The Honest Answer: Most People Replace Too Late


Studies of RO systems in Indian homes consistently find that most membranes are operating past their effective service life. An expired membrane can drop from 98% rejection to below 70% — and the water still looks perfectly clear. This is the core problem: unlike a clogged pre-filter (which reduces flow), a degraded membrane silently fails to remove dissolved contaminants.


How Long Does an RO Membrane Last?


  • **Typical lifespan:** 12–24 months under normal residential use
  • **High TDS water (above 1500 ppm):** closer to 12 months
  • **Well-maintained pre-filters, low TDS:** potentially up to 2–3 years
  • **Key variable:** pre-filter maintenance is the single biggest factor

Clear Signs Your Membrane Needs Replacing


1. TDS rejection is dropping

This is the most reliable indicator. Measure your source water TDS and your purified output TDS with a TDS meter. Calculate rejection: ((source − output) / source) × 100. If rejection falls below 90%, plan a replacement. Below 80% is urgent.


2. Purified water flow is noticeably slower

If your storage tank fills much more slowly than before, and you've already replaced sediment and carbon pre-filters, the membrane itself may be fouled or degraded.


3. The membrane is over 12 months old

If you don't know when the membrane was last replaced — replace it now. When in doubt, the cost of a new membrane is small compared to the cost of prolonged exposure to inadequately treated water.


4. Unusual taste or odour in purified water

While taste changes are often caused by a due-for-replacement post-carbon filter, a significantly degraded membrane can also contribute.


What Happens If You Don't Replace It?


  • **Rejection efficiency drops:** water may contain elevated TDS, heavy metals, and other dissolved contaminants despite passing through the "RO"
  • **Membrane fouling becomes irreversible:** early fouling is often flushed; advanced fouling permanently reduces performance
  • **Increased stress on the system:** a partially blocked membrane requires higher pressure, stressing the pump

Replacement Checklist


  • ✅ Replace sediment filter every **3–6 months**
  • ✅ Replace carbon pre-filter every **3–6 months**
  • ✅ Replace RO membrane every **12–24 months**
  • ✅ Replace post-carbon filter every **12 months**
  • ✅ Test output TDS every **3–6 months** with a TDS meter
  • ✅ Register your product to receive CLARYN maintenance reminders