Solar Water Purification

Solar Water Purification uses free energy from the sun, a water pasteurization indicator, a black pot or container, and a solar cooker. Water doesn’t have to boil to be safe to drink.

Water Pasteurization

WAPI - Water Pasteuriation Indicator

Disease causing organisms in water are killed by exposure to heat in a process called pasteurization. Water heated to 149° F (65° C) for a short period of time is free from microbes including E. coli, Rotaviruses, Giardia, and the Hepatitis A virus.


Since thermometers are not accessible to many people around the world, there is a need for a simple device that indicates when water has reached pasteurization temperatures.

Water Pastuerization Indicator in Black Bottle

The WAPI (Water Pasteurization Indicator) is a clear plastic tube partially filled with a soybean wax that melts at about 70°C (158°F). With the solid wax at the top end of the tube, the WAPI is placed in the bottom of a black container of water that is solar heated. Slide the WAPI to the end of the string so that the wax end is furthest from the washer

Water Pasteurization Indicator before and after pasteurization If the wax melts and falls to the bottom of the tube, it ensures that water pasteurization conditions have been reached. The WAPI has a stainless steel washer around it to keep it at the bottom of the container, which is the coolest location when solar heating water. Even if the water has cooled by the time you check it, as long as the wax is at the bottom of the WAPI then pasteurization has occurred.

Solar Water Purification

A solar cooker uses free energy from the sun and provides heat to pasteurize

Solar Cookit for Water Pasteurization

your water.

Orient the solar oven as you would for cooking and set the black pot or jar in the cooker. You can spray paint your pots or jars if they aren’t already black.

You can speed up the pasteurization process by placing the pot or jar inside a clear, heat-resistant plastic bag, but it’s often not necessary for pasteurizing.

In general face your cooker easterly in the morning and westerly in the afternoon.

Allow the water to cool before drinking. Keep pasteurized water covered until you use it to prevent recontamination.

Now you have safe drinking water!

Cooking with Solar Cookers
More information on Water Pasteurization
Return to Buy Water Purification Kits from Solar Water Purification

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