Flooded Well: What to Do Before You Turn the Pump Back On
Flood water at the wellhead means the water is unsafe until proven otherwise, and the pump stays off until someone qualified has looked at the wiring. Here is the order of operations.
8 min readUpdated September 2026
Stop: Do Not Turn On the Pump
The first instinct after the water goes down is to flip the breaker and see whether the pump survived. That is the one thing not to do.
Two EPA warnings, in their words
Do not turn on the pump. There is danger of electrical shock and damage to your well or pump if they have been flooded.
Do not wash with well water. People drinking or washing with water from a private well that has been flooded will risk getting sick.
Both warnings come from EPA 816-F-05-021. They are not cautious boilerplate. A submerged control box can hold a fault that puts voltage somewhere you do not expect, and rubber boots and gloves are not adequate protection from electric shock. Power goes back on after a qualified electrician, well contractor, or pump contractor has checked the wiring, and after every electrical component is dry.
Meanwhile, treat the water as unsafe. Not bad-tasting, unsafe. Use bottled or hauled water for drinking, cooking, and washing until a test says otherwise.
If you are on a boil-water notice
Boiling handles bacteria. It does not remove chemicals, fuel, or heavy metals, and it concentrates some of them. Follow your health department's drinking and bathing advisories rather than assuming boiling covers a flood.
Inspect the Well and Pump
Flood damage to a well is often invisible from the surface, so age and depth matter more than what the wellhead looks like.
10 years or 50 feet
EPA: wells older than 10 years or shallower than 50 feet are likely contaminated after a flood, even with no apparent damage
Fast-moving flood water carries debris heavy enough to loosen well hardware, dislodge construction materials, or distort the casing. Coarse sediment erodes pump components. If the well was not tightly capped, sediment and flood water went straight in. Floods can collapse a well outright.
Sediment is also what kills the pump after the flood rather than during it. Valves and gears need the silt and sand cleaned out, and a pump that is not cleaned and properly lubricated can burn out. A well or pump contractor cleans, repairs, or maintains the pump before it runs again.
Before anyone restores power
As needed
Work through this with your contractor, not alone.
Confirm the flood water has receded and the equipment is dry
A submerged control box needs every component dry before service is restored.
Have the wiring checked by a qualified electrician or well contractor
This is the step EPA names specifically. It is not optional.
Check the well cap and casing for damage or movement
A cracked or displaced cap is an open path for surface water. See our guides to well caps and well casing.
Have the pump cleaned of silt and sand
Sediment in the valves and gears burns pumps out.
Look around the property for washed-in chemical containers
Drums and barrels that moved onto your land are a call to the state or county health department, or the Superfund Hotline at 1-800-424-9346.
EPA is direct about who should do this: drilled, driven, and bored wells are best disinfected by a well or pump contractor, because it is difficult for an owner to disinfect them thoroughly.
The procedure below is EPA's, reproduced in order. Before you start, check the condition of the well and make sure there is no exposed or damaged wiring. If you see any damage, call a professional instead of continuing. Contact your local or state health department or agriculture extension agent for advice specific to your well, because these steps are meant to supplement flood precautions issued by state and local health authorities.
EPA emergency disinfection of a flooded well
As needed
Step 1. Run the water clear
If the water is muddy or cloudy, run it from an outside spigot with a hose attached until it comes clear and free of sediment.
Step 2. Gather materials
One gallon of non-scented household liquid bleach, rubber gloves, eye protection, old clothes, and a funnel.
Step 3. Open the well
Work out how bleach gets into your well. Some wells have a sanitary seal with an air vent or a plug that comes out. On a bored or dug well the entire cover lifts off.
Step 4. Pour in the bleach
Carefully pour the gallon of bleach down into the well casing, using the funnel if you need one.
Step 5. Circulate it into the well
Run water from an outside hose back into the well casing until you smell chlorine coming from the hose, then shut the outside hose off.
Step 6. Pull it through the house
Turn on every cold water tap inside and outside until you can smell chlorine at each one, then shut them all off. Switch any water treatment system to bypass before you open the indoor taps.
Step 7. Wait 6 to 24 hours
Do not drink, cook, bathe, or wash with the water during this window. It holds a high concentration of chlorine.
Step 8. Flush the system
Open an outside spigot with a hose and run the water somewhere it will not reach plants, lakes, streams, or the septic tank. Run it until the chlorine smell is gone, then shut it off.
Step 9. Retest for bacteria
Have the water tested for bacteria 7 to 10 days after disinfection.
Chlorine has a hard limit
Well disinfection will not protect you from pesticides, heavy metals, or other non-biological contamination. If a fuel tank, chemical store, or industrial site near your well was also flooded, you need a different test panel and special treatment. Chlorine does nothing for any of it.
Our standing well chlorination guide covers routine shock chlorination, which uses the same chemistry for a much less urgent reason.
Testing the Water
The test that matters happens 7 to 10 days after disinfection, not the day after.
Contact your local health department to have the water sampled and tested, or call your state laboratory certification officer to find a certified lab nearby. If the health department issues sterile bottles for you to collect the sample yourself, follow the bottle instructions exactly. A sample collected into the wrong container tells you nothing.
After the pump is back in operation, EPA advises that the health department sample and test the water at regular intervals rather than once.
What to ask the lab for after a flood
Test
Why it is on the list
When
Total coliform and E. coli
The standard indicator that surface water or sewage reached the well
7 to 10 days after disinfection
Nitrate
Flooded septic systems and farm runoff both raise it, and it is the one that matters most for infants
With the first post-flood sample
Anything specific to what flooded upstream
Fuel, solvents, pesticides, or metals if a tank, farm store, or industrial site went under. Chlorination does not touch these
This is the part of the EPA guidance that gets skipped, and it is the part that catches people out months later.
EPA caution, quoted
Because of the extensive flood area and the speed and direction of ground water flow, your well may not be a safe source of water for many months after the flood. The well can become contaminated with bacteria or other contaminants. Waste water from malfunctioning septic tanks or chemicals seeping into the ground can contaminate the ground water even after the water was tested and found to be safe.
Read that carefully. A clean result on day 10 is a snapshot of your well on day 10. Groundwater keeps moving, and a neighbor's damaged septic field can arrive at your well weeks later. EPA's conclusion is to take long-range precautions, including repeated testing.
Septic systems are part of the same picture. Do not use one immediately after a flood. Drain fields will not work until the underground water has receded, and septic lines may have broken.
Knowing how deep your well is and what it is screened in changes how exposed it is. If you do not have the log, our find your well record guide shows how to pull it from the state, and water table depth by address shows the depths recorded in nearby wells.
What You Can Do Yourself
The split here is unusually clear, because EPA draws it for you.
DIY-safe
Keep the pump off and the breaker off
Use bottled or hauled water for drinking, cooking, and washing
Visually inspect the well cap and casing from a safe distance
Collect samples in the bottles the health department supplies, following their instructions
Run the post-chlorination flush through an outside hose to a safe discharge area
Keep the septic system out of use until the ground has drained
Call a licensed pro
Checking and restoring the electrical system to a flooded pump
Disinfecting a drilled, driven, or bored well
Cleaning silt and sand out of the pump, valves, and gears
Any repair to a damaged cap, casing, or collapsed well
Deciding whether contamination is chemical rather than bacterial
One practical note on hiring. After a regional flood every contractor within an hour is booked, and the ones knocking on doors are not always licensed. Our licensed contractor directory lists contractors by state and county with their license status, and well pump service near me narrows it to pump work. Our guide to well inspection covers what a proper post-event inspection should include.
Keep the paperwork
Well owners often hold records about how their well was constructed and tested. That information helps the health department judge water quality conditions in the area, so dig it out before the inspection rather than after.
Frequently asked questions
No. EPA is explicit about this: do not turn on the pump. There is a danger of electrical shock and of damaging the well or the pump if either has been flooded. After the water recedes and the equipment dries, the wiring has to be checked by a qualified electrician, well contractor, or pump contractor before power goes back on. If the pump control box went under, every electrical component must be dry first.
Assume it did. EPA says wells that are more than 10 years old or less than 50 feet deep are likely to be contaminated after a flood even if there is no apparent damage. A well that is not tightly capped can take in sediment and flood water directly. Swiftly moving water also carries debris that can loosen well hardware or distort the casing.
After the bleach is in the system and you have run it to every tap, wait 6 to 24 hours. During that window do not drink, cook, bathe, or wash with the water, because it holds a high concentration of chlorine. Then flush the system through an outside hose until the chlorine smell is gone, running the discharge somewhere it will not reach plants, streams, or your septic field.
Have the water tested for bacteria 7 to 10 days after disinfection. Testing on day one mostly measures leftover chlorine rather than whether the well is clean. Contact your local health department for sample bottles, or use a state-certified lab.
Not necessarily. EPA warns that because of the size of a flood area and the speed and direction of groundwater flow, a well may not be a safe source of water for many months afterward. Waste water from damaged septic tanks and chemicals seeping into the ground can contaminate groundwater after a test came back safe. Plan on repeat testing rather than a single all-clear.
No, and this is the part people miss. Disinfection kills bacteria. It does nothing about pesticides, heavy metals, fuel, or other non-biological contamination. If a flooded fuel tank, farm chemical store, or industrial site is anywhere near your well, the water needs different treatment and a different test panel. If you see chemical containers, drums, or barrels that washed onto your property, call your state or county health department.
Not right away. EPA advises that septic systems should not be used immediately after floods. Drain fields will not work until the underground water has receded, and septic lines may have broken during the flood.
EPA recommends a well or pump contractor disinfect a drilled, driven, or bored well, and restore power to a flooded pump. Search licensed contractors by state and county.
