Water treatment · Emergency
Bleach for emergency drinking water.
Drops of plain household bleach for a volume of water, using the US EPA dosing table.
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Bleach to Purify Water Calculator: how it works
The US EPA says to add 8 drops of 6% bleach, or 6 drops of 8.25% bleach, to each gallon of water, and 2 drops per quart or litre. Double the amount if the water is cloudy, colored or very cold. Stir, let stand 30 minutes, and the water should have a slight chlorine odour.
Worked example. 5 gallons of clear water with 6% bleach: 5 x 8 = 40 drops. The same 5 gallons with 8.25% bleach and cloudy water: 5 x 6 = 30 drops, doubled to 60. For 10 litres with either strength: 10 x 2 = 20 drops.
First choice is to boil. EPA's guidance is a rolling boil for at least one minute (three minutes above 5,000 feet / 1,000 metres), and to use bleach only if you cannot boil. If the water is cloudy, let it settle and filter it through a clean cloth, paper towel or coffee filter first. Use fresh liquid chlorine bleach, less than one year old when stored at room temperature, and a clean dropper.
Boiling or disinfecting does not remove heavy metals, salts or most other chemicals, per the US EPA.
Frequently asked questions
How many drops of bleach per gallon of water?
8 drops of 6% bleach or 6 drops of 8.25% bleach per US gallon, per the US EPA. Double for cloudy, colored or very cold water.
How long should I wait before drinking?
Stir and let it stand for 30 minutes. If there is no slight chlorine smell, repeat the dose and wait another 15 minutes.
What bleach can I use?
Regular unscented chlorine bleach labelled for disinfection and sanitization, with 6 or 8.25% sodium hypochlorite. Not scented, color-safe or bleach with added cleaners.
Can I treat any water with bleach?
The US EPA says not to use water with floating material in it or water that has a dark color or questionable odour.
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Not professional advice
Emergency use only, following the US EPA table. Bleach is hazardous; keep it away from children and never mix it with other cleaners. Not professional or medical advice. Follow your local health authority notices.