Two very different technologies compete in Indian homes: the modern RO water purifier and the traditional gravity water filter (candle filter). One requires electricity, uses a pump and membrane, and costs Rs 8,000–20,000. The other needs no electricity, uses ceramic candles, and costs Rs 500–3,000. But which one actually makes your water safe? The answer depends entirely on your water source and contamination level.
How Each Technology Works
How a Gravity Water Filter Works
A gravity filter (also called a candle filter or ceramic filter) works purely on gravity — water poured into the upper chamber passes through ceramic candle filters under gravity into the lower chamber. The ceramic material has pores small enough (0.5–1 micron) to trap bacteria, sediment, and some protozoa. No electricity is required. Activated carbon in some models removes chlorine and improves taste.
How an RO Purifier Works
An RO (Reverse Osmosis) purifier uses an electric pump to force water at high pressure through a semi-permeable membrane with pores of 0.0001 microns — thousands of times smaller than a ceramic filter. This removes bacteria, viruses, heavy metals, dissolved salts, chemicals, and fluoride that a gravity filter cannot touch.
Detailed Feature Comparison
| Feature | Gravity Filter | RO Purifier (Alkin) |
|---|---|---|
| Electricity needed | No | Yes (25–50W) |
| Bacteria removal | Yes (95–99%) | Yes (99.99%) |
| Virus removal | No | Yes (UV stage) |
| Heavy metal removal | No | Yes (RO membrane) |
| TDS reduction | Negligible | 90–95% |
| Fluoride removal | No | Yes |
| Arsenic removal | No | Yes (85–95%) |
| Chemical/pesticide removal | No | Yes |
| Purchase cost | Rs 500–3,000 | Rs 8,000–20,000 |
| Annual maintenance | Rs 200–600 (candle replacement) | Rs 2,000–3,500 |
| Works during power cuts | Yes | Stored water available |
| Alkaline water output | No | Yes (Alkin models) |
When Is a Gravity Filter Enough?
A gravity filter provides adequate protection ONLY when all of the following conditions are met:
- Water source is clean municipal supply (not borewell/tanker)
- TDS is below 200 mg/L
- No heavy metal contamination (arsenic, lead, fluoride) in your area
- No chemical contamination (agricultural or industrial areas)
- You live in a location with no history of water-borne disease outbreaks
In India, these conditions are rarely met consistently — particularly the heavy metal and chemical contamination criteria. For most Indian households (especially those on borewell water or in contamination-prone areas), a gravity filter is insufficient protection.
The Verdict: Which Should You Choose?
Choose a gravity filter if: You have confirmed low-TDS, clean municipal supply; you need a backup during power cuts; budget is extremely limited (below Rs 1,000).
Choose an Alkin RO purifier if: You use borewell water; your city has known TDS above 300 mg/L; your area has fluoride, arsenic, or heavy metal contamination; you have children, elderly, or immunocompromised family members; or you want the peace of mind of comprehensive protection.
FAQs — RO Purifier vs Gravity Filter India
For most Indian families, the choice is clear — the health protection difference between a gravity filter and an RO purifier is not marginal, it is fundamental. Choose an Alkin RO purifier that matches your water source and budget, with free installation and genuine after-sales service.
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