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

The reusable, durable WAPI is a simple device containing a special wax that helps users determine when water has reached pasteurization temperatures. The WAPI can be used for pasteurizing over most fuel sources — including wood, charcoal and gas — but it works particularly well in conjunction with a solar cooker. Great for camping and emergencies.