[controversial97]

It appears that this system turns tapwater into hydrogen and oxygen by electrolysis.

I'm not a chemist, but I messed around with electrolysis decades ago when I was a teen who was into chemistry sets.

I am not convinced that tapwater is anywhere near pure enough that this system can work without frequently changing electrodes and removing gunge, even with some filtering.

Electrolysis does not just split the water molecules, there is a chemical reaction with whatever else is dissolved in the water.

[theincredulousk]

Good intuition about the importance of pure water. In professional engineering, filtering water is a sufficiently solved problem. Even for consumer use, you can buy multi-stage filters for home use that perform well enough to make water taste "bad" because it is so pure.

It would likely require periodic replacement, proportional to use, of relatively expensive filter(s) - not regularly changing electrodes or invasive deep cleaning.

[controversial97]

What would you make the electrodes out of?

Copper will react with the chlorine in tapwater and make an insoluble green scum of copper chloride.

Electrolysis with stainless steel makes highly toxic hexavalent chromium.

Platinum is astoundingly expensive, even for plating.

How expensive a filter is needed to remove 99.999% of the chlorine?

The thing with electrodes is that a fiftieth of a millimeter of non-condutive crap on the surface hugely reduces the effectiveness. Around here the bottom third of my kettle has a tenth of a mil of limescale.

[theincredulousk]

even type II water, which is a standard output of off-the-shelf lab water filtration systems, only has <= 5 ug/L of chlorides, sodium, silica.

And Platinum is like $30 a gram. There is 1/5th of a gram of Gold in a standard desktop computer and Gold is twice as expensive as Platinum.