I read some info on the web that there is a reusable temperature sensor you can put in the water to determine if it has reached the temperature for pasteurization using a solar heating system.

It is some sort of wax in a glass container, and when it liquifies you have reached the temperature required. At that point, you leave the water in the sun for a specified time (I forgot how long.) and then it is safe to drink. You can then take the temperature sensor out and it will cool down and solidify until the next time you need it. The sensor eliminates the "by guess and by golly" method of determining proper time passage.

If anyone on the forum has tried it, I would be interested in knowing if it worked or if you ended up running for the throne.

Bountyhunter