist, how to test and use a reference to make sure you’re accurate (10:27)

Contributing to the community!

Water Rangers is citizen-scientist led. So, if you have any questions, ideas, or notice any errors related to conductivity, please tell us!