Can Electrolysis Prove the Presence of Pesticides in Bottled Water?

A viral video shared on X (formerly Twitter) has attracted millions of views. In the clip, a man attempts to prove that bottled mineral water is heavily contaminated by using an electrolysis device with an anode and cathode. As the current passes through the water, the liquid turns dark — blackish and greenish — leading him to claim that pesticides and harmful substances are being “burned out” of the water.

The visual result is striking. But does it really prove contamination — or is it a misleading demonstration?

Why the viral electrolysis test is misleading

In the video, glasses of bottled mineral water are connected to a small electrolysis device. After a few minutes, dark particles appear in the water. The presenter suggests this reveals hidden pesticides and pollutants.

However, chemists and science communicators have repeatedly explained that this interpretation is incorrect. Electrolysis does not “burn” pesticides out of water. In reality, the reaction primarily involves the electrodes themselves.

When an electrical current passes through mineralised water, dissolved salts allow the current to flow. If the electrodes are made of iron (as in many low-cost devices), the metal can corrode during the process. This releases iron ions into the water, which oxidise and form coloured compounds — typically greenish or brownish particles.

In short, the dark residue seen in these demonstrations is usually oxidised iron from the electrode, not pesticides.

How electrolysis of water actually works

Electrolysis separates water into hydrogen and oxygen using electricity. However, when minerals such as calcium, magnesium, sodium or potassium are present, they increase conductivity. The more mineralised the water, the more visible the reaction can appear.

If one of the electrodes contains iron, the current can cause it to dissolve into the water. This produces ferrous ions, which oxidise and form coloured deposits. The darker the colour, the more mineral content — not necessarily the more pollution.

This means the test primarily demonstrates mineral content and electrode corrosion, not pesticide contamination.

Are pesticides present in drinking water?

Pesticides can enter surface and groundwater through agricultural runoff. In the UK, water quality is strictly regulated by the Drinking Water Inspectorate (DWI), and limits are aligned with UK and European standards.

The regulatory limit for any individual pesticide in drinking water is 0.1 micrograms per litre (μg/L). Importantly, this is a precautionary standard, not a toxicological threshold. It reflects a commitment to maintaining very high water quality rather than indicating danger at that level.

The UK Health Security Agency (UKHSA) assesses health risks where exceedances occur. In most cases, drinking water contributes only a small proportion of total pesticide exposure compared to food and environmental sources.

That said, long-term environmental contamination remains an ongoing concern, particularly for groundwater resources. Reducing pesticide runoff and protecting water catchments remain public health priorities.

Is bottled mineral water always pure?

Bottled water is subject to regulation, but it is not automatically free from contaminants. Independent investigations and environmental studies have raised questions in recent years.

For example, a 2024 analysis by environmental group Pesticide Action Network Europe reported the presence of trifluoroacetic acid (TFA), a persistent breakdown product of certain pesticides, in a significant proportion of bottled water samples tested. While concentrations were generally low, the findings prompted debate about long-term environmental contamination.

Separately, research published in early 2024 by scientists at Columbia University suggested that bottled water may contain far higher levels of microplastics than previously detected, including nanoplastics. The health implications of these findings are still under scientific investigation.

These studies do not prove bottled water is unsafe, but they highlight that “natural” does not necessarily mean entirely free from environmental influence.

Does filtration make sense at home?

For most UK households, tap water meets strict safety standards. However, some people choose additional filtration for reasons including taste, precaution, or concerns about ageing pipework.

Gravity water filtration systems offer a simple way to reduce certain contaminants such as chlorine, sediment, some heavy metals and selected organic compounds, depending on the filter media used.

These systems operate without electricity, allowing water to pass through mechanical and activated carbon filters. While they do not “burn” pollutants like the electrolysis myth suggests, they can reduce the concentration of some substances and improve taste.

If you're interested in understanding more about persistent pollutants such as PFAS, you can read our guide on where PFAS are found.

The bottom line

The viral electrolysis video does not prove bottled water contains pesticides. The dark residue seen in such demonstrations is typically caused by corrosion of the electrode and reactions involving minerals already present in the water.

Both tap water and bottled water are regulated, but environmental contamination is a complex issue. Rather than relying on dramatic online demonstrations, it’s best to look at independent laboratory testing and official water quality reports.

Understanding how water treatment works — and how misinformation spreads — is the best defence against unnecessary alarm.