If your home in or around St. Charles runs on a private well, the weeks after heavy rain or spring flooding are a good time to check your water. The city's public water report describes tap water as hard, but a private well is its own system. It draws from the ground, often from the Missouri River alluvial aquifer, and it can change when surface water moves downward after a storm. This guide covers what to test for, how to collect a sample, and what to do with the results.

Why Flood Season Matters for a Well

Floodwater carries soil, runoff, and whatever is on the ground, including livestock waste, fertilizer, and debris. When water pools around a well head or seeps through cracks in a poorly sealed casing, it can carry surface contaminants straight into the supply. Even a well that tested fine last year can change after a wet season. Shallow wells and wells with damaged caps, loose seals, or low ground around them are the most exposed.

The Main Tests to Consider

A standard panel for a private well near St. Charles usually looks at a few groups of substances. Ask the lab which tests it runs and make sure each one matches your concerns.

  • Coliform bacteria and E. coli: These indicate whether surface water or runoff may be reaching the well. A positive result means you should act right away, not wait.
  • Nitrate: Nitrate often comes from fertilizer and farm runoff. It is commonly found in agricultural areas, so it is worth testing if you live near fields or pastures.
  • Hardness, iron, and manganese: These are the mineral problems behind scale, orange or red staining, and black staining. They do not spread bacteria, but they affect fixtures, laundry, and softener performance.
  • pH and hydrogen sulfide: pH shows how acidic or basic the water is. Hydrogen sulfide produces the rotten-egg smell and can corrode metal plumbing.
  • Radium and uranium: These occur naturally in some groundwater in the region. Homes near the documented Weldon Spring legacy site may want to ask specifically about radionuclides when they order a panel.

How to Collect a Clean Sample

A lab can only tell you what is in the bottle you send, so sampling technique matters. Use the sample container the lab provides, and do not rinse it or pre-fill it. Run the cold tap for a few minutes first, then collect the water without touching the inside of the bottle or the lid. Keep the sample cool and get it to the lab within the time the lab specifies. Write down the date, the sampling location, and any recent rain or flooding, since the lab may ask for that information.

What to Do While You Wait

If a bacteria result comes back positive, or if your water looks cloudy, smells strange, or changes after a storm, avoid drinking it untreated. Boil water for drinking and cooking until a retest comes back clean, and do not rely on a softener to address bacteria. Softeners exchange minerals and do not disinfect. A licensed well contractor or your county health office can help you decide on disinfection and any repairs to the well head or casing.

Checks You Can Do at Home

Between lab tests, walk the area around your well after a storm. Look for standing water near the well cap, cracks in the concrete pad, a cap that no longer seals, and vent screens that are clogged or missing. Confirm that the ground slopes away from the well. Keep a simple record of any changes in taste, color, odor, or pressure. A short written log helps you and any technician spot patterns over time.

Reading Your Results

Lab reports list each substance with a result and often a reference level. Read the notes at the bottom of the report, since they explain whether a result needs action. If you do not understand a result, ask the lab to explain it in plain terms. Keep your reports together so you can compare them over the years. A well that is retested on a regular schedule, and after each major flood, gives you a clearer picture than a single test taken at one point in time.

Next Steps

Start by checking your well cap and grading, then order a bacteria test and a panel that covers your local concerns. Adjust the rest of your testing based on the results and on what you see around your property. Flood season is the right time to do this, and a few careful checks now can save you guesswork later.