A private well puts the homeowner in charge of the water supply. No city utility tests it on a schedule, so the test calendar is yours to set. In Missouri, that matters because well water comes from a mix of aquifers and geology, and conditions can vary a lot from one county to the next. This guide covers when to test and what a basic panel usually includes, written for homes across the state.
Start With a Baseline Test
If you have never tested the well, or you bought a home with an unknown history, run a full baseline before anything else. Ask the laboratory for a drinking water panel that covers bacteria, nitrate and nitrite, and the common mineral and metal indicators. A baseline gives you a reference point, so a later change means something.
Times That Call for a Test
- Once a year, as a routine check for total coliform bacteria and E. coli
- After flooding, heavy runoff, or a stretch of heavy rain that saturates the ground around the wellhead
- After any pump, pressure tank, or wellhead repair, or after the well has been opened
- When taste, odor, color, or clarity changes without an obvious cause
- When staining, scale, or a sudden change in how soap lathers appears
- After a nearby septic failure, fuel leak, farm chemical spill, or new construction close to the well
- When a new owner moves in, or when an infant lives in the home or visits often, since guidance on nitrate often singles out infants and households may want to test sooner
- Before you buy a home with a private well, as part of the sale process
Missouri Conditions That Change the Plan
Much of Missouri sits over limestone and dolomite bedrock. In karst areas, water can move quickly through cracks, sinkholes, and openings in the rock. That path can carry surface water and bacteria into a well faster than a homeowner might expect. Shallow wells, wells with damaged or missing casings, and wells near ponds, streams, or drainage swales deserve closer attention. Rural homes with livestock, row crops, or older septic systems have additional reasons to test more often.
What a Basic Panel Usually Covers
Bacteria
Total coliform bacteria are a general indicator of whether a well may be getting surface influence or has a sanitary gap. E. coli is tested because its presence points more directly to fecal contamination. A positive result for either calls for prompt follow-up with the laboratory and a plan to disinfect the system and retest.
Nitrate and Nitrite
These are nitrogen compounds that can come from fertilizer, manure, and septic effluent. Results are reported as a concentration and compared against drinking water standards. Because guidance on nitrate often singles out infants, a household with young children should review a result near the limit with the laboratory or a health professional.
Mineral and Metal Indicators
Hardness, iron, manganese, and pH explain much of the staining, scale, and taste complaints people notice in daily use. Sulfate and chloride can affect taste and the behavior of plumbing. Total dissolved solids gives a broad picture of how much material is dissolved in the water. These results shape treatment choices, so read them together rather than one at a time.
Optional Tests Based on Location
Arsenic, lead, radon, volatile organic compounds, and pesticides are not part of every basic panel. Consider them if the geology, nearby land use, or a past spill suggests a reason. Radon in water is a specialized test, and a laboratory can explain what it measures and how to collect the sample.
Collecting the Sample Correctly
- Use the bottle and instructions supplied by a laboratory certified for drinking water testing in Missouri
- Do not rinse the bottle or touch the inside of the cap
- Sample from a cold tap that draws directly from the well, before any filter or softener
- Remove aerators and clean the faucet opening first if the laboratory asks for it
- Keep the sample cold and deliver it within the time window the laboratory specifies
- Record the date, time, and any recent events on the chain of custody form
Keep a Simple Record
Store every report in one place and note the date, the laboratory, and the parameters tested. Comparing results over several years shows trends that a single test cannot. If a result is unexpected, ask the laboratory to explain the method and reporting limits, and consider a confirmation sample before making major decisions.
When to Bring in Help
If bacteria are found, if nitrate is high, or if the well has had structural damage, contact a licensed well contractor or your local health authority for guidance. A test result tells you what is in the water, but it does not show where the problem enters the system. Keep your records handy when you make that call, since they help whoever investigates the well understand what changed and when.