The idea is simple. What would be the easiest way to preserve water during a shower? I don’t think it will be by waiting for a complex invention to be installed. The simplest solution I could think of was to use a plastic PET bottle.
Just drill some holes in the bottle cap and fill it up with water. A very simple solution. Just press the bottle to squeeze out the water to rinse yourself.
I managed to take a shower with little less than 1.5 liters of water.
Just make sure you clearly mark the bottle for showers only.