What are the risks?	How can I protect my family from contaminated water?	Is my water safe to drink after the flooding subsides?
How do I disinfect my well?	Is my well safe after disinfecting?	Links to more information.

	What are the risks?  High winds from hurricanes and tropical storms may cause electrical outages that shut down power to public and private drinking water systems.  But the primary health risk to drinking water is from the wide area flooding resulting from these storms.
Surface waters are susceptible to many sources of contamination.  During a flooding event, sewage runoff and overflow from lakes, rivers, and streams may be carrying bacteria such as E. coli and cholera, protozoa such as Giardia, and viruses such as hepatitis.
Public water systems may issue boil water notices if there are contamination risks from flooding, pressure drops, or line breaks until the water system and disinfecting equipment are back on line.  If there is a flooding event in your area, your county health department will issue a precautionary boil water notice through your local television, radio, and newspapers.
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How can I protect my family from contaminated well water? If flood waters have reached your well, or if you notice any change in the appearance or taste of your water, or even if you are unsure about the impact of flooding on the water quality in your area, you should boil all of the water you use for drinking, making beverages, cooking, brushing your teeth, washing dishes, and washing areas of the skin that have been cut or injured (Be sure to cool the water first.)  The water should be brought for a rolling boil for at least one minute.  Aerating the water by pouring it several times from one container to another will help to dispel the flat taste of boiled water.
Boiling water is the most effective method for killing disease-causing microorganisms.  But chlorine and iodine are good alternatives.  Common, liquid household bleach can be used to disinfect water.  Do not use scented or color-safe bleaches or those with added cleaners. It is also the best method to disinfect your well after the flooding has subsided.  If the water is cloudy, filter it first.   Check the percentage of available chlorine on the bleach container and use the table below as a disinfecting guide.

Available Chlorine	Drops/Quart of Clear Water
1%	10
4-6%	2
7-10%	1
Unknown	10

Mix the treated water thoroughly and allow to stand for 30 minutes.  The water should have a slight chlorine odor.  If it does not, then repeat the disinfecting process.  To reduce the chlorine taste, aerate the water by pouring it from one container to another several times.

Chlorine and iodine tablets are generally sold in drug and sporting goods stores.  Follow the directions on the label for water disinfecting.

Bottled water may also be used as alternative to disinfecting.  Also, none of the disinfecting methods will remove chemical contaminants.  If this is a concern because of a spill or accident, drink only bottled water.  The  National Center for Environmental Health recommends stocking one gallon of bottled water per person per day for three to five days.

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Is my water safe to drink after the flooding subsides? 

No -- If your well has been flooded, you must first disinfect it and contact your county health department for information on how to sample your water and where to bring the sample for bacteriological testing.

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How do I disinfect my well? 

It is important to disinfect both the well and all of the household plumbing to assure that all infectious agents are killed. If you have water treatment devices, replace all membranes, cartridges, and filters. Water softeners and water heaters should also receive special attention to ensured that they do not reintroduce bacteria into your plumbing system.

Both amount of chlorine and the length of time you allow it to remain in your system are important considerations. Common unscented laundry bleach can be used effectively as a chlorine disinfectant. Follow these steps:

1. If the water is discolored, run the water until it is clear.

2. Turn off and then drain your hot water heater.  Chlorine bleach is not as effective in water above 105 degrees.

3. Bleed the air from pressure tanks so that chlorinated water can completely fill and sanitize them. Water softeners, sand filters, and iron removal filters should be backwashed with chlorinated water.   Remove and replace charcoal filters after the chlorinating process is completed.

4. To avoid adding further contamination to the well during the disinfecting procedure, first clean up the work area around the top of the well. Remove grease, mineral deposits, and other encrustation from accessible parts of well interior and flush these surfaces with 1/2 cup of laundry bleach in 5 gallons of water.  Determine if you have an aboveground or submersible pump.

a. If you have an aboveground pump...

• Turn off the well pump and run the water until there is no pressure

• Remove the pump from the well casing adapter

• Once opened, some above ground pumps require replacement parts such as gaskets to reseal the system.  Some may also require priming to rebuild the pressure in the pump.  If you have questions, contact your county health department, water management district, or a licensed well driller.

• Consult the table and pour in the recommended amount of bleach solution.   Try to coat the sides of the casing as you pour.  If you get chlorine on the pump or wiring, flush it thoroughly with fresh water to prevent later corrosion.

b. If you have a submersible pump...

• Pour in the quantity of bleach recommended in the table into the top of the well.

5. Re-cap or plug the well opening and wait 30 minutes.

6. Turn on and, if needed, re-prime the pump. Open all of the faucets on the system one by one. Allow the water to run until there is a noticeable smell of chlorine. You may also want to flush the toilets. If you have outside faucets, you may want to direct the water away from sensitive plants. If you cannot detect a chlorine odor, re-chlorinate the system.

7. Turn off all of the faucets and allow the chlorine to remain in the system for at least eight-hours, preferably 10-12 hours.

8. Again open all of the faucets and run the water until there is no chlorine smell.

Bleach Disinfecting Table

This table is a guide for the amount of chlorine bleach to use for well and plumbing system disinfecting. Do not use scented bleach or bleaches containing other additives. Your county health department may provide additional information for your area.

The bleach should be diluted with 10 parts water. For example, dilute 1 cup of bleach with 10 cups of water before pouring it into your well.

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Is my well safe after disinfecting? 

Although chlorine bleach is generally effective against microorganisms, the only way to verify that the water is safe to drink is to have it tested. Also, chlorine bleach will not remove chemical contamination that may have gotten into your well. Consult with your county health department to determine if other sampling is appropriate for your area and for instructions on getting your water tested.

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Links to more information

You may also want to check out Department of Health Emergency Operations  on the Dropdown menu above and these Internet sites: (all open in a new window)

National Weather Service

Hurricane Center, Miami

American Red Cross

Centers for Disease Control

US Environmental Protection Agency

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