Can I boil the water and drink it?

Do not drink untreated well water from a flooded well. CDC says use bottled water or another safe source. If you cannot get other water, boiling kills germs; follow your health department’s boil-water instructions. Boiling does not remove chemicals. Stay on other water until a certified lab reports coliform absent.

Guide · Updated October 11, 2026

Well flooded? What to test and when

Direct answer

If floodwater covered the well cap, do not drink it. Leave the pump off until an electrician or well contractor says the wiring is dry, then disinfect with your state’s instructions. Test total coliform and E. coli first, then nitrate, at a certified lab — and retest after the chlorine is gone.

What to test
What to test	Why	EPA MCL / SMCL or guidance
Total coliform	CDC’s annual floor for a private well. A present result is a pathway warning, not a shopping trip.	Present/absent — any detected coliform is a positive until a clean retest CDC well-testing guidelines
E. coli	CDC: a positive fecal-coliform or E. coli result likely means feces got into the well. After a flood, this is the first health-department line.	Present/absent — any detected E. coli is a same-day health-department call CDC well-testing guidelines
Nitrate as N	Same yearly panel as coliform. A result at or above the public-system line goes to the health department.	10 mg/L as N (EPA public-system MCL) EPA National Primary Drinking Water Regulations

If floodwater reached the wellhead, treat the well as unsafe until a certified lab says otherwise. Other water first, electricity second, disinfection third, bacteria then nitrate last. This is not a recipe, not a product list, and not medical advice. Dose and who may work on the well belong with your state bulletin and a licensed contractor.

CDC: private wells are not city water; test yearly for total coliform, nitrates, TDS, and pH; and test after flooding, a well repair, or a change in taste, color, or smell. Use a state-certified laboratory. EPA publishes a separate after-flood briefing for private wells.

How do I know the well was affected?

Wisconsin DHS: if flood waters covered the well cap, surrounded the casing, or nearby wells were flooded, follow the flooded-well steps. Minnesota Department of Health: if floodwater covered the well or may have entered it, assume contamination. Maine CDC: if flood water covered the well cap, drinking water may be contaminated.

EPA’s after-flood briefing and those state pages name the same signs:

The wellhead or cap was submerged, or floodwater stood around the casing.
The cap is missing, loose, or not a sanitary seal. EPA: sediment and flood water can enter an uncapped well.
Casing or hardware looks cracked, loosened, or collapsed. EPA: flood water can loosen hardware, distort casing, or collapse a well.
Nearby septic flooding. EPA: drain fields will not work until groundwater recedes; septic lines may have broken. CDC lists flooded sewers and septic systems among nitrate sources.

Minnesota flags a near miss: if floodwater came within 50 feet but did not reach the well, MDH still wants a coliform test, without a disinfection first. That is not a clean bill for a submerged cap.

Do not drink it

EPA: people drinking or washing with water from a flooded private well risk getting sick. CDC: if the well is contaminated, or you suspect it is, do not drink it. Use bottled water or another safe source and call the local health department.

Wisconsin DHS: use unaffected water for drinking, food, and hygiene until the well tests free of bacteria. Do not use refrigerator ice. Safe water on that page is bottled water, tap water boiled one minute, or a well that was not flooded.

If you cannot get other water, CDC says boiling kills germs. Follow boil-water instructions. Boiling does not remove chemicals. CDC: if the well has chemicals, do not drink or use it until it is treated. Texas TCEQ: a full boil for two minutes, then cool. Use the boil time your health department printed.

When is it safe to turn the pump on?

Not while the pit is wet. EPA: do not turn on the pump. There is danger of electrical shock and damage if the well or pump has been flooded. After waters recede and the electrical system has dried, do not turn equipment on until a qualified electrician, well contractor, or pump contractor has checked the wiring. If the control box was submerged, components must be dry first. Rubber boots and gloves are not adequate protection from shock.

Maine CDC: once water has receded and power to the pump is off, remove the cap and inspect. You may need a well driller, pump installer, or electrician. Restore power only after that inspection.

Minnesota: using the well pump to clean sediment out of a flooded well can ruin the pump. Hire a licensed contractor. EPA: silt in pumps, valves, and gears can burn them out.

Disinfection (shock chlorination) basics

Shock chlorination is a one-time chlorine dose through the well and plumbing, a wait, a flush, then a retest. It is a procedure, not a filter. It does not remove nitrate, pesticides, or metals. EPA: disinfection will not protect against those non-biological contaminants.

This page will not give a bleach recipe. Use your state’s instructions, or hire the license that state names.

Wisconsin. DHS wants a licensed well driller or pump installer. DNR also publishes an owner disinfection procedure and still prefers a contractor.
Minnesota. MDH: disinfecting flooded private water wells. If floodwater covered the well or may have entered it, hire a licensed contractor to inspect, clean sediment if needed, then disinfect.
Pennsylvania. DEP flooding resources point to disinfection after the water recedes: disinfection of home wells and springs.
Texas. TCEQ: do not use the well until floodwaters recede, the well and plumbing are disinfected, and a lab shows no bacteriological contaminants. Disinfecting Your Private Well (GI-432).
Maine. Maine CDC’s Flooding and Your Well: inspect, shock, flush, then test.

A one-time shock versus a lamp that stays on is UV vs. shock chlorination. A flooded well is the shock side of that table, after the health department.

What to test after

Bacteria first. Nitrate second.

Total coliform and E. coli. CDC: a high total-coliform count means harmful germs are likely on the same path; a positive fecal coliform or E. coli result likely means feces got into the well. Wisconsin DHS and DNR, Minnesota, Pennsylvania DEP, Texas TCEQ, and Maine CDC all send a flooded well to a certified or accredited lab for coliform — and, where they name it, E. coli — before the well goes back in service.

Nitrate as N. CDC’s yearly floor includes nitrates. Flooded sewers, septic systems, and fertilizer runoff are named sources. EPA’s public-system MCL is 10 mg/L as N. A result at or above that line still goes to the health department. Disinfection does not fix nitrate. A hardware-store strip is not a flood clearance.

A present coliform after a flood is expected until disinfection and a clean retest. The later bacteria-sheet reading order is Coliform Bacteria in Well Water.

When should I retest?

Not while chlorine is still in the plumbing. Leftover shock hides bacteria or gets the sample rejected.

EPA: test bacteria 7 to 10 days after disinfection. Pennsylvania DEP: wait at least 5 days after a shock; once chlorine-free, wait 2 to 5 days more, then resample. Wisconsin DNR: wait about a week, then resample. Minnesota: after a safe result, retest in two to four weeks. Penn State Extension, on shock generally: 10 to 14 days, then again in two to three months if that result is clean.

Use the interval your state printed. The pattern is one test after the chlorine is gone (about 1–2 weeks), then another in the following weeks or months. Wisconsin DNR also wants another test a month after a negative. EPA: groundwater can keep a well unsafe for many months; repeated testing is part of the work.

If bacteria are still present, stay on other water. Confirm the sample, then inspect: another disinfection, a repair, or both. Pennsylvania: boiled or bottled water until coliform is absent. Texas: disinfect and repeat until total coliform is absent.

Where to get a test

Use a state-certified drinking-water lab. Start at certified labs by state, then your state’s inventory. Counties sometimes hand out flood bottles. This page does not sell a kit.

Michigan

Labs: Michigan certified labs
Use the EGLE-certified drinking-water path on that inventory. Do not invent a flood fee or a county bottle from this page.

North Carolina

Labs: North Carolina certified labs
Use the county environmental health program or the NCSLPH certified-lab search. Do not invent a flood fee from this page.

A later bacteria sheet still reads in this order: Coliform Bacteria in Well Water, then how to read a well water lab report. A one-time shock versus a lamp that stays on is UV vs. shock chlorination. A hardware-store strip is not a flood clearance — well water test kits.

Bottom line

If the cap was under water, do not drink it. Leave the pump off until an electrician or well contractor says the wiring is dry. Disinfect with your state’s instructions. Test total coliform and E. coli first, then nitrate, at a certified lab. Retest after the chlorine is gone, then again on your state’s calendar. This site is not medical advice.

FAQ

How do I know the well was affected?: If floodwater covered the well cap, stood around the casing, or nearby wells were flooded, state health pages treat the well as affected. EPA also flags a missing or loose cap, cracked or loosened casing, and nearby septic flooding. Minnesota still wants a coliform test if floodwater came within 50 feet but did not reach the well.
Can I boil the water and drink it?: Do not drink untreated well water from a flooded well. CDC says use bottled water or another safe source. If you cannot get other water, boiling kills germs; follow your health department’s boil-water instructions. Boiling does not remove chemicals. Stay on other water until a certified lab reports coliform absent.
When is it safe to turn the pump on?: Not while the area is wet. EPA: do not turn on the pump after a flood until floodwaters have receded, the electrical system has dried, and a qualified electrician or well or pump contractor has checked the wiring. Rubber boots and gloves are not adequate protection from electric shock.
When should I retest?: After disinfection, wait until chlorine is gone. EPA says test bacteria 7 to 10 days later. State pages cluster around one to two weeks, then another test weeks to a few months later (Penn State: 10 to 14 days, then two to three months). Use the interval your state printed.

State pages and the labs hub

Sources

1.CDC. Guidelines for Testing Well Water.
2.CDC. Guidelines for Treating Well Water.
3.U.S. EPA. What to Do With Your Private Well After a Flood.
4.U.S. EPA, Private Wells. Protect Your Home’s Water.
5.U.S. EPA. National Primary Drinking Water Regulations.
6.Penn State Extension. Shock Chlorination of Wells and Springs.
7.Wisconsin Department of Health Services. Flooding: Private Wells.
8.Wisconsin Department of Natural Resources. Recommendations for private wells inundated by flooding.
9.Minnesota Department of Health. Flood Precautions For Private Water Wells.
10.Minnesota Department of Health. Disinfecting Flooded Private Water Wells.
11.Pennsylvania Department of Environmental Protection. Flooding Resources.
12.Pennsylvania Department of Environmental Protection. Disinfection of Home Wells and Springs.
13.Texas Commission on Environmental Quality. After the Flood: Is Your Water Safe to Drink?.
14.Maine CDC Drinking Water Program. Flooding and Your Well: Make Sure Your Drinking Water is Safe.