Floods and Health - advice from Manatū Hauora Ministry of Health

Floodwaters can carry bugs that cause disease from the ground surface, septic tanks and sewerage systems.

Information supplied by Manatū Hauora Ministry of Health  Photo Credit 1News

During flooding, listen to your local radio stations for civil defence advice and follow instructions.

Afterwards, it’s important to make sure your food and water aren’t contaminated, and to clean up, drain and dry out the house as quickly as possible.

Food safety after a flood

Salvaging food items and utensils

Floodwaters can carry bugs that that can contaminate food.

• Wash cooking, eating, and any other kitchen utensils that have been covered by floodwater in hot soapy water. Rinse thoroughly in safe water, then disinfect by immersing for 1 minute in a solution of 500 ml (about 2 cups) of plain, unperfumed household bleach in 10 litres of water. Rinse again in safe water. Alternatively, boil all utensils for 1 minute and let cool.
• Destroy all unpackaged food and food items packed in paper, cardboard or non-waterproof material that have been exposed directly to the floodwater.
• Get rid of all foods needing refrigeration when they have been unrefrigerated for more than 2 hours.
• If the power has been off to the freezer for more than 2 days, get rid of all thawed food.
• Save foods in waterproof, airtight containers (eg, tins) that have been in floodwater, but make sure they are thoroughly cleaned before opening by:
  • washing and scrubbing in warm water that contains soap or detergent, then rinsing in clean water
  • soaking for at least 1 minute in a solution of 500 ml (2 cups) of plain, unperfumed household bleach mixed with 10 litres of water, then rinsing in clean water from a safe supply.
• Write on the contents of tins if labels are damaged so that you know what is inside them.
• Wash and disinfect your can opener before using.
• Throw out the contents of bottles with crown tops and crimped or screw caps if water rose above the neck of the bottle. It is safer to get rid of all home preserves, as these are a higher risk than commercial items.
• Do not use packaged or canned food if it has been punctured or is bulging or leaking or the top has popped up. Throw out any canned foods dented on the side or along the top or bottom seams.
• Cook all food thoroughly and eat immediately. Cook only enough for each meal. Do not save leftovers.
• If in doubt, throw out!

Gathering food

• Do not eat garden produce if the soil has been flooded. Clean up and remove debris and sprinkle gardens with lime.
• Do not eat shellfish from the river mouth or harbour after a flood.

Water safety after a flood

• Flush your water pipes, if on town supply, by turning the taps on and running until the water is clear.
• If your water tank is affected by floodwater, get rid of the water (it may be polluted), clean the tank out and disinfect it. Boil water before drinking.
• If you use bore water that may have been affected, pump the bore to waste for 24 hours. If the bore is under water, do not pump.
• If your water comes from a well that may have been affected, mix 2.5 litres of plain, unperfumed household bleach with 45 litres of water and pour down the well. Replace the well cover and turn on each tap until there is a smell of chlorine in the water. Turn off the tap, but do not use the water for 8 hours. Then open all taps and flush out the chlorine.

Restoring a house after flood damage

Soon after heavy rains have stopped and waters have drained off the ground surface, sewers will generally return to normal function. It is important to clean up, drain and dry out the house as quickly as possible.

• Take photos of the damage before starting the clean-up.
• Take out everything that is wet and that can be moved – floor coverings, furniture, bedding, clothing, etc, and put them outside to dry when the weather is fine.
• Get rid of mattresses and other large items that have been soaked with floodwater. Foam rubber mattress or pillows may be able to be washed, disinfected and dried in the open air.
• Get rid of contaminated clothing, carpets, upholstered furniture, toys and bedding unless they can be cleaned and disinfected.
• Check for trapped water and mud in wall cavities, as well as under shower trays, baths, benches and bottom shelves. You may have to chisel out some bricks at the bottom of brick veneer walls.
• Remove skirting, if necessary, and cut out softened plaster board in damaged areas. (Consult an expert such as an insurance assessor or builder.)
• Use heaters (eg, hot air blowers for under-floor space), but open all doors and windows.
• Replace wall linings, floor coverings, etc, only after things have dried out.
• Leave redecorating for at least 3 months after finishing the repairs to prevent risk of mould, blistering and peeling.
• Do not light fires in brick fireplaces for at least 2 weeks, and then use only small fires until the firebricks have dried out.
• Consult an engineer if there are signs that the house has moved on its foundations, eg, buckled floors, new cracks in walls, out of shape door frames.

Cleaning out a basement after flooding

• Check all floor drains in the basement to see that they are clear of debris and drain away water under the house. Try to increase the airflow to speed drying.
• Drain any surface pools by pumping or bailing.
• Wash or flush down walls, shelves and floors with clear water and sweep to remove contaminated water and sediment.
• Use a solution of 1 litre of household bleach in 10 litres of water to rinse down walls, floors and other equipment. Leave on for 30 minutes before rinsing with clear water. Keep windows open during this treatment.
• Use plenty of hot water and soap or dishwashing detergent for the final clean-up of walls, floors, cupboards etc.
• Ventilate area by opening all windows or use fans, if power is available.
• Use a commercial deodoriser, if necessary, to remove any remaining smells.

Related websites:

Auckland Regional Public Health Service – Flooding  Advice on staying safe during and after a flood.

National Emergency Management Agency The agency responsible for emergency management in New Zealand.

Get Ready  A Civil Defence website with advice for the public on preparing for natural disasters.

Protecting your health in an emergency