Make Drinking Water Safe with Bleach

Last updated on January 31st, 2019


Water. We can’t live without it. Not for long – only about 3 days. In fact, water is the one thing that we need the most, to survive.

The general rule for storing water for an emergency or disaster is 1 gallon per person per day.

There are variations to this generality, ranging from a half gallon to as much as 3 gallons per person per day because there are other uses for water besides just drinking.


A problem that you will encounter during an emergency or disaster is not only obtaining water to drink, but treating it to make the water safe to drink.

The best way to treat water for drinking is to boil it first, for one minute.

According to the Wilderness Medical Society, water temperatures above 160° F (70° C) kill all pathogens within 30 minutes and above 185° F (85° C) within a few minutes. So in the time it takes for the water to reach the boiling point (212° F or 100° C) from 160° F (70° C), all pathogens will be eliminated, even at high altitude.


If boiling is not possible, another effective way to make water safe to drink is to add a specific amount of regular household bleach. Depending on brand or concentration, regular household bleach contains between 5.25 and 8.25 percent available chlorine (liquid sodium hypochlorite), which will disinfect the water if added in the right amount.




How to purify water with Bleach

If the collected water to be treated is cloudy and contains sediment, either scoop a new sample with less sediment, or strain it first through a makeshift filter (cloth bandana, t-shirt, coffee filter, etc..) or let it sit in the container allowing sediment to settle to the bottom. Gently pour off the clearer water on top.

Use regular liquid household bleach (any brand); however the only active ingredient should be sodium hypochlorite. Do not use bleach that contain soaps, perfumes, or dyes. Be sure to read the label.

Add 8 drops (almost one-eighth U.S. teaspoon) of regular liquid bleach per one gallon of water to be treated.

Mix thoroughly and let stand for 30 minutes (important).

Then, smell the water. If the water has a faint smell of chlorine, then it is okay to use. If you cannot detect any chlorine odor, add another 8 drops of regular liquid bleach. Let stand, and smell it again. If you still cannot smell chlorine, discard it and find another water source.

Chlorine test strips are useful to verify the chlorine level in the water. The maximum safe level for drinking water according to the EPA is 4 ppm (parts per million).

Note that bleach has a shelf life, although you will probably not see a date on the bottle. Chlorine bleach may lose 20% to as much as 50% effectiveness within a year, so be sure to date your bottle upon purchase.


Notes about chlorine level for safe drinking water

The EPA recommends a maximum (no more than) 4 ppm (parts per million) of chlorine for safe drinking water.

A typical municipal water supply measured at the home faucet is typically between 0.2 and 0.5 ppm chlorine.

It takes 45 minutes to destroy Giardia Protozoan (common cause of diarrhea) with 1 ppm chlorine level.


‘CDC’ instructions for safe drinking water with bleach:

From the CDC, Centers for Disease Control, “If you don’t have clean, safe, bottled water and if boiling is not possible, you often can make water safer to drink by using a disinfectant, such as unscented household chlorine bleach”

Add 1/8 teaspoon (or 8 drops; about 0.625 milliliters) of unscented liquid household chlorine (5–6%) bleach for each gallon of clear water (or 2 drops of bleach for each liter or each quart of clear water).

Add 1/4 teaspoon (or 16 drops; about 1.50 milliliters) of bleach for each gallon of cloudy water (or 4 drops of bleach for each liter or each quart of cloudy water).

Stir the mixture well.
Let it stand for 30 minutes or longer before you use it.
Store the disinfected water in clean, disinfected containers with tight covers.


‘WHO’ instructions for safe drinking water with bleach:

From the WHO, World Health Organization, “Chlorine is commonly available to households as liquid bleach (sodium hypochlorite), usually with a chlorine concentration of 1%”

Disinfection with chlorine is the most appropriate way of ensuring microbiological safety in most low-cost settings.

At least 30 minutes contact time should be allowed after the chlorine is added to the water before the water is drunk, to ensure adequate disinfection. The free chlorine residual (the free form of chlorine remaining in the water after the contact time) should be between 0.5 and 1.0 mg/l (0.5 ppm and 1.0 ppm).

Related article: Bleach – Water Ratio For Drinking Water


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