TDS (Total Dissolved Solids) is the total amount of salts, minerals and metals dissolved in water, measured in parts per million (ppm). A reverse osmosis membrane removes up to 90–99% of them — which is great for high-TDS borewell water, but can leave water with very few useful minerals.
Why RO water alone can be 'too pure'
If your input water is 900 ppm, RO output may drop to 20–40 ppm. That water is safe, but it tastes flat and lacks calcium and magnesium. BIS recommends drinking water below 500 ppm, and most people prefer the taste between 80 and 150 ppm.
The TDS controller workflow
1. **Split the flow:** After the sediment and carbon pre-filters, a small portion of water is diverted away from the RO membrane. 2. **Adjust the valve:** The TDS controller is a precision valve. The technician turns it to decide how much of this water is blended back. 3. **Blend:** The diverted water mixes with the low-TDS RO water, raising TDS to your chosen level. 4. **Disinfect:** The blended water passes through UV and/or UF so the bypassed portion is also free of bacteria and viruses. 5. **Final polish:** A post-carbon or mineral cartridge improves taste before water reaches your tank.
Setting the right level
- **Input TDS under 300 ppm:** Keep more blending for natural minerals.
- **Input 300–800 ppm:** Blend to about 100–150 ppm.
- **Input above 1,000 ppm:** Keep blending minimal — the bypassed water would carry too many salts.
Why it must always be followed by UV
The bypassed water never passes through the membrane, so it needs a separate disinfection step. That's why every iDrink RO with a TDS controller also has a UV chamber after the blending point.
Bottom line
A TDS controller gives you the safety of RO with the taste and minerals of natural water. iDrink technicians test your tap TDS at installation and set the controller for your home — free, and re-checked at every service visit.