Electrolysis video doesn’t prove tap water is dangerous

22 September 2021
What was claimed

Electrolysis of tap water and distilled water shows that tap water contains something that is dumbing us down.

Our verdict

The cup of tap water going green doesn’t prove there’s anything untoward in it. The colour change is likely to be the metal electrodes of the device breaking down, which is only possible in non-distilled water.

A video on Facebook of someone appearing to ‘test’ tap water with an electrical device, alongside the caption “and we wonder why we’re feeling dumbed down” has been viewed almost 100,000 times. 

The person in the video compares a glass of tap water to one of distilled water. After the device is switched on, the tap water starts going green and then black, while nothing appears to happen with the distilled water. 

The device used appears to be an electrolysis machine and similar-looking models are readily available online

What is happening in the video?

Electrolysis is the process of using electricity to split something into its component elements: for example with water, that would be oxygen and hydrogen. The machine contains two pairs of positive and negative electrodes, allowing someone to ‘test’ two samples side by side.

For electrolysis to work, something has to be added to pure water, such as an acid or salt. Tap water conducts electricity more easily because of small amounts of calcium and other substances dissolved in it. 

Distilled water has been boiled and then condensed back into a liquid, leaving mostly pure water. The reason not much happens with the distilled water in the video is because it doesn’t conduct electricity as well because it contains so few impurities. 

Why does the tap water go green?

Oliver Jones, a professor of analytical chemistry at RMIT University in Melbourne Australia told Full Fact, via the Science Media Centre: “The colour in the video is not from the tap water but from electrolytic corrosion (electrolysis) of the metal electrodes placed in it. 

“Electrodes are usually made of iron, copper and nickel all of which decompose into coloured ion solutions when a current is passed through them in the presence of a conducting material (in this case water). A mix of these...likely contributes to the colour seen in the video.” 

So the metal electrodes releasing ions (charged particles) is likely causing the green colour, not impurities in the tap water.

Professor Mark Lorch of the University of Hull told Full Fact that the device likely used an iron electrode.

He said: “When current is passed through the system the iron from the electrode will dissolve in the water causing it to turn brownish. The distilled water is a very poor conductor of electricity so no current flows and so the electrode stays intact.”

This machine just shows tap water isn’t distilled

None of this means the tap water is unsafe. It certainly looks pretty disgusting, but this won’t happen inside you if you consume the water.

What’s more, water companies in the UK have to make sure their supply is appropriate for things like consuming and washing, and the supply is regularly tested to make sure this is the case.

Water containing some impurities isn’t necessarily bad for you and there’s no evidence it will ‘dumb you down’. For example, hard water contains calcium, but this doesn’t affect the water quality. There are stringent regulations in the UK on what levels of chemicals drinking water can contain.

The machine in the video has the potential to be very dangerous, as it could result in electric shock to the user, particularly because of its proximity to water.

This article is part of our work fact checking potentially false pictures, videos and stories on Facebook. You can read more about this—and find out how to report Facebook content—here. For the purposes of that scheme, we’ve rated this claim as missing context because the process in the video doesn’t prove that the tap water is unsafe or contains something untoward.

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