Why Myths in Water Purification Are Dangerous
A myth about your TV or mobile phone costs you money if you act on it. A myth about your water purifier can cost you your health. When myths lead people to trust water that is not safe, buy equipment that does not solve their problem, or skip maintenance that keeps their purifier working β the consequences are real and sometimes severe.
This guide addresses the 10 most widespread water purifier myths in Bangladesh with direct, evidence-based corrections.
Myth 1 β "If Water Looks Clear, It Is Safe to Drink"
The fact: The most dangerous water contaminants are invisible. Arsenic is colourless, tasteless and odourless β families in Bangladesh's arsenic-affected districts have been drinking heavily contaminated water for decades without knowing it. Bacteria, viruses, nitrates, fluoride and dissolved heavy metals are all invisible to the eye.
Clear water is good news for turbidity β nothing more. Test your water; do not assume clarity equals safety.
Myth 2 β "Boiling Water Makes It Completely Safe"
The fact: Boiling water at 100Β°C for 1 minute kills all biological pathogens β bacteria, viruses and protozoa. For microbial contamination, boiling is completely effective. However:
- Boiling does not remove dissolved chemicals β arsenic, lead, nitrates, fluoride and pesticides remain in boiled water
- Boiling actually concentrates dissolved solids β as water evaporates during boiling, TDS increases in the remaining water
- Boiling has no effect on TDS whatsoever
If your water problem is microbial only (and you have tested to confirm no chemical contamination), boiling is an effective and free solution. If your water has arsenic or high TDS, boiling makes it worse.
Myth 3 β "RO Water Is Too Pure and Dangerous to Drink"
The fact: RO water is not dangerous. The concern behind this myth is that demineralised water leaches minerals from the body β a claim that has been examined and largely rejected by the scientific community.
The WHO's comprehensive review concluded that while long-term consumption of very low mineral water without dietary mineral compensation is not ideal, drinking well-maintained RO water as part of a normal diet does not cause mineral deficiency in healthy people consuming varied food. The infinitely larger health risk is drinking contaminated water.
A mineraliser cartridge post-RO restores calcium and magnesium and raises pH β addressing any legitimate concerns about mineral content in a ৳600/year cartridge.
Myth 4 β "More Purification Stages = Better Water Quality"
The fact: The number of stages is a marketing number β not a quality indicator. What matters is whether each stage is appropriate for your specific water problem.
A 3-stage system (sediment + carbon + RO) appropriate for your water quality produces better results than a 9-stage system where 6 of the stages are redundant. Unnecessary stages add cost, require additional maintenance, and in some cases (like excessive carbon stages) can reduce water pressure.
Ask what each stage removes β not how many stages there are.
Myth 5 β "Once Installed, a Water Purifier Works Indefinitely"
The fact: This belief is responsible for more unsafe water than any other myth. A water purifier with expired filters can produce water that is worse than the source water it is supposed to treat.
- A saturated carbon filter that has not been changed can become a breeding ground for bacteria β adding contamination it was supposed to prevent
- An expired RO membrane may have a rejection rate of 60% instead of 95% β providing false reassurance while allowing significant contamination through
- A UV lamp past its rated life continues to glow but provides no germicidal protection
Replace filters on schedule. Test your water monthly with a TDS meter to catch membrane degradation early.
Myth 6 β "TDS Below 50 Is the Healthiest Drinking Water"
The fact: Very low TDS water (below 50 ppm) is chemically very pure β but it is not necessarily the healthiest drinking water. The WHO's review on nutrients in drinking water found evidence that calcium and magnesium in drinking water are associated with reduced cardiovascular mortality β and these minerals contribute to TDS.
The ideal TDS for drinking water is generally considered to be in the range of 50β150 ppm β pure enough to have removed contaminants, but retaining beneficial mineral content. Water with a mineraliser cartridge after RO typically achieves this range naturally.
Myth 7 β "UV Purifiers Kill Everything in the Water"
The fact: UV purifiers kill all biological pathogens very effectively β this part is true. However:
- UV has absolutely no effect on dissolved chemical contaminants β TDS, arsenic, heavy metals, nitrates, pesticides
- UV is ineffective in turbid water β particles shield microorganisms from UV radiation; pre-filtration is essential
- UV does not remove dead microorganism bodies from the water β they remain in the water (though they are harmless)
- A UV lamp that is past its rated life continues to glow but may not deliver sufficient UV dose
UV is excellent for microbial safety. It is not a complete purification solution for water with chemical contamination.
Myth 8 β "Branded Purifiers Always Use Better Filters Than Generic Ones"
The fact: Many purifier brands use standard industry-specification filter components (PP sediment filters, standard carbon block, standard RO membranes) and sell them at a premium under their brand label. The specification of the generic compatible replacement is often identical to the branded cartridge.
Check the micron rating of the sediment filter, the carbon type and weight of the carbon block, and the GPD rating and brand of the RO membrane. Many authorised service centres use identical components to the brand-labelled versions.
This does not mean all generics are equal β poor-quality unbranded filters exist and should be avoided. But a compatible filter from a reputable generic supplier is frequently as effective as the branded version at significantly lower cost.
Myth 9 β "High Water Pressure Improves Purification Quality"
The fact: Above the minimum operating pressure (40β60 PSI for standard RO), increasing pressure does increase membrane production rate β but it does not meaningfully improve rejection rate. In fact, extremely high pressure (above 80 PSI) can damage membranes and reduce rejection rates by forcing more water and some contaminants through the membrane under stress.
Standard household mains pressure (40β70 PSI) is ideal. A pressure reducer is recommended if your inlet pressure exceeds 80 PSI β not to improve performance, but to protect the membrane.
Myth 10 β "You Can Tell If Your Purifier Is Working by the Taste of the Water"
The fact: Taste is one of the worst indicators of water safety or purification effectiveness. You cannot taste:
- Arsenic at any concentration found in drinking water
- Lead at any concentration found in drinking water
- Nitrates
- Most bacteria and viruses
- A failing RO membrane still producing slightly better taste than source water while allowing 30β40% of contaminants through
Conversely, a properly functioning RO purifier with an exhausted post-carbon filter may produce technically safe water that tastes slightly off due to tank contact or carbon fines.
Test with a TDS meter monthly. Test with a laboratory annually for chemical and biological parameters. Taste is not a safety test.