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WATER PUMPS, TANKS, TESTS, WELLS, REPAIRS
WATER CONSERVATION MEASURES
WATER CONTAMINANT LEVELS
WATER FILTERS, HOME USE
WATER HAMMER NOISE DIAGNOSE & CURE
WATER ODORS, CAUSE CURE
WATER PUMP REPAIR GUIDE
WATER PRESSURE LOSS DIAGNOSIS & REPAIR
WATER PUMP SHORT CYCLING
WATER SOFTENERS & CONDITIONERS
WATER TANK REPAIR PROCEDURES
WATER TANK: USES, TROUBLESHOOTING
WATER TESTS, CONTAMINANTS, TREATMENT
WATER TREATMENT EQUIPMENT CHOICES
WELLS CISTERNS & SPRINGS
WELL CHLORINATION & DISINFECTION
WELL FLOW RATE
WELL WATER PRESSURE DIAGNOSIS
WELL YIELD IMPROVEMENT
WINTERIZE A BUILDING
This article describes how to use household bleach or bleach of other strengths to disinfect water for emergency drinking water use. We also explain how people deal with the risk of Cryptosporidium in drinking water. This article series outlines methods to purify or sanitize drinking water in an emergency following a disaster such as an earthquake, flood, or hurricane.
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Chlorine bleach (sodium hypochlorite) Iodine alternatives for disinfectants include chlorine-based products (bleach) and non-iodine-based water filters. Commercial bleach such as laundry bleach purchased at a supermarket contain 3 to 6% sodium hypochlorite. Be sure that bleach to be used to purify drinking water contains only sodium hypochlorite. For example, do not use a bleach-soap mixture.
How much bleach do we need to purify drinking water? It depends on the concentration (strength) of the bleach solution you're using as well as the condition of the water. If you don't know your store-bought household bleach solution strength, use 10 drops per gallon of water and let the solution stand for 30 minutes. If after 30 minutes there is absolutely no chlorine or "bleach" smell in the water, repeat the dose and let the solution stand for another 30 minutes.
In our detailed drinking water chlorination procedure article found at DISINFECTANT Quantity to Use in Water we review the amount of bleach or other disinfectants needed in more detail and we describe the U.S. EPA's advice for superchlorination of drinking water.
Watch out: Chlorine does kill Giardia cysts if used in high enough concentration and for sufficient contact time, but typically the chlorine concentration in water necessary for Giardia would be too high for drinking purposes. And at WATER DISINFECTION LIMITATIONS we report that relying on disinfectant to kill Cryptosporidium cysts is a mistake.
The chlorine concentration that one would find in a swimming pool, levels of chlorine not suitable for drinking water consumption would require about 20 minutes to kill a Giardia cyst.
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For this reason some municipalities where Cryptosporidium cysts are a concern add a water treatment step using chlorine dioxide. Others may use a combination of UV light and chlorine in the water treatment procedure. This treatment is also available to hikers, travelers, and for emergency water supply use.
How to Remove the Bleach Odor from Disinfected Water
Do not attempt to remove the chlorine or iodine taste from water until the water has completed its treatment wait period.
Boil the water for a few minutes. Heat will speed the decomposition of the bleach in the water. If you have no heat source let the water stand open for a few hours.
Pour the water back and forth between clean containers - the aeration process will speed the release of the chlorine odor and taste from the water. Iodine treated water won't have such a strong taste but you can improve the taste of treated water further with a small pinch of salt or by mixing in a drink powder like lemonade.
Add vitamin C to the water, or a drink that contains vitamin C.
Watch out: for these limitations on the effectiveness of bleach or chlorine disinfection of drinking water or grey water:
This discussion has been moved to a separate article: VEGETABLE DISINFECTION or select a topic from the More Reading links shown below.
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