Black Magic: This glass contains high-quality bottled mineral water from a reputed French brand. We gave it to a water filter company agent in the guise of tap water. Using a dubious electrolysis test, he turned it into a horrid brownish black colour and declared the water unfit even for washing utensils or cooking. Test case: Another agent was given this bottled mineral water from a famous local brand. We presented it for the ‘water quality test’ saying it was our drinking water from an ordinary brand. The agent ran a test on it and attributed the dark colour to contamination, which he claimed could cause a host of diseases. Glass apart: This is a sample of the filtered water a third sales agent brought along. He said it didn’t turn dark because its quality was superior to our ‘contaminated and impure’ samples Image Credit: © XPRESS/Mazhar Farooqui

Dubai: An XPRESS sting operation has uncovered a scam where dodgy firms go door to door using scare tactics and fraudulent methods to sell overpriced water filters and purification systems.

Typically, the scam runs like this: A sales agent calls you and offers to test your water quality. Because it's free, you don't mind a little demo. In this scenario, the sales agent comes to your house and asks for samples of your tap and bottled drinking water.

He fishes out a device with multiple rods, plugs it into a power socket and immerses the rods into the samples.

Seconds later, the colour of both water samples turns a horrid brownish black. As the water colour changes before your disbelieving eyes, the agent warns you that your water is highly contaminated and could cause a host of diseases, including kidney failure and cancer.

The best solution, you are told, is to buy their ‘breakthrough' water treatment device. To illustrate his point, the agent proceeds to do the same test with a sample of water filtered by their company's product. And guess what, the water colour remains largely unchanged.

Their water filter could cost anywhere between Dh2,000 and Dh4,000. But what the heck, it's still a small price to pay for the health and safety of your family.

At this point, you have been conned by one of the oldest tricks in the chemistry book.

How we set them up

To expose the lies in the high-pressure sales, we posed as potential customers and contacted sales agents of various firms for a live demonstration at a house.

The unsuspecting agents took the bait and set out to con us. Unknown to them, we had our bottled drinking and tap water samples ready in separate glasses. Not some ordinary water, but from two of the biggest and most reputed bottled mineral water companies in the world.

"Tut-tut... so this is what you use for cooking and bathing and this is what you drink. Too bad. You may not see it with the naked eye but both contain toxins," said an agent grimly, as he held aloft the glasses which he thought contained our tap and drinking water. Out came the electrical device and the rods were dipped into the samples.

Almost immediately, the samples turned a yucky cola brown colour. "See for yourself. These chemicals and impurities can cause ulcers, kidney stones, gall bladder disease and cancer. Your water is unfit for human consumption. It's dangerous to even use it for bathing or cooking," he declared before proceeding on a long lecture strewn with pseudo-scientific rubbish.

Offers for tea or water during the demo were sternly declined. "Sir, how can I have anything in a house where water is contaminated with such dangerous chemicals? It's the same problem everywhere in the UAE, which is why I carry my own filtered water," he said, taking out a water bottle from a bag. He poured it into a glass and ran his test on it. "See, it remains clear. No impurities."

But what about when he runs out of it and has no immediate access to his filtered stuff?

The agent named a French brand he drinks in such situations. Turns out it's the same brand we gave him for the test - and it turned brown (see picture 1).

The same evening we called another agent. She was given two popular local brands in the guise of tap and bottled drinking water. The results were the same (picture 2) "You're compromising your family's safety," she said, elaborating on the virtues of her company's seven-stage reverse osmosis ultraviolet water filter system.

So, why are reputed brands of water ‘failing' the test and what's causing them to turn so dirty?

Scientific explanation

The explanation lies in science - or to be precise - in the sales agent's ‘magical' device. It's basically a portable electrolysis kit, also known as the precipitator. Some run on batteries while others run on electricity but they work the same way.

The sales agents use it to conduct a chemistry experiment called electrolysis. Ask any science student and he will tell you that when electric current is passed through water using electrodes, it breaks down into oxygen and hydrogen and starts decomposing. Since the electrode is made of iron, which is reactive, it oxidises to create rust (ferric hydroxide). It (ferric hydroxide) does not dissolve readily and results in the dark sludge you see in the test. This means the rust comes from the electrodes - not from your building water tank or pipe as you're made to believe. The terrifying murky colour is a result of electrodes reacting with the minerals in the water. These are safe minerals like calcium and magnesium and are good for your health.

Only minerals react to the current. Bacteria, virus etc do not. So no test results for them.

The water samples carried by the sales agents didn't change much during the electrolysis because it did NOT have any dissolved solids or minerals. No minerals means no electricity. No electricity means no electrolysis. No electrolysis means no reaction and, therefore, no sludge. It's that simple (picture 3).

We took their ‘contamination-free' water with a pinch of salt. Literally. We added some salt to it and asked them to redo the test. Two of them refused and the third stopped just as his water started turning a gooey black.

Several residents told XPRESS how they were conned into buying the purification systems after seeing the tests. In all cases, fear was the motivating factor.

Dubai Municipality's Senior Food Studies and Surveys Officer Bobby Krishna said the water provided by municipality and bottled companies is absolutely safe.

"We have stringent measures. The water provided by Dubai Municipality is safe for drinking so long as your water tank is clean. If people have doubts about their water quality, they should get it checked at municipality-approved laboratories, not by dubious electrolysis or TDS (Total Dissolved Solids) tests," said Krishna.

James Day, Managing Director of Smashing Services, a Dubai cleaning company that disinfects water tanks and pipes, said water quality can be checked only in a proper laboratory. "You need sophisticated equipment for it. You can't do it with a device that you carry along in your pocket. If you want to install filters, go for reputed brands. But ensure the filters are regularly replaced. A poorly maintained filter can cause bacterial growth," he warned.

So what's the bottom line? The products these companies are selling are just like any other water purification system that works on the principle of reverse osmosis or 5/7 stage filtration. The problem is that they use cheap gimmicks to find faults in the water provided by bottled companies and municipality and capitalise on the unfounded fears of panicky residents to sell their products.

But water purification companies denied any wrongdoing. When confronted with the evidence their common refrain was: "We are only trying to create awareness among residents."

How our sting operation unfolded

The plan

The favourite ploy of water filter firms is to contact residents and offer a free ‘check-up' of their tap and bottled drinking water. During the demo, the water turns murky and panicky residents buy the filters. To uncover the scam we pose as customers and call sales agents of various firms to a house for a test of our water quality.

The set-up

When they take the bait and come, we give them samples from reputed international and local brands in the guise of tap and bottled water.

We DON'T give them tap water at all. Agents look at the samples and say they contain harmful chemicals which are invisible to the naked eye and offer to run some tests to prove their claims.

The tds trick

Sales agents conduct a Total Dissolved Solvency (TDS) test with a hand-held meter to determine the amount of dissolved solids in our drinking water and compare it with the result of their own filtered sample. They declare that our water has far too many minerals and is therefore unfit for consumption.

The electrolysis scare

To beef up their bogus case, they use an electrolyser to pass current through our samples. Unknown to them both samples are high quality bottled mineral water. Yet within seconds they turn into a dark brown sludge. Agents point at the glass they thought contained tap water and attribute the brown colour to rust particles in our building tank and pipe. They say it's unfit for cooking and bathing. They find fault with our bottled water too and warn us against a host of diseases including cancer. The solution we are told is their company's water filter.

Pinch of salt

The agents then run the electrolysis test on their filtered water. Since it has no or very little mineral, its colour remains largely unchanged. They say it's because their water is free of contamination. We add some salt to it and ask them to do the test again. Two agents refuse while a third stops midway as his sample starts turning a gooey black because of the added salt mineral.

Cheap chemistry trick

When current is applied to water containing salt the water will begin to decompose and turn murky. If the electrode serving as the anode is made of iron, some of the iron will go into the water, resulting in the formation of ferric hydroxide, giving it a dirty brown appearance within seconds

XPRESS alert

Reputed water filter brands will never use cheap gimmicks to sell their products. If a sales agent is trying to con you it tells you a few things about the kind of people running the company. So, if you are looking for after-sales service or warranty, you know what to expect.

Things you need to know


  • Developed countries have disclaimed the electrolysis test because it gives the wrong impression that your water is dirty.
  • Your water changes colour during the tests because it contains minerals and minerals react with electrodes when a current is passed through them.
  • Filtered water doesn't change colour simply because it has very little or no minerals. No minerals mean no electricity and no electricity means no reaction and thus no sludge.
  • Your bottled water is absolutely safe to drink. The water supplied by the municipality is also safe to drink if your building water tank is clean.
  • If you still want to install a water purification system go for a reputed brand. Don't be fascinated by water filters that come with electromagnets, electrolytic processes, molecular oscillations etc. There is no credible evidence that any of these water-conditioning methods really work.

Here is what happens during electrolysis:

Positively charged ions move to the negative electrode during electrolysis. They receive electrons and are reduced.

Negatively charged ions move to the positive electrode during electrolysis. They lose electrons and are oxidised.

Source: www.bbc.co.uk (GCSE Bitesize)