If you have a private well in or around Washington, the lab report from a bacteria test can look more confusing than it needs to. Most of the page is codes, short phrases, and sample notes. This guide walks through what the common lines mean and what a homeowner can do next. It is general information, not a substitute for advice from the lab or your local health office.
What the test is looking for
Bacteria tests on a well usually check for total coliform bacteria and, separately, E. coli. Coliform is a broad group of bacteria found in soil, plants, and surface water. E. coli is a specific type that lives in the intestines of warm-blooded animals, so its presence points more directly to recent contamination from an outside source than the broad group does. Neither test tells you exactly which organisms are present or where they came from. Those questions need follow-up.
Reading the lines on the report
Most reports list each test as present or absent, sometimes with detected or not detected wording. Look for these items:
- Sample date and collection point. A sample taken from a dirty faucet, a hose bib, or a line with a filter can produce misleading results. The report should say where the sample came from.
- Total coliform result. Absent is the result you want. Present means bacteria from that group were found in the sample.
- E. coli result. Absent is the result you want. Present is a stronger signal of contamination and calls for prompt action.
- Method or reporting notes. Some labs describe the testing approach. Keep these lines so you can compare later results.
- Lab contact and comments. Labs often add a short note about what to do when a result is positive.
Why one positive result is not the whole story
A positive coliform result on a single sample does not by itself prove the well is permanently contaminated. Sampling mistakes are common, including a contaminated faucet, a sample taken during heavy rain, or a bottle cap left loose. A common next step is resampling with a clean collection procedure. Ask the lab for sampling instructions before you collect the second sample so the comparison is fair.
Common reasons a well tests positive
In the Franklin County and river-bottom area around Washington, a few situations tend to come up when a well returns a positive bacteria result:
- Flooding or heavy runoff that reached the wellhead, the casing, or nearby surface water.
- A cracked or unsealed well cap, or a gap where surface water can enter.
- Damage to the well casing or problems with a nearby septic system.
- Recent well work, pump replacement, or repairs that may have introduced dirt or contaminated equipment.
Private wells are not regulated the way public water systems are, so no utility will test yours for you. The homeowner carries that job.
What to do after a positive result
- Follow the guidance from the lab or local health office on whether to use another source or boil water until retesting is complete.
- Check the well cap, the casing, and the drainage around the wellhead for obvious problems.
- Collect a resample using the lab's instructions, then compare the new result with the first.
- If the problem continues or you cannot find a cause, ask a qualified well professional to inspect the system and advise on disinfection. Choose someone who can explain the findings in writing.
Keeping your records
Save every report in one folder with the date, the sample location, and any notes from the lab or inspector. A history of results is more useful than a single report when you are deciding whether a problem keeps returning. Testing after flooding, after well work, and on a regular schedule is a practical habit for any private well in Washington.