The rule in one line
If the dissolved solids are the problem, you need RO. If the only problem is that the water might carry microbes, UV is enough. The TDS reading answers the first part outright. The second part needs a lab test, because a TDS meter cannot see bacteria, and the guide on what TDS cannot see explains why.
What UV does, and does not
A UV purifier passes water past an ultraviolet lamp. The light damages the DNA of bacteria, viruses and cysts so they cannot reproduce, and the water leaves the chamber disinfected. That is all it does. Nothing is removed; the microbes are still in the water, inert. The dissolved solids are untouched, so the TDS reading is the same on both sides of the lamp, and so is the taste.
Two things follow. First, UV needs clear water. Turbidity shadows microbes from the light, so a UV unit always has a sediment stage ahead of it, and on silty water that stage needs changing on time. Second, UV cannot help with anything dissolved: not the salty taste of high-TDS water, not fluoride, not nitrate, not hardness. If the lab report shows any of those above the limit, UV on its own is the wrong purchase however low the TDS is.
What RO does, and does not
Reverse osmosis pushes water through a membrane fine enough to hold back dissolved ions. It lowers TDS, removes fluoride and nitrate and most heavy metals, and takes out hardness along the way. It does this only to the water that goes through it, at the cost of some water rejected to drain and a membrane that wears. A domestic RO purifier of the kind sold in India is nearly always RO plus UV, and sometimes plus UF, because water sits in a storage tank after the membrane and the UV stage keeps it disinfected there. So "UV or RO" is really "UV alone, or RO with UV built in".
What RO does not do is decide how much to remove. It takes out the harmless mineral with the harmful, and on a low-TDS feed that leaves flat water. The low TDS guide is about that; the short version is that a TDS controller or mineral stage puts taste back.
When UV is enough
- The TDS reading is under about 300 ppm, and stays there through summer.
- A lab report shows fluoride, nitrate and heavy metals inside the IS 10500 limits.
- The water is clear, or a sediment cartridge can make it clear.
- The taste is already acceptable, because UV will not change it.
That describes a lot of treated municipal supply in Indian cities. On such water an RO purifier is not wrong, but it spends money removing mineral the water did not have to spare, and the TDS reference page says so in its chart.
When RO is required
- The TDS reading is above 500 ppm, or above 300 and rising through summer.
- A lab report shows fluoride above 1.5 mg/L or nitrate above 45 mg/L. Nothing but a membrane removes them at home.
- The water is a borewell supply and has not been tested; RO covers the likely risks while you wait for the report.
- The water tastes salty, bitter or chalky. UV will leave it exactly as it is.
Above 2000 ppm the choice is still RO, with a membrane rated for the feed and a softener ahead of it if the hardness is high. The high TDS guide covers that end.
Where the running cost really differs
Both types share the pre-treatment: a sediment cartridge and usually a carbon one, changed on a schedule. In the LUXGEN range those are the 10″ wound sediment cartridge at ₹190 and the 10″ coconut-shell carbon cartridge at ₹220, each rated up to twelve months. That cost is the same either way.
UV adds a lamp, replaced roughly yearly, whose price depends on the make; and a little electricity. RO adds the membrane — the 80 GPD 1812 membrane is ₹650 — replaced when its output starts climbing, a booster pump that wears, and reject water sent to drain every day the purifier runs. Over a few years RO costs more to run than UV, chiefly in membrane, pump and water, and the gap is wider on high-TDS feed, which shortens membrane life. That is the honest accounting. It is not a reason to choose UV on water that needs RO; it is a reason not to buy RO on water that does not.
Where LUXGEN fits, honestly
All three LUXGEN purifiers are RO with UV built in; the range does not include a UV-only unit. If your reading and lab report say UV is enough, the right advice is to buy one from a maker who sells one. If they say RO, the Curve is the entry point at RO + UV + UF, and the Royale Copper adds an adjustable TDS controller for feeds where you want to keep some of the mineral. Either way the cartridges and membranes on this site fit standard 10-inch housings and 1812 membrane slots, so the running cost above applies to most purifiers, not only these.
Questions
Can I use a UV purifier for borewell water?
Only if a lab report shows the fluoride, nitrate and TDS inside the IS 10500 limits, which for borewell water in most of India is not the usual result. UV disinfects; it does not remove anything dissolved. Test first, and if the report is clean and the TDS under about 300, UV is enough.
Does a UV purifier reduce TDS?
No. UV light inactivates microbes and leaves everything dissolved exactly as it was. The TDS reading and the taste are the same before and after the lamp.
Is RO better than UV?
Neither is better; they do different jobs. RO removes dissolved solids and contaminants and costs more to run. UV disinfects and changes nothing else. Water with TDS under 300 and a clean lab report needs only UV; water above 500, or with fluoride or nitrate over the limit, needs RO.