[BlackNight666]

I read that the electric water ionizers that claim to have a health benefit, produce the alkaline water by siphoning the water from the cathode during the electrolysis of water in the machine. Since electrolysis of water preferentially discharges H2O, does it mean that looping the machine on itself will eventually produce pure D2O?

[Borek]

Yes and no.

In principle you can definitely enrich water in D₂O this way. In reality you will hit some obstacles sooner or later. Plus, the process is painfully slow.