Water purifier myths: boiling is enough, RO strips the good minerals

Most of what people believe about water purifiers is half right, which is why the myths survive. Boiling does kill germs; it just does not do anything about salt. RO does strip minerals; it just takes out far more of what you do not want than what you do. A TDS meter is useful; it just does not measure the thing people think it measures. Here are the ones we hear most in Nellore kitchens, with the part that is true and the part that is not.

"We boil our water, so we don't need a purifier"

True: a rolling boil inactivates bacteria, viruses and cysts. On clean, low-TDS municipal supply, boiled water is microbially safe.

Not true: boiling removes nothing dissolved. Hardness, salt, fluoride, nitrate and iron all stay, and as steam leaves the pot they are slightly more concentrated in what remains. On a borewell reading 900 TDS, boiled water is 900-TDS water that is safe from germs and still hard, still salty, still scaling your kettle. If your water is borewell, a purifier is doing a job boiling cannot.

"RO removes all the good minerals, so RO water is dead"

True: a membrane does not know calcium from sodium. It holds back most dissolved salts, good and bad together. The output tastes flat to many people, and water at very low TDS is unpleasant to drink.

Not true: that this makes RO water harmful, or that drinking water was ever your main source of minerals. Food is. The practical answer is a TDS controller or a mineraliser stage that brings the output up to a pleasant range — set by a technician for your inlet water — and a UV stage after any blending so that raw water mixed back in is still treated. What matters is that the water leaves the unit in a sensible range and microbially safe, not that it is as close to zero as possible.

"Low TDS means pure water"

True: TDS is a quick, cheap way to see how much dissolved salt is in water, and to watch a membrane age over months.

Not true: TDS is a purity score. A TDS meter reads dissolved salts, nothing else. Bacteria, viruses, and many contaminants do not register on it at all. Low-TDS water from a contaminated source can be unsafe; 250-TDS water from a clean treated supply can be excellent. Use the meter for what it is — a salt gauge and a membrane-health trend — and let the UV or UF stage do the microbial job.

"The filters last a year; the sticker says so"

True: on clean, low-sediment water, the sticker is often about right.

Not true: that it applies to your house. Filter life is set by what goes through, and in Nellore a silty borewell in November or a tanker summer can fill a sediment candle in a fraction of that. The sticker is a maximum. Look at the candle, time the fill, measure the output.

"More stages means a better purifier"

True: RO alone leaves microbes that can grow in the storage tank; a UV stage after it matters. A sediment and carbon stage before the membrane protects it. So several stages are genuinely useful.

Not true: that stage count is a quality measure. Two mineraliser stages, an "alkaline" stage and a decorative copper cartridge are not protecting you from anything. What matters is whether the unit suits your water: RO plus UV for high-TDS borewell or tanker supply; UV plus UF for low-TDS treated supply. The rest is marketing.

"If the light is on, the UV is working"

True: the indicator tells you the lamp circuit has power.

Not true: that the lamp is doing its job. UV lamps lose germicidal output well before they stop glowing, which is why they are replaced on time — roughly yearly — rather than on failure. A lamp that looks fine at two years is mostly a night-light.

"RO water is safe to store for days"

True: it will not go off the way milk does.

Not true: that it stays as clean as it came out. Purified water has no chlorine left to hold growth back. In an open vessel in a warm kitchen, or in the unit's own tank after a week's holiday, a film starts. Drain a tank that has sat for days, keep stored water covered, and clean the dispensing tap spout — the most-handled part of the whole system.

"The purifier is fine because the water tastes fine"

True: taste catches exhausted carbon and a stale tank.

Not true: taste catches a tiring membrane or a dead UV lamp. Neither announces itself on the tongue until late. A monthly TDS reading and a yearly lamp change are the checks taste cannot make for you.

What to actually do

Know your inlet TDS. Choose the technology for that water, not for the number of stages on the box. Change filters on condition, not on the sticker. Keep the tank and tap clean. Have the UV lamp replaced on time. And when the water tastes wrong or the flow drops, a service visit — ₹299 on our rate card for the filter check and service, or the same for a taste and smell flush — will tell you what is actually going on, rather than what the myth says.