Water Test Results Centre
How to read a nitrate result.
The 10 mg/L as nitrogen MAC, infant risk, agricultural wells, and why RO claims must match the contaminant.
Unit
Usually mg/L as nitrogen (nitrate-N). Confirm the lab did not report nitrate as NO₃ without conversion.
Canadian reference
The Canadian MAC for nitrate is 10 mg/L as nitrogen. It matters most for infants and some medically vulnerable people.
Possible sources
Fertilizer, septic systems, manure, and some geology. More common on shallow rural wells.
What one result cannot conclude
- A spring result can differ from a fall result.
- Nitrate does not tell you about bacteria or pesticides unless those were tested.
Sensible follow-up testing
- If the result approaches 10 mg/L, resample and talk to the lab or public health.
- Use an alternate drinking supply for infant formula when advised.
Source correction
Where a nearby septic or agricultural pathway is identified, fixing that pathway is part of the solution — treatment alone may not be enough long term.
Certification questions
Some reverse-osmosis systems certified to NSF/ANSI 58 carry nitrate reduction claims. Confirm the exact model listing; RO certification alone is not a nitrate promise.
Treatment options
Point-of-use RO with the right claim is a common drinking-water approach. Whole-home nitrate treatment is specialist work.