On average it takes about 30 seconds for hot water to reach the shower, so for 30 secs water is being wasted. I know running water for 30 seconds doesn't seem that bad but there are a lot of water shortages and droughts going on all around the world. I know its possible to heat water with 9v battery. Question is How does it work ? What are the process involved ? I want to heat the water during those 30 second until the hot water kicks in.