Make Water Safe to drink
99
How much chlorine to use?
The amount of chlorine needed to disinfect water depends on how contaminated
the water is (how many and what kinds of germs it contains). The more germs
there are in the water, the more chlorine you need to get rid of them. It is
important to add enough chlorine so that some is left in the water after the
germs are killed. The chlorine that is left is called free chlorine. This will kill
any new germs that get into the water. If the water has free chlorine in it, it
will smell and taste just slightly of chlorine. This tells you it is safe to drink. If it
has too much, the smell and taste will be strong and unpleasant.
To use the right amount of chlorine, you need to know how strong your
chlorine solution is. Chlorine comes in different forms — gas, bleaching powder,
high-test hypochlorite (HTH), and household liquid bleach. But household bleach
is the form of chlorine that is easiest to find.
Household bleach may have different amounts of chlorine. Most common
are 3.5% and 5%. This book shows how to disinfect water with 5% chlorine
household bleach. Read the label to see what percent of chlorine is in your
bleach. If it is less than 5%, you will need to add more bleach to the water.
If there is a lot of solid matter in the water, the chlorine will not work as
well, so filter the water or let the water settle. Pour the clear water off into a
clean container and then add chlorine. If you cannot filter the water or the
water is cloudy, use twice as much bleach as what is shown in the chart below.
Water
For 1 liter or
1 quart
5% Chlorine Bleach
2 drops
For 1 gallon or
4 liters
8 drops
For 5 gallons or
20 liters
1/2 teaspoon
For a 200 liter
barrel
5 teaspoons
Add these amounts of bleach to filtered or settled water and wait at least 30 minutes
before drinking. If the water smells and tastes just slightly of chlorine, it is safe to
drink. If you do not have a dropper, you can dip the spoon in the bleach and let the
drops fall one by one off the side of the spoon.
A Community Guide to Environmental Health 2012