This post contains affiliate links. If you buy through them, Ease Advise may earn a small commission at no extra cost to you.
Which water purifier should you buy: RO, UV or UF? The short answer is that your water decides it. Measure the TDS of your tap or borewell water first. If it is low and the supply is municipal, a UV or UF unit may be enough. If the TDS is high, or the source is borewell or tanker water, RO is the technology that actually reduces dissolved salts. This guide explains the difference in plain terms, based on published sources (information as of 2 November 2026).
What RO, UV and UF actually do
These three names describe three different jobs. Many buyers assume they are just “better” and “best” versions of the same thing, which is why they overspend or buy the wrong type.
- RO (reverse osmosis): a membrane that removes dissolved salts, and with them many heavy metals and chemicals. It needs electricity and sends some water to drain as reject water.
- UV (ultraviolet): a light chamber that targets bacteria, viruses and other microbes. It does not remove dissolved salts, and it works best on water that is already clear.
- UF (ultrafiltration): a porous membrane that holds back suspended particles, cysts and bacteria. It can work without electricity but does not remove dissolved salts or chemicals.
Most popular models combine these, for example RO+UV or RO+UV+UF, so that one box handles both dissolved and biological problems. India Water Portal notes that RO is the only common domestic filter that reduces dissolved solids; UV and UF do not.
Understand TDS before you shop
TDS (total dissolved solids) is the total amount of dissolved minerals and salts in water, shown in mg/L or ppm. Under the Bureau of Indian Standards drinking water specification IS 10500:2012, the desirable limit is 500 mg/L, and 2,000 mg/L is the permissible limit only where no better source exists. Hardness has its own limits: 200 mg/L desirable and 600 mg/L permissible. According to India Water Portal, WHO has proposed no health-based guideline value for TDS and treats water below about 600 mg/L as generally palatable.
Two cautions. First, TDS is only a total. It cannot tell you whether arsenic, fluoride or nitrate is present, and these are harmful even at low levels. Second, lower is not automatically better: India Water Portal points out that drinking water should contain some minerals. A basic hand-held TDS meter is a cheap first step; check the current price before buying.
Which type suits which water
Buying guides do not agree on exact TDS cut-offs. One Indian guide says RO is essential at 500 and above, while UV or UF can work below that; others draw the line at different numbers. Treat the table below as a starting point, not a rule, and confirm with your own test.
| Feature | RO | UV | UF |
|---|---|---|---|
| Removes dissolved salts | Yes | No | No |
| Targets microbes | Mostly, with UV added | Yes | Bacteria and cysts |
| Needs electricity | Yes | Yes | Often not |
| Water wastage | Reject water (one guide says 30-50%) | None | None |
| Best for | Borewell, tanker, high TDS | Clear, low-TDS municipal water | Low-TDS water with suspended dirt |
| Upkeep | Moderate to high | Low | Low |
The water wastage question
RO wastage figures vary by source. One guide quotes 30-50% wastage; India Water Portal gives an example where 3 litres of input yields about 1 litre of clean water and 2 litres of reject. Both agree the reject water is not clean, though it can be reused for mopping or cleaning. If your water is already low in TDS, you can avoid this loss by choosing UV or UF.
Mineral balance and TDS controllers
Some RO models blend a little treated non-RO water back in, or add mineral cartridges, to improve taste. This is a trade-off. A taste adjustment does not guarantee safety, and Urban Company’s guide warns that blending systems may reintroduce contaminants if the source water is questionable. If your source is uncertain, a full RO path is the cautious option.
Certification, filters and service
Ask the brand which standard or certification the purifier has been tested against, and look for that detail on the box, manual or product page rather than relying on words like “100% pure”. Keep the invoice and warranty card, as you will need them for service claims.
Service matters as much as the purifier. According to Urban Company’s guide, most systems need servicing every 6 to 12 months plus periodic filter replacement. Brands often claim filters last up to two years, but the same guide says independent tests and user experience suggest some need replacing within 6 to 12 months. Before buying, check whether the brand has a service centre in your city and what a full service kit costs.
How to choose: a practical checklist
- Test your water. Note the TDS reading from your actual tap or tank, and ask your municipality or a lab about fluoride, arsenic or nitrate if you live in an area known for them.
- Match technology to the source. Low-TDS municipal water points to UV or UF; borewell, tanker or high-TDS water points to RO (with UV added for microbes).
- Check household size and storage. Work out how much drinking and cooking water your family uses in a day, and pick a storage tank and purification rate that comfortably cover it, especially if your area has power cuts.
- Confirm certification and warranty. Ask what standard the unit is tested against, what the warranty covers, and keep the invoice.
- Price the running cost. Ask for the service kit price and local technician availability. Guides give a wide budget range of roughly Rs 5,000 to over Rs 30,000 for purifiers.
- Plan for power and space. RO needs a power socket and a drain or reject-water plan. If you want to compare models, you can browse RO+UV water purifiers or UV+UF models for low-TDS water, then check the current price and specifications.
Buying for a kitchen revamp? Our guide to an eco-friendly kitchen may help you plan counter space. Travelling with a bottle or filter instead? See the travel water purifiers and filters article, and for indoor air at home, read our air purifier buying guide.
Frequently asked questions
Is RO water bad because it removes minerals?
Not necessarily, but over-treating low-TDS water is wasteful. India Water Portal says removing too much TDS changes taste and pH, and that drinking water should contain some minerals. If your water is already low in TDS, a UV or UF unit is a more sensible fit. If you need RO, a model with a mineral or TDS-adjusting feature can improve taste, though not safety.
Does a UV purifier remove chemicals or salts?
No. UV is meant for microbes such as bacteria and viruses. It does not remove dissolved salts, heavy metals or chemicals, and it performs best when the water is already clear. If chemical contamination is a concern in your area, talk to a testing lab rather than relying on a UV label.
How often should I service a water purifier?
Published guidance suggests every 6 to 12 months for most systems, with filters replaced as needed. Hard water or very dirty source water can shorten filter life, so follow the brand’s schedule and the signs in your own unit, such as falling flow or a change in taste.
Bottom line
Do not start with brand names. Start with a TDS reading and your water source. Choose RO (usually with UV) for borewell, tanker or high-TDS water, and a UV or UF unit for clear, low-TDS municipal supply. Then compare certification, filter costs and local service, because those decide how the purifier behaves over the next few years. Where fluoride, arsenic or other specific contaminants are suspected, get the water tested rather than relying on TDS alone.
Sources
- India Water Portal: FAQ on total dissolved solids
- CheapestInIndia: Buying guide for RO, UV and UF purifiers
- Urban Company: How to choose the right RO for your home
- IIT Kanpur: Drinking water quality (IS 10500:2012 values)
