To pasteurize water, heat it in the solar box to at least 65 °C (149 °F) and keep the water at that temperature or above for at least 30 minutes. If no thermometer is available, heat until bubbles are rising from the bottom steadily. Natural waxes, such as beeswax, can be used to indicate pasteurization temperature. Also, you can use a WAPI device or the Boil 3, Add 1 Method.