The water has receded, the yard is drying out, and the tap still runs like nothing happened. That's the trap. A flooded well almost always works — pump running, pressure normal, water looking clear — while carrying whatever the floodwater carried: septic overflow, livestock runoff, fuel, road chemicals, and silt loaded with bacteria.
The rule from every health department is blunt: if floodwater reached or covered your wellhead, assume the well is contaminated until testing proves otherwise. Here are the five steps, in order, and the mistakes that make flooded wells worse.
Step 1: Stop Using the Water (and Maybe the Pump)
From now until a clean test: bottled water for drinking, cooking, brushing teeth, and pet bowls. If bottled isn't available, boil at a rolling boil for one minute — that handles the microbes (not chemicals; if you smell fuel or solvent in the water, don't drink it at all, boiled or not, and don't shock-chlorinate yet — get advice from your health department first, since chlorine plus certain chemicals is its own problem).
If the wellhead or pump equipment is still underwater or the pit is flooded: leave the pump OFF. Running a submerged or silt-choked pump can destroy the motor and pull contamination deeper into the system. Flood-soaked electrical controls need to dry (or be checked) before energizing — a well electrician's 20-minute look is cheaper than a shorted control box.
Step 2: Inspect Before You Disinfect
Once things are dry and safe to approach:
- Cap and seal: Did water flow over or around the cap? Is the gasket intact? A vermin-proof sealed cap is a $40 upgrade to make now.
- Casing and grade: Look for erosion, settling, or debris impact around the casing; floods regrade the soil, and a new dip around your casing is a funnel for the next storm.
- Silt check: Run an outside spigot (bypass filters) into a bucket. Heavy silt = let the well rest and settle, and consider having it professionally flushed before disinfection — chlorinating a well full of sediment doesn't work; the chlorine can't reach microbes buried in the mud.
- Electrical: Any submerged wiring, pressure switch, or control box gets inspected before trusted.
Step 3: Shock Chlorinate the Whole System
With the wellhead repaired and the water running reasonably clear, disinfect everything the flood touched — well, pressure tank, water heater, every pipe. The complete procedure with exact bleach doses by well depth is here: How to Shock Chlorinate Your Well. The flood-specific notes:
- Use fresh bleach or a well sanitizer kit — flood recovery is not the moment for the half-degraded jug from 2019.
- Pull chlorinated water to every fixture, appliance, and outside tap; floodwater reached everything the plumbing reaches.
- Replace all filter cartridges after disinfection (they're contaminated), and put carbon filters and softeners on bypass during the chlorine soak.
- Hold 12–24 hours, flush outdoors away from the septic system, and verify zero residual with chlorine strips.
Step 4: Test Before You Trust
This is the step people skip, and it's the only one that actually answers the question. Chlorine smell gone ≠ safe. Test for total coliform and E. coli no sooner than a few days after the chlorine has fully flushed — a Tap Score Coliform Kit gives you a certified lab answer. Many health departments offer free or cheap post-flood bacteria testing; use them, they exist for exactly this.
- Clean result: resume normal use, then retest in 2–3 weeks — floods can leave slow-releasing contamination in the aquifer, and the second test is the one that proves stability.
- Positive result: repeat the shock, re-inspect for the entry point you missed, retest. Repeated positives after a flood = call in a well professional; you may need extended treatment or continuous UV disinfection.
- If the flood plausibly carried fuel or chemicals (roads, tanks, farms upstream), add a chemical panel (VOCs at minimum) to the test — bacteria kits don't see gasoline.
Step 5: Flood-Proof for Next Time
While the lesson is fresh: extend casing to 12+ inches above grade (flood-prone areas: above known flood level), regrade so water sheds away, seal conduit entries, upgrade the cap, and fix that well pit if you have one — pits are flood magnets and most modern codes ban them.
Your Action Plan (Print This One)
- Now: Bottled/boiled water only. Pump off if equipment was submerged.
- When dry: Inspect cap, casing, grade, electrical. Repair entry points.
- Then: Shock chlorinate the entire system; replace filter cartridges after.
- Test after chlorine clears. Clean → retest in 2–3 weeks. Positive → repeat.
- Harden the wellhead before the next storm season.
A flood recovery generates exactly the records you'll want later: the date, what was submerged, the chlorine dose, both test results, the repairs made. Log the whole event in the WellKept app as it happens — it schedules the retest reminders (the 2–3 week follow-up is the most-skipped step in this whole protocol), and next storm season you'll have last year's playbook in your pocket instead of in the junk drawer. Insurance adjusters and health departments also love a documented timeline.
Frequently Asked Questions
Is well water safe to drink after a flood? No — assume it's contaminated if floodwater reached the wellhead. Use bottled or boiled (1 minute rolling boil) water until the system has been inspected, shock chlorinated, and a lab coliform test comes back clean. Clear-looking, normal-tasting water proves nothing after a flood.
How long after a flood can I use my well water? Typically 1–2 weeks minimum: days for floodwater to recede and silt to settle, 24 hours for the chlorine soak, another day or two of flushing, then a bacteria test with results in 2–3 days. Resume use on a clean test, and confirm with a second test 2–3 weeks later.
Should I turn off my well pump during a flood? If floodwater is approaching or covering the wellhead, pump house, or any electrical controls — yes, shut off power at the breaker. Running a submerged pump risks motor damage and electrical hazard, and pumping during the flood pulls contaminated water deeper into your system.
How much bleach do I use to disinfect my well after flooding? The same dose as standard shock chlorination — roughly 3 pints of unscented 5–6% bleach per 100 gallons of well water, targeting 50–200 ppm through the whole system. See our step-by-step shock chlorination guide for amounts by well depth and diameter.
Do I need to replace my water filters after a flood? Yes — every cartridge (sediment, carbon, RO prefilters) that saw flood-contaminated water is now a bacteria hotel. Bypass carbon filters and softeners during shock chlorination, then install fresh cartridges after the system flushes clean, not before.