Drinking Water Safety Guide to Use During & After a Flood

Enduring a flood from a natural disaster is devastating to your family and your property. Whether you’re the victim of a flood caused a flash downpour, hurricane, earthquake, or tsunami, your top concern during and after the storm is the health and safety of your loved ones — which needs to include your drinking water.

When there’s heavy rainfall, the water you use for everyday activities becomes a threat to your health. Bacteria, viruses, parasites, and chemicals can leach into potable water from overflowing sewage systems, leaked industrial chemicals, and run-off agricultural chemicals. It’s not just drinking contaminated water that’s dangerous, either. Unpurified water that gets into the body in other ways can be harmful or even toxic. For example, treating a wound with bacteria-filled water can cause infection, and eating food that’s been washed with it can lead to waterborne illness.

While your local health department will put out public advisories (called boil orders) if your area’s water has been compromised, there may be cases where you’re unable to receive local safety notifications. If there is a power outage and you don’t have a battery-powered radio in your disaster preparedness kit, for instance, it’s important to know how to safely use water during and after a flood until you know it’s safe to use.

Our guide will help you identify when your water is at risk of contamination as well as how to treat it to make it safer for drinking and hygiene, but it’s not a substitute for orders from your local health department. Be sure to follow all government orders in the event of a flood.

Important information about well water

Even if you use a private well rather than city water, your supply may still be harboring pollutants. Unfortunately, well water is at high risk of contamination, especially if it’s a shallow reservoir. If your well is surrounded by standing water post-flood, especially after floodwaters have started to wane in other areas, it’s a good indication that the water inside is unsafe.

There are conflicting opinions on using well water during and after a flood. Some health experts say you can use it as long as you treat it before use, but others strictly advise against it. Your local health department will likely put out an advisory for well-water users in the event of a flood. Opt for bottled water if possible, but if you do use well water, be sure to treat it first by following the instructions below.

Treating water for safe use

Treating your water may kill the bacteria, viruses, and parasites that entered it during or after the storm. However, not every method will kill every organism, and it’s difficult to remove chemical contamination from water post-flood. Reverse osmosis is a reliable, relatively affordable water treatment and purification system that removes some of the chemicals often found in tap water, but even it doesn’t remove 100% of them. If you know there is a risk of chemical contamination, it’s safest to rely on bottled water.

For non-chemical contaminants, you can use one of three methods of treating water: boiling, purifying, and filtering. Follow your local health department’s guidelines on which methods of water treatment will make your water safe to use. Be sure to use sanitized containers that haven’t been exposed to floodwater to store your treated water.

Boiling

If your water is cloudy, you’ll need to separate the polluted particles from the water before boiling it. You can filter it through a fabric or paper cloth or a coffee filter, or you can let it sit undisturbed until the particles separate completely from the water. If you choose to let it sit, remove just the clean water from the sifted-out material so you can treat it on its own. (Try using a ladle or a small drinking glass to scoop out the water carefully.) Then, follow these steps:

Bring water to a rolling boil for 3 minutes, then remove it from the heat.
Allow it to cool completely, no matter how you plan to use it. (Drinking water that’s too hot can scald your mouth and throat, and letting it touch your skin can scorch it.)
Put the water in a sanitized container and seal it.

If you can’t find a container you’re sure hasn’t come into contact with floodwater, you can keep it in the pot you boiled it in and cover it securely.

Purifying

For this method, you can use chlorine bleach, chlorine dioxide tablets, or iodine. For chlorine-based solutions, opt for an unscented option, which will help ensure the smell and taste of your water isn’t off-putting. Some people are allergic to iodine, so do not use this method unless you know for sure that everyone who will use the water doesn’t have an allergy to it. Follow these steps based on the purifying method you choose:

If your water is cloudy, you’ll need to separate the polluting particles from the water before boiling it. You can filter it through a fabric or paper cloth or a coffee filter, or you can let it sit undisturbed until the particles separate completely from the water. If you choose to let it sit, remove just the clean water from the sifted-out material so you can treat it on its own. (Try using a ladle or a small drinking glass to scoop out the water carefully.)

Chlorine bleach

Put the water in a sanitized container.
Add slightly less bleach than indicated on the product label’s dilution directions.
Mix.
Let it stand for at least 30 minutes, no matter how you plan on using it. If the water is still cloudy, add a few extra drops of bleach (not exceeding the amount directed on the product label), mix, and let sit for another 30 minutes.
Seal the container.

Chlorine dioxide tablets

Put the water in a sanitized container.
Add tablets based on the product label’s dilution directions.
Allow the tablets to dissolve, and then mix.
Let the water stand for at least 30 minutes, no matter how you plan on using it.
Seal the container.

Iodine

Put the water in a sanitized container.
Add iodine based on the product label’s dilution directions.
If you’re using liquid iodine, mix the solution. If you’re using tablets, wait for them to dissolve before mixing.
Let it stand for 30 minutes or according to the product label’s directions.
Seal the container.

Filtering

Use a sanitized container and a filter with the smallest pore size possible.
Follow the product label’s filtering directions.
Add chlorine bleach, a chlorine dioxide tablet(s), or iodine to the filtered water. (See the above instructions for adding a purifying chemical.)
Seal the container.

Alternative clean water sources

There are a few potential sources of clean water in and around your home. However, you still have to treat it, and it’s best to use it only for hygiene rather than consumption. Don’t use or drink any water that you even suspect has been contaminated or come into contact with floodwater. If it smells bad or looks unclean (it’s cloudy, colored, or has visible particles, for example), don’t use it or drink it.

You may be able to use:

Water in your drinking water heating tank (not your home heating system’s water tank)
Melted ice cubes that were made before the contamination risk and were safe from floodwater
Fresh rainwater captured by a vessel you know hasn’t been contaminated, such as a rain barrel
Moving bodies of natural water, like rivers and streams

After water restrictions are lifted

Unfortunately, even when the health department ends boil orders, you can’t go back to using your water normally without taking a few actions. Even though you’ll already be dealing with flood damage repair and cleanup tasks, make sure addressing your home’s water supply is one of the home projects you address immediately after a flood.

Follow these steps to start using your water again after a flood.

First, flush your home’s pipes by:

Continuously running hot water taps that aren’t connected to appliances (including all your sinks, bathtubs, and showers) for 15 minutes.
Flushing each toilet at least once.
Flushing cold-water taps (including utility sinks and refrigerator lines for water and ice) for five minutes.
Flushing all remaining taps for five minutes (including your remaining appliances — such as the dishwasher and washing machine — and your outdoor spigots).
Replacing all your water filters and cleaning all your faucets.
Running the dishwasher cycle once while it’s empty.
Running the washing machine cycle once while it’s empty.

Note that there may be a lingering odor and/or discoloration in your water for a day or two. This is normal, and the water should still be safe to use. If these issues last for more than a few days, notify your water supplier and the health department to learn what safety actions to take next.

Next, sanitize belongings and surfaces that come into contact with food and drinking water:

Sanitizedishes, cutting boards, silverware, and pets’ food and water dishes in the dishwasher. Items that can’t go in the dishwasher should be sanitized with hot, soapy water and air-dried.
Sanitizesurfaces that may come into contact with your food (counters, stovetops, pantry and refrigerator shelves, etc.) using a bleach-based cleaner.
Discardice that was made during and after the flood. Make another batch of ice, and discard it. Sanitize the ice containers in the dishwasher. Once you’ve taken these steps, any new ice you make should be safe to consume.

If you have a well:

You’ll need to test your well water and inspect the well itself for cracks and damage after a flood. Your local health department will provide you with a testing kit or send a professional to run necessary tests and collect a water sample, which will be sent to a lab for safety analysis.

Before you test it, you’ll need to shock the well water, which is usually done with chlorine. Your health department will provide you with instructions on how to do this so you can submit an accurate sample for testing. They will also advise you if additional samples are needed. In some areas, multiple samples, taken a week or so apart, are required even if your initial samples pass safety tests. If your structure was damaged during the storm, call a well specialist to repair cracked or broken stonework or to replace the well pump.

Other floodwater safety concerns

Even if you’re not actually drinking it, do not use water you suspect is contaminated in these ways, since these actions may lead to ingesting it:

Preparing and cooking food
Washing produce, meat, or food storage containers (including cans and plastic bags)
Making ice
Making baby formula
Brushing your teeth
Washing your hands or bathing
Washing dishes
Washing clothing

Additionally, take these floodwater safety precautions:

Infants, senior citizens, ill individuals, and pets may be more sensitive to contracting an illness from floodwater, even if it’s been treated. Prioritize bottled water for their use as much as possible.
Even if you clean produce with treated water, consider cooking it to kill as many contaminants as possible.
Do not make ice cubes using water that may be contaminated. Freezing water doesn’t make it safe for consumption.
Use hand sanitizer and cleansing wipes instead of water for washing your hands and bathing as much as possible. Clean water will be scarce, so reserve it for drinking and hygiene.
If you use your shower, keep your mouth and eyes closed when they come into contact with the running water.
Take precautions to prevent injury. Broken skin exposed to dirty water can lead to serious infections.
Use bug repellent as necessary, because bug bites and stings can lead to broken skin.
Throw out wooden cutting boards and dishes that have come into contact with floodwater. (Wood is porous and may absorb pollutants.)
Throw out baby bottle nipples and pacifiers that may be compromised.
Throw out food that may have come into contact with floodwater.
Don’t take any chances with food, dishes, or containers — when in doubt, toss it out.

Finally, know the warning signs that someone has been exposed to contaminants. Seek treatment as soon as possible if any people or pets experience these after drinking or using floodwater, even if it was treated. Keep an eye out for:

Cramping
Diarrhea
Dizziness
Extreme fatigue
Fever
Vomiting
Weakness

If you live in a storm-prone area, prepare for a flood as much as possible. Keep plenty of bottled water on hand during storm season, even before there’s a looming disaster. Improve your odds of having clean water in an emergency. Install a water treatment system by hiring a water treatment service. You’ll still need to put safety first when it comes to water usage, but you may have access to clean water longer after the rain starts pouring and more quickly after the floodwaters start to subside.

It’s better to be safe than sorry when it comes to drinking water safety during and after a flood. Use extreme caution, follow health department warnings and advisories, and always err on the side of safety.

Drinking Water Safety Guide to Use During & After a Flood

Important information about well water