Most purifiers use several stages. Each stage wears out at a different speed, so there is no single "change all filters" date. Here is a practical schedule for a typical family using 10–20 litres of purified water a day.
The stages inside a typical RO
- Sediment filter — traps sand, rust and mud.
- Pre-carbon filter — removes chlorine and odour that would damage the membrane.
- RO membrane — removes dissolved salts, heavy metals and most microbes.
- Post-carbon filter — polishes taste.
- UV / UF — extra disinfection.
- Mineral / copper / alkaline cartridge — adds back minerals for taste (optional).
Recommended replacement intervals
| Part | Normal water | Hard / high-TDS / iron water |
|---|---|---|
| Sediment filter | 6 months | 2–3 months |
| Pre-carbon filter | 9–12 months | 6 months |
| RO membrane | 2 years | 12–18 months |
| Post-carbon filter | 12 months | 9–12 months |
| UV lamp | 12 months | 12 months |
| Mineral cartridge | 12 months | 9–12 months |
These are guidelines. A technician should decide based on how the parts actually look and on a TDS rejection test — not just the calendar.
Why the cheap filters matter most
Skipping a sediment filter change to save a few hundred rupees is the most expensive mistake. Mud and chlorine reach the membrane, foul it, and you end up replacing a part that costs several times more.
Get it done right
We stock filters and membranes for all major brands and assembled purifiers. See filter replacement, membrane replacement, or save more with an RO AMC plan.