Consumers are being warned not to use household bleach containing fragrances or detergents to treat drinking water stored for emergencies.
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The Ministry of Civil Defence and Emergency Management has issued a warning that bleaches containing these additives shouldn't be used to disinfect drinking water as they can make people sick. But these bleaches are difficult to identify because cleaning product manufacturers aren't required to list ingredients.
All households are advised to store drinking water for use in emergencies. If you're storing tap water from a reticulated supply treated with chlorine, you don't normally need to add anything to the water. But if the water comes from an untreated source, health authorities advise adding a few drops of plain household bleach per litre of water.
Janola, one of the most well-known bleach brands, shouldn't be used. Manufacturer Pental Products told us all Janola liquid bleaches contain detergents and aren't suitable for treating drinking water.
Alternatives that manufacturers have advised can be used include:
Make sure you wash bottles for storing water thoroughly before use. Don't use plastic milk bottles as the milk protein can't be removed by washing and can cause bacterial growth. Fill each bottle until it overflows so no air is trapped. A supply of at least three litres per person per day for three days is recommended.
Label the bottle with a date showing when it was filled. The Ministry of Health advises water treated with bleach can be stored for 12 months. If you're storing tap water from a reticulated supply without adding bleach, replace it at least every 6 months. Store the bottles away from direct sunlight in a cool dark place.