If you are looking at a home in O'Fallon that is not connected to a city water line, the well is part of the purchase. A house with a well brings its own water records, equipment history, and maintenance habits, and most of that information does not appear on the listing. Before you make an offer or move toward closing, these are the questions worth asking and the checks worth scheduling.
Start With the Paperwork
Ask the seller for any well records they have. The most useful items are the well construction record, which usually shows how deep the well is and what kind of formation it draws from, and any service notes from past pump or pressure tank work. A shallow well and a deep bedrock well face different concerns. Shallow wells are more exposed to surface water, nearby row-crop fields, and septic systems, which can allow nitrates and coliform bacteria to enter. Deep bedrock wells can carry naturally occurring radium, gross alpha, and uranium. If the seller cannot locate the construction record, ask the local or state office that handles well permits whether one is on file for the address.
Ask About Past Test Results
Next, ask when the water was last tested and what was tested for. A recent lab report is far more useful than a verbal assurance that the water is fine. Look for results covering coliform bacteria and E. coli, which tell you whether the well has been exposed to contamination pathways. Also look for iron, manganese, hardness, and nitrate. Ask whether the seller has noticed a rotten-egg smell, black slime in toilet tanks, orange or black staining in sinks, or sediment in glasses. Those signs point to specific causes such as iron bacteria, hydrogen sulfide, or sediment, and they tell you what to test for next.
Look at the Equipment
- Pump and pressure tank: their age, whether they have been replaced, and whether the seller has receipts.
- Existing treatment: any water softener, filter, or iron system, and whether it has a documented service history.
- Well cap and casing: whether the top is sealed and free of cracks, and whether the ground around it slopes away from the well.
- Septic location: where the septic tank and drain field sit relative to the well, and when the septic was last pumped.
- Flooding history: whether the property or well has been covered by floodwater or surface water over the casing.
Schedule Your Own Testing
A seller's results describe the water on the day it was collected, so plan to test it yourself before closing. The Missouri State Public Health Lab offers coliform, E. coli, and iron bacteria testing at low or no cost, which makes it a practical starting point for a home purchase. Many buyers add a broader lab panel that covers nitrates, metals, and radioactive elements such as radium, gross alpha, and uranium, especially if the well is deep or sits near farm fields. The tests you choose should match the well type and the signs you noticed during your walkthrough.
Sampling instructions matter. Follow the lab's bottle and collection directions exactly, and ask how quickly the sample must reach the lab. A sample collected from an unprepared faucet can give misleading results, and a misleading result can send you in the wrong direction.
Read the Results Together
Put the seller's records and your own results side by side. If coliform or E. coli appears, the well needs disinfection and a closer look at the cause before anyone uses it for drinking. If iron or hydrogen sulfide is the issue, the right approach depends on which one is present, and a targeted test can narrow that down. If nitrate or radioactive elements are elevated, you have a source question to answer, not just a treatment question. Write down what you learned, and ask the seller to explain anything that does not match the records.
Negotiate With What You Find
A well with clean results and solid records is a strong position for you as a buyer. A well with missing records, unresolved bacteria results, or a septic system close to the wellhead is a reason to ask for a repair, a credit, or more time to test. Your real estate agent or attorney can help frame those requests. Keep the focus on what the results show and what a repair would involve, rather than on assumptions about the property.
A private well remains your responsibility after closing, so the questions you ask now will also shape how you maintain it. Ask the seller about their routine, the pump's history, and any treatment they relied on. A clear picture on the day you buy makes the first year of ownership far easier in O'Fallon.