Conductivity in well water: what µS/cm means
Conductivity measures how much dissolved salt and minerals are in your water. There is no limit. It's most useful for spotting changes: a jump since your last test can point to road salt or another source reaching the well.
- US (EPA)
- No limit.
- Ontario
- No limit.
What it is
Conductivity is how easily water carries electricity, which rises with dissolved minerals and salts. It is reported in microsiemens per centimeter (µS/cm). Multiplying by about 0.65 gives a rough TDS estimate in mg/L.
What your number means
- For contextBelow 800 µS/cm
Typical for many wells. Roughly under 500 mg/L of TDS.
- Worth a look800 to 1,500 µS/cm
Higher mineral or salt content. Check sodium, chloride and TDS.
- Worth a lookAbove 1,500 µS/cm
Salty or very mineralized. Look for road salt or other sources.
What to do
- Compare with past results. A rising trend matters more than one number.
- Check your sodium, chloride and TDS results to see what is driving it.
- A handheld meter is a cheap way to track changes between lab tests.
How often to test
With a full panel every 3 to 5 years, or yearly near salted roads.
Common questions
How is conductivity related to TDS?
TDS is roughly 0.5 to 0.7 times conductivity, depending on the minerals. Both rise when more is dissolved in the water.
Is high conductivity dangerous?
Not by itself. It's a clue: look at sodium, chloride, nitrate and other results to see what's in the water.
Sources: Ontario: testing and treating private wells. Limits checked November 2026.