Floodwater can reach a private well through the ground around the casing, through a damaged well cap, or through surface water that pools near the wellhead. In Washington and the river-bottom land around Franklin County, that risk is real after heavy rain or a high river stage. Before you disinfect anything, a few checks will tell you whether the well needs treatment and what to do next.
Start with the well itself
Walk the area before you touch the pump. Look at the well cap, the vent screen, and the top of the casing. Check whether the ground around the wellhead has settled, cracked, or washed away, and whether silt or debris sits against the casing. A loose, cracked, or ungasketed cap can let water in directly. Note any standing water, dead animals, or fuel smell nearby, and keep children and pets away from that area until you know more.
Look for changes in the water
Water that was clear before a flood but now looks cloudy, smells musty, or leaves a film deserves attention. Sediment can come from the aquifer shifting or from surface water entering the well. Stains and odors also have ordinary causes, such as iron or hydrogen sulfide, so a change in the water is a reason to test, not a diagnosis.
Test before you assume
A lab test is the only way to know whether bacteria are present. Coliform bacteria and E. coli are the usual indicators, and a certified lab can run them on a sample you collect using its bottle and instructions. Draw the sample from a cold tap that is not behind a filter or softener, and follow the lab's collection steps closely. If the well sits near farm land or a septic system, ask for nitrate to be included too, since floodwater can move both. A home test kit can give a quick screen, but it does not replace a lab report.
Decide what to do while you wait
If the well was flooded or you suspect contamination, use a source you already trust for drinking and cooking until the results come back. Bottled water is a common stopgap while you wait. Keep written records of the flood date, the sampling dates, and the results so you can compare them later.
Disinfection is a procedure, not a quick fix
Shock chlorination is commonly used after flooding, but the right method depends on the well depth, the casing, and how the pump is installed. Mixing the wrong amount or running the system incorrectly can cause its own problems. Ask a licensed well contractor or your county health office for the procedure that fits your well, including how long the system should run and when to retest. Do not add chemicals to the well yourself without written instructions for your system.
Retest after treatment
One clean result after disinfection does not settle the question. Schedule a follow-up test after the system has run and the chlorine has cleared, and repeat testing over the following weeks if the first results were positive. Keep the lab reports with your well records so the next person who services the well has a full history.
What to check in your Washington home
- Inspect the well cap, vent, and casing after every high-water event.
- Clear silt and debris from the wellhead carefully, without disturbing the casing.
- Keep a log of flood dates, test dates, and lab results.
- Test for coliform bacteria and E. coli after any flood, even if the water looks fine.
- Ask a licensed contractor before adding chemicals or opening the well.