Civil Defence logoTreating water in an emergency

This page has information on how to make water safe to drink in an emergency.

Drinking water that isn’t clean can make you very sick and even kill you.  You really don’t want to be sick on top of being involved in a disaster as well!

Treat any water that you are going to put in your mouth (including brushing your teeth), and the water you use to wash your hands.

Here are several ways you can make water safe to drink.



Boiling water is the easiest way to make water safe to drink.  It is the most effective way of killing micro-organisms including disease-causing bacteria, viruses, protozoans and parasites.

You don’t need any special equipment, training or chemicals.  All you need is a source of heat and something to heat your water in.

How long do I need to boil it for? 1, 5, or 10 minutes?

Zero minutes!

Water temperatures above 70° Celsius will kill pathogens within 30 minutes, and above 85° within a few minutes.  In the time it takes the water to reach boiling point at 100°, all the bugs which could make you sick will be killed.

If you haven’t got a thermometer to measure the temperature, all you need to do is get it to a rolling boil, and it will have been hot enough to destroy the organisms for quite some time.


Chemical treatment

Purification tablets

You can buy water purification tablets at all good camping stores.  Follow the instructions on the packets so you know how much water will be purified by each tablet.


Half a teaspoon of plain unscented household bleach can be added per 10 litres of clear water, and left for 30 to 60 minutes.  Do not use bleaches that contain added scent or perfume, surfactants or other additives - they can make people sick.

Examples of bleach you can purchase are:

  • Budget Bleach Regular
  • Budget Bleach Extra Strength
  • Clor-o-Gene bleach

These are sold at most New World and Pak'n Save supermarkets.

Budget Bleach Lemon should NOT be used because it contains lemon fragrance.


While this system isn’t the best way to make water safe, if you have no other options it is better than nothing. Once this system is up and running, remember to change the sand or dirt regularly.

  • Take a 20-30 litre bucket and drill or punch a series of small holes in the bottom.
  • Place several layers of cloth on the bottom of the bucket (this can be anything from denim to an old table cloth).
  • Add a thick layer of sand (preferred) or loose dirt. This will be the main filter, so it needs to fill at least half the bucket.
  • Add another few layers of cloth, weighted down with a few larger rocks.
  • Your home-made filter should be several centimetres below the top of the bucket.
  • Place another bucket under your filter bucket to catch the filtered water.
  • Pour the water into the top of your filter bucket. Gravity works to filter the water through the cloth and sand to drip out at the bottom into another bucket. If the water is cloudy or full of sediment, simply let it settle for a while and draw the cleaner water off the top.

Links to more emergency information

Porirua’s current emergency status - What's happening now? - The WREMO website for emergency updates and preparedness information

Wellington Region Emergency Management Office Facebook page – Learn how you and your family can get ready and get through – Get the latest information on civil defence emergencies in NZ – Find out about recent earthquakes in NZ – The latest on NZ weather

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