A rather dangerous device used to fake water testing by unscrupulous door to door scammers pushing water filter systems. It simply rectifies the mains and passes DC current through water, causing rapid electrolysis that discolours the water strongly. I'm guessing that the unit is demonstrated with distilled water in one glass masquerading as "filtered water". The unit has a single pole switch (on the neutral core of the flex) so that the metal rods will be live at rectified mains voltage even when switched off on the unit depending on how the plug is wired (polarised plug) or inserted (two pin plug). This unit is only safe to touch if fully unplugged. In use the rods have full mains voltage between them, which could cause electrocution or burns if touched. Excellent. If you know someone with one of these devices, then make sure they know that it is a serious electric shock hazard. I don't recommend buying one of these, but if you feel the urge then the eBay keyword is "electrolyzer". If you enjoy the videos on this channel you can help support it with a dollar for coffee, cookies and dodgy electronic devices at https://www.patreon.com/bigclive