Drilled, driven or bored wells are best disinfected 

by a well or pump contractor, because it is difficult 

for the private owner to thoroughly disinfect these 

wells. 

If you suspect that your well may be contaminated, contact your local or state health department 

or agriculture extension agent for specific advice on 

disinfecting your well. The suggestions below are 

intended to supplement flood precautions issued by 

State and local health authorities.

Well and Pump Inspection

Flood Conditions at the Well - Swiftly moving flood water can carry large debris that could 

loosen well hardware, dislodge well construction materials or distort casing. Coarse sediment 

in the flood waters could erode pump components. If the well is not tightly capped, sediment 

and flood water could enter the well and contaminate it. Wells that are more than 10 years old or 

less than 50 feet deep are likely to be contaminated, even if there is no apparent damage. Floods 

may cause some wells to collapse.

Electrical System - After flood waters have receded and the pump and electrical system have 

dried, do not turn on the equipment until the wiring system has been checked by a qualified 

electrician, well contractor, or pump contractor. If the pump’s control box was submerged during the flood all electrical components must be dry before electrical service can be restored. Get 

assistance in turning the pump on from a well or pump contractor. 

Pump Operation - All pumps and their electrical components can be damaged by sediment 

and flood water. The pump including the valves and gears will need to be cleaned of silt and 

sand. If pumps are not cleaned and properly lubricated they can burn out. Get assistance from a 

well or pump contractor who will be able to clean, repair or maintain different types of pumps. 

What to Do After the Flood

WARNING! 

DO NOT TURN ON THE PUMP

There is danger of electrical shock and 

damage to your well or pump 

if they have been flooded 

WARNING! 

DO NOT WASH WITH WELL WATER

People drinking or washing with water 

from a private well that has been flooded 

will risk getting sick. 
Emergency Disinfection of Wells that have been Flooded

Before Disinfection: Check the condition of your well. Make sure there is 

no exposed or damaged wiring. If you notice any damage, call a professional 

before the disinfection process.

Step 1

If your water is muddy or cloudy, run the water from an 

outside spigot with a hose attached until the water becomes 

clear and free of sediments. 

Step 2

Determine what type of well you have and how to pour the bleach into 

the well. Some wells have a sanitary seal with either an air vent or a plug 

that can be removed (a). If it is a bored or dug well, the entire cover can be 

lifted off to provide a space for pouring the bleach into the well (b).

Step 3

Take the gallon of bleach and funnel (if needed) and carefully pour the bleach down 

into the well casing. 

Step 4

After the bleach has been added, run water from an outside 

hose into the well casing until you smell chlorine coming from the hose. Then turn off the 

outside hose. 

Step 5

Turn on all cold water faucets, inside and outside of house, until the chlorine 

odor is detected in each faucet, then shut them all off. If you have a water treatment system, switch it to bypass before turning on the indoor faucets. 

Step 6

Wait 6 to 24 hours before turning the faucets back on. It is important not to drink, cook, 

bathe or wash with this water during the time period --- it contains high amounts of chlorine. 

Step 7

Once the waiting period is up, turn on an outside spigot with hose attached and 

run the water into a safe area where it will not disturb plants, lakes, streams or septic 

tanks. Run the water until there is no longer a chlorine odor. Turn the water off. 

Step 8

The system should now be disinfected, and you can now use the water. 

Step 9

Have your water tested for bacteria 7 to 10 days after disinfection. 

Materials Needed:

• One gallon of non-scented household liquid bleach; 

• rubber gloves; 

• eye protection; 

• old clothes; and 

• a funnel. 
Sampling and Testing the Well Water

Contact the local health department to have well 

water sampled and tested for contamination. Or, call 

your state laboratory certification officer to find a certified lab near you. You can get this number from the 

Safe Drinking Water Hotline (1-800-426-4791). 

If the health department issues sterile bottles for 

the private well owner to collect water samples, follow all instructions for the use of these bottles. 

After the pump is back in operation, the health department should sample and test the water at regular 

intervals.

CONCERNS AND ADVISORIES 

If in doubt about the well water supply, follow health department drinking and bathing advisories.

Remember that there is a danger of electrical shock from 

any electrical device that has been flooded; consult a certified electrician. Rubber boots and gloves are not adequate 

protection from electric shock. 

Well disinfection will not provide protection from 

pesticides, heavy metals and other types of non-biological 

contamination. If such contamination is suspected, due to 

the nearness of these contaminant sources, special treatment is required.

Information on home water treatment units (also called point-of-use and point-of-entry units) is available 

from U.S. EPA by phoning the Safe Drinking Water Hotline (1-800-426-4791). 

If you observe chemical containers (including barrels and drums) that have moved to your property, call your 

state or county health department or the Superfund Hotline (1-800-424-9346). 

For information on long-term water quality conditions in the area, consult the state or county health department. 

Well owners may have information about the construction, or testing of their well and this information will 

be helpful to the health department in determining water quality conditions. 

Septic systems should not be used immediately after floods. Drain fields will not work until underground 

water has receded. Septic lines may have broken during the flood. 

CAUTION: 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. 

It will be necessary to take long range precautions, including repeated testing, to protect the 

safety of drinking water.

OFFICE OF WATER (4606 M) www.epa.gov/safewater EPA 816-F-05-021 AUGUST 2005