We tested the difference of hydrogen generation by Pocket.

Left “Pocket” bottle is generated by Tap water. right one is generated by Evian (TDS 304ppm, hardwater)
Please see the following youtube movie.
Hard water looks releasing a lot of fine bubbles. The water is whitish by fine bubbles, comparing to Tap water one.

Generally higher TDS water generates more hydrogen than lower one. Meanwhile electric consumption is considered to be worse.
Most of bottled water shows TDS or hardness on their label. If you use bottled mineral water for Pocket, please choose the best one for your generation. If you prefer higher density, high TDS water is suitable for you.