Our treated drinking water is routinely monitored using scientific methods and highly precise instrumentation that provide much more accurate and reliable results than home test strips. Laboratory testing can measure nitrate concentrations with significantly greater precision and quality control than color-based strip tests.
If you’re looking for a quick screening tool, several reputable brands offer nitrate test strips for home use, including Watersafe, Hach, and Industrial Test Systems (ITS) SenSafe products. These can provide a general indication of whether nitrate may be present in your water.
If you decide to use a home test strip, here are a few things to look for:
- Choose strips that specifically measure nitrate (NO₃⁻) and not just nitrite (NO₂⁻).
- Pay attention to the measurement units. Nitrate test kits may report results as nitrate (NO₃⁻) or as nitrate-nitrogen (NO₃-N). These are different units, and the numbers are not interchangeable. The EPA drinking water standard is 10 mg/L as nitrate-nitrogen (NO₃-N), which is equivalent to approximately 45 mg/L as nitrate (NO₃⁻). Be sure you understand which unit your test kit uses before comparing results to drinking water standards.
- Check the detection range. For drinking water, you’ll want a test that can clearly identify levels around the EPA drinking water standard of 10 mg/L nitrate-nitrogen (NO₃-N).
- Follow the manufacturer’s instructions carefully. Accuracy depends on more than just reading the strip at the correct time. Be sure to follow directions for how long to immerse the strip in the water, whether excess water should be shaken off, how the strip should be positioned while developing, and exactly when the color comparison should be made.
- Pay attention to expiration dates and storage conditions. Heat, humidity, and age can reduce accuracy.
- Use good lighting when comparing colors to the manufacturer’s chart.
- Treat results as a screening tool, not a definitive measurement.
Nitrate concentrations generally do not change as treated water moves through the distribution system. Des Moines Water Works in the contract operator that operates the Fleur Drive Water Treatment Plant and State Certified lab on behalf of Central Iowa Water Works, if you’re interested in the nitrate level being delivered to your home, you can view DMWW’s recent nitrate results on the DMWW website at www.dmww.com. These results are generated using certified laboratory methods and provide a more accurate picture of nitrate concentrations in the water supply than a home test strip.
Our regional system utilizes seven water treatment plants, six others in addition to the Fleur Drive Water Treatment Plant. Depending on where you receive water in the CIWW system, you could receive water with different characteristics than water that is delivered from the Fleur Drive Water Treatment Plant. In that case, your nitrate concentration reading could be lower or different than those reported from the Fleur Drive Water Treatment Plant. At no time should your reading be higher than 10 mg/L unless a Nitrate MCL Exceedance Notice has been issued. This has not occurred in more than thirty years.
In short, laboratory analysis remains the gold standard for making decisions about drinking water safety. If a home test result raises concerns, we recommend confirming it through a certified laboratory before taking action.
Learn more about the Iowa State Hygienic Laboratory by following this link: https://shl.uiowa.edu/overview
Learn more about the current water quality at our plants and in our source water by following this link: https://ciww.gov/current-and-historical-source-water-quality-data-where-to-find-it/