If your home in O'Fallon draws water from a private well, bacteria testing is one of the most useful checks you can make. Coliform bacteria and E. coli are the two groups most often tested for, and the Missouri State Public Health Laboratory offers free or low-cost testing for both. Bacteria can enter a well through a damaged cap, a cracked casing, a poorly sealed wellhead, or surface water that seeps downward. Shallow wells are the most exposed, so they deserve the most regular attention.
What the Test Tells You
Coliform bacteria are a broad group found in soil, plants, and surface water. Their presence suggests that outside material may be getting into the well. E. coli is a more specific member of that group, and its presence points to contamination from animal or human waste. Neither test catches every possible problem in water, and a clean result describes one sample on one day, not every day after.
Before You Collect the Sample
- Call the lab first to confirm current bottles, sampling days, and drop-off hours.
- Use only the sterile bottle the lab provides. Do not rinse it or remove any preservative inside.
- Do not touch the inside of the cap or the lip of the bottle with your fingers.
- Avoid sampling during or right after heavy rain, flooding, or snowmelt, since those conditions can change what the water contains.
Collecting the Sample Safely
- Choose a cold water faucet that draws directly from the well line, ideally before any softener, filter, or ice maker branch.
- Remove the aerator or screen from the faucet and wipe the outlet with a clean cloth.
- Run the cold water at a steady flow long enough to clear the line.
- Fill the bottle without letting it touch the faucet, then cap it, label it with the date and time, and keep it cool until delivery.
Sampling before treatment matters. A softener or carbon filter can change the readings for some substances, and a sample taken after treatment does not show what the well delivers.
Reading the Results
Labs usually report coliform and E. coli as present or absent. Absent for both is the result you want. If either is present, the lab report should explain the next step, which commonly includes inspecting the wellhead, checking the surrounding ground, and having the well disinfected and retested. Do not assume a softener or a filter will remove bacteria. Treatment equipment is built for other jobs, and bacteria can grow inside it if the system is not maintained.
Checks Around the Wellhead in O'Fallon
Many wells in O'Fallon sit near lawns, driveways, septic fields, or cropland. Look at the well cap and casing for cracks, loose fittings, or gaps where insects, water, or debris could enter. Confirm that the ground slopes away from the casing and that no downspout or drainage path runs toward it. If the well is shallow or the cap is older, a licensed well contractor can tell you whether the seal is intact and whether the setup meets current expectations for your property.
When to Retest
- After any repair to the pump, pressure tank, well cap, or piping.
- After heavy rain, flooding, or a spring thaw.
- When the water changes in color, smell, or taste.
- On the schedule that a lab or well professional recommends for your specific well.
Keeping Your Records
Keep every lab report in one folder with the sample date, the faucet you used, and any repairs or changes to the well. A simple log makes patterns easier to spot and gives a well professional the history they need. Iron bacteria, which often show up as slime and rust-colored staining, are tested separately, so ask the lab about that test too if your fixtures or toilet tank show those signs.