Children Can Help Make Water Safer Using The Rays of the Sun

The disastrous floods in Mozambique, Malawi and Zimbabwe has brought to mind the SODIS method of treating small amounts of water for consumption at the family level. This is an activity that children can quickly learn and do and something practical they can do to help prevent sickness and even death from diseases like cholera.

SODIS is short for Solar Disinfection – water made drinkable using the rays of the sun.

It offers a household level solution to preventing diarrhoea and other waterborne illnesses. The method is simple and safe. It is suitable for treating small quantities of drinking water when the water supply has become unsafe for any reason. It needs sunshine to work properly.

Clean Drinking Water in 6 Hours

The SODIS method requires sunlight for 6 hours and PET bottles. PET is a type of plastic, most bottled water and sodas come in PET bottles.

The first thing to do is to ‘filter’ the water to make it as clear as possible, this can be done through a cloth. Then pour the clear but UNSAFE water into a PET bottle sized 2 litres OR LESS.

Lay the bottle in the sun for 6 HOURS or more. This can be on a corrugated roof. The UV-A rays in sunlight kill germs such as viruses, bacteria and parasites (giardia and cryptosporidia). The method also works when air and water temperatures are low.

The disadvantages are that:

  • The SODIS method does not make the water safer from any chemical pollution;
  • It depends on sunshine;
  • Only a small amount of water can be treated at a time and it can be time-consuming to cover the entire water needs of a household; and
  • It requires the availability of PET bottles.

What Can Children Do?

This is a practical and extremely useful activity that children can do and can manage. In a programme in Kenya, it was shown that children can help by collecting bottles, filtering the water through cloth and helping to ‘keep the time’.


Many scientific studies confirmed the effectiveness of the SODIS method. It kills germs in water very efficiently. The method has even been shown to improve the health of the population. Research into training strategies gave insight into which communication methods are most suitable. It has also been proven that the use of PET bottles in the SODIS method is harmless.  Here is a study from CORDIS.

Further Information and Practical Instructions

For more information download this PDF and technical paper from Practical Action.

Here is a YouTube video.

International Recognition for SODIS

The World Health Organisation (WHO), UNICEF, and the Red Cross, therefore, recommend the SODIS method as a way to treat drinking water in developing countries.

Solar disinfection is an example of another measure with proven health impact that requires little capital investment on the part of end-users, and is thus appropriate for the very poor.” WHO, 2007

UNICEF promotes a variety of treatment methods such as user-friendly filtration, simple solar water disinfection (SODIS) and home chlorination. These are all low-cost, effective and manageable at the household level.” UNICEF, 2009

Red Cross Prize, 2006: “The jury considers SODIS an impressive way of contributing by the simplest means to making water supplies better and safer, thereby reducing diarrhoea and other diseases like it, and mortality in developing countries.” Red Cross, 2006