Many private wells around O'Fallon draw from shallow groundwater. Water that moves through soil near farm fields and septic systems can carry dissolved nitrate with it. Nitrate has no taste, smell, or color, so a glass of water can look perfectly normal while still containing it. The only reliable way to know what is in your well is to test it.
This guide covers what to check, how to collect a sample, and what to do with the result. It does not explain what any reading means for a particular person's health. That question belongs with your lab report and a health professional.
Where nitrate can come from near home
- Fertilizer applied to nearby row crops, lawns, or pastures
- Animal waste from barns, pens, or pastures
- A septic tank or drain field uphill from or close to the well
- An older or poorly sealed well that lets surface water in
Not every well near these sources will have a problem, and a well with no obvious source can still show nitrate. Location is a reason to test, not a conclusion.
Check the well before you sample
Look at the well cap and casing. Is the cap intact with a tight seal? Is the ground graded so surface water drains away from the well? Are there cracks in the concrete pad or gaps where water could run down the outside of the casing? Write down anything that looks off, since a construction problem can matter as much as the chemistry.
Also note the approximate location of the septic tank and drain field relative to the well, and what is planted or applied on nearby land. A simple hand sketch on paper is enough to share with a lab or water professional.
How to collect a nitrate sample
- Choose a lab that accepts private well samples and ask what container it provides and how long the sample can wait before delivery.
- Use the container the lab supplies. Do not rinse it or substitute a food jar.
- Run the cold water for a few minutes before filling, unless the lab gives different directions.
- Avoid touching the inside of the lid or bottle.
- Label the sample with the date, time, and location, then deliver it on schedule.
Nitrate is often tested alongside other parameters. Ask whether the lab can add coliform bacteria and E. coli testing at the same time. The Missouri State Public Health Lab offers free or low-cost coliform, E. coli, and iron-bacteria testing for many private wells, which can be a useful starting point for a basic check.
Reading the result
A lab report lists nitrate as a concentration with a unit. Compare the result against the standard the report itself references, and keep a copy with your home records. If the result is above that standard, or if the lab notes a concern, contact a health professional for guidance on using the water in the meantime. Boiling does not remove nitrate and can concentrate it, so do not rely on boiling.
What to do if nitrate is present
- Stop using the water for drinking and infant formula until you have professional guidance
- Retest after any change to the well, septic system, or nearby land use
- Ask a qualified water professional to review treatment options, and compare them in writing before anyone visits your home
- Keep every report together so future testing has a clear history
A water softener does not remove nitrate. Hardness control and nitrate control are separate problems, so a softener alone will not address a nitrate result. When talking with any service provider, ask directly which treatment addresses nitrate and how its performance would be confirmed.
Retest on a steady schedule
Retest after flooding, heavy rain near the well, changes to septic service, new fertilizer use nearby, or any change in taste or appearance. Seasonal shifts can change readings, so date every result and compare like with like. For a home in O'Fallon, a routine of records and periodic lab checks gives you far more useful information than a single test that gets filed away and forgotten.