Post #KeralaFloods Rehabilitation: Making Water Safe for Drinking After a Flood

Dr Roshan Radhakrishnan
The worst of the Kerala floods is over, leaving the state devastated in a manner not seen in nearly a century. The loss across most districts of God's Own Country runs into thousands of crores financially and perhaps a lot more, emotionally and psychologically.

But now is not the time to rest. Because, as the floods finally retreat, it is now time to rebuild. It is time to undo the damage.

Understanding that this is a vast topic, I am posting a series of articles here specific to various aspects of flood relief. I have been aided in this by my dear friend and classmate of old, Dr Reshma, a specialist in Community Medicine alongside guidance notes provided by the Directorate of Health Sciences, Kerala.

The topic in this post is:

Making Water Safe for Drinking After A Flood

We will tackle this topic in two steps:
A - Superchlorination of wells / tank water / underground sumps.
B - Measures for safe drinking water.

A. Superchlorination

Use well / tank water only after superchlorination. So how do we do it?

  • Take 5 gms bleaching powder for every 1000 litres of water in the well (one ring of a well can hold 1000 litres, while in wells of small diameter, a ring can hold 250 litres).
  • Make a paste with bleaching powder and a little well water.
  • Then fill this bucket up ¾ with well water.
  • Stir. Let it rest for 10 minutes.
  • Transfer the supernatant liquid into another bucket which is then lowered into the well.
  • Agitate the water to allow for proper mixing.
The well water can be used after an hour.
Repeat this process twice a week.

Post flood relief in Kerala: The steps for Making Water Safe for Drinking After A Flood - Superchlorination -
The steps are also compiled in this easy-to-save image which can be pinned or saved for future use.


Methods for water chlorination:


1. 1 chlorine tablet (500 mg) for 20 litres water.
2. 12.5 gm tablet for 500 litres of water.
3. 25 gm tablet for 1000 litres water.


20 ml liquid chlorine for 1000 litres water (ideal for liquid chlorine to be used under strict supervision of trained health staff.)

DO boil water for 20 minutes before consumption, even though the water has been chlorinated.

SAFETY FOR DRINKING WATER / WASHING WATER  Methods for water chlorination

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