Water Purifier Buying Guide for India: RO vs UV vs UF, TDS Levels, Maintenance Costs, Water Wastage and Smart Selection

Choosing a water purifier is about matching the technology to your water. Many families buy RO because of marketing, even when their water is low in dissolved solids, and then waste water and strip useful minerals. This guide helps you decide based on facts.

Prices, specifications and product availability change often. Treat figures here as starting points and check current details before buying.

Step 1: Know your water

• Source: municipal supply, borewell, tanker, or a mix.
• TDS (total dissolved solids) measured in ppm or mg/L. A handheld TDS meter costs little. Test the tap water and ask for a free test from a seller if possible, but compare with a second reading.
• Hardness, chlorine, iron, fluoride, nitrate, arsenic and bacteria need lab tests. TDS does not show microbes, and it does not tell you whether the water is safe by itself.

The Bureau of Indian Standards drinking water standard (IS 10500) gives an acceptable TDS limit of 500 mg/L, which can be relaxed to 2000 mg/L where no alternate source exists. Very low TDS water also lacks minerals, so extremely low is not necessarily better.

Purification technologies

• RO (reverse osmosis): pushes water through a membrane that removes dissolved salts, heavy metals and many contaminants. Best for high TDS or contaminated borewell water. Drawbacks: wastes water, removes useful minerals unless it has a mineral retention feature, needs electricity and pressure.
• UV (ultraviolet): kills bacteria and viruses with UV light. Does not remove dissolved salts or chemicals, and needs clear water, so it is usually combined with a filter. Suitable for low-TDS municipal water.
• UF (ultrafiltration): membrane that removes bacteria, cysts and suspended particles without electricity in gravity models. Does not reduce dissolved salts.
• Activated carbon: improves taste and removes chlorine and some organics.
• Gravity-based candle or cartridge purifiers: cheap, no power, but limited protection.
• Combination units (RO+UV+UF+TDS controller): flexible for varying water quality.

Which one should you choose?

• TDS below about 200 and municipal supply: UV with UF or a good gravity-based filter is usually enough, and wastes no water.
• TDS roughly 200 to 500: UV+UF, or RO with a TDS controller or mineral retention to keep some minerals.
• TDS above 500, hard or brackish borewell water: RO with UV (and UF) is generally recommended, ideally with a pre-filter.
• Tanker or muddy water: add a sediment pre-filter and consider storing and settling first.
• Known fluoride, arsenic or nitrate contamination: RO is typically required. Get a lab test and follow health authority advice.

Features worth paying for

• Storage capacity: 7 to 10 litres for small families, 12 to 15 for larger ones. Higher storage helps if supply is intermittent.
• Purification rate: litres per hour. Check at your actual TDS and pressure.
• Water recovery: the share of input water that becomes pure. Older RO models recover about 20 to 30 percent; newer models claim 50 percent or more. Reuse reject water. See water conservation tips.
• Mineral retention or TDS controller: mixes some raw water or adds minerals.
• Filter change alerts and auto shut-off when the UV lamp or cartridge expires.
• Certifications: look for BIS marks and tests, and check if the product complies with relevant standards. Be wary of exaggerated claims.
• Wall-mounted, under-sink or countertop: pick according to your kitchen space.

Running costs

Look past the purchase price. Typical costs include:

• Annual maintenance contract (AMC) or service visits.
• Sediment, carbon, RO membrane and UV lamp replacements at intervals (commonly every 6 to 12 months for pre-filters, 1 to 3 years for membrane and UV lamp, depending on water quality).
• Electricity, usually modest. Estimate with the electricity bill calculator.
• Water wasted in RO.

Ask for the exact cost of every consumable and the service network in your city. Add the five-year total cost to your comparison. Track household spending using the budget calculator.

Installation and maintenance tips

1. Install near a water inlet and power point, with good space for service and a drain connection for RO reject.
2. Flush new filters as instructed before drinking.
3. Replace cartridges on time. Overused filters can release contaminants and grow bacteria.
4. Clean the storage tank periodically.
5. If you are away for weeks, flush the system before use.
6. Keep records of service dates.

Common myths

• "Everyone needs RO": not if your water is low in TDS.
• "Lower TDS means healthier": not necessarily. WHO has discussed concerns about demineralised water, and many suggest retaining some minerals.
• "Boiling is enough": boiling kills microbes but does not remove dissolved chemicals or metals.
• "Bottled water is always safer": quality varies, and it creates plastic waste.

Health basics

Safe water prevents diarrhoea, typhoid and hepatitis. If you notice persistent stomach problems after a change in water, consult a doctor. Hydration needs vary. See water intake calculator and home remedies for staying hydrated while ill.

Buying checklist

1. Test your water TDS and know your source.
2. Shortlist two or three models suited to your TDS.
3. Compare five-year costs, not just the price.
4. Check service availability and warranty terms.
5. Read recent user reviews, and verify claims.

Frequently asked questions

Do I need RO if my TDS is low?

Usually not. UV with UF or a good filter may suffice for low-TDS municipal water.

What TDS is acceptable?

The BIS limit is 500 mg/L, relaxed to 2000 where no alternative exists.

How often should I change filters?

Follow the manual; pre-filters commonly every 6 to 12 months and membranes or UV lamps every 1 to 3 years depending on water quality.

Does boiling remove TDS?

No, boiling kills microbes but does not remove dissolved salts.

How can I reduce RO water wastage?

Reuse reject water and choose models with higher recovery.

Is very low TDS water healthy?

Extremely low mineral water is not necessarily better, so look for mineral retention.

Last reviewed 8 November 2026. Rates, limits and rules change, so confirm figures with the official source before you act.