Two separate tanks are necessary. One for the input water and one for the treated water.
It is important, that the water is clear and not chemically contaminated. A piece of fabric can be used to filter the water to a small degree.
There should always be water in the input tank, because the device can get very hot without water. To stop the device the absorber just has to be covered.
The water should be used within a day.
In the evening or at the next morning the input tank is filled again or the absorber is covered to deactivate the device.