Your RO output TDS is very low — when that matters

Does this match your symptoms?

• Output TDS consistently under 30-40 ppm
• Water tastes flat, empty or metallic
• Food and tea taste different since installing the purifier
• Your input supply was already low-TDS

Work through the causes in this order

Ordered by how often each turns out to be the real cause — not by what it costs to fix. 1 of these costs nothing to resolve.

1. Most commonTechnician jobUp to ₹400

   1. TDS controller closed, or not fitted

   How to confirm it

   Check whether your model has a TDS controller or mineral blend valve. If it does and output is under 40 ppm, it is closed or nearly so. If it does not have one at all, the unit will always drive output to the floor and there is nothing to adjust.

   The fix

   Have the TDS controller opened to bring output into the 50-150 ppm range. It is a valve adjustment and should not cost a part.

2. CommonTechnician jobFree to fix

   2. RO fitted on supply that never needed it

   How to confirm it

   Measure the input TDS at the inlet tap. Below 200 ppm, RO was the wrong technology — UV plus UF would have disinfected the water without stripping it, at a fraction of the running cost and with no reject water at all.

   The fix

   If the unit is new, this is worth raising with whoever sold it. If you are keeping it, open the TDS controller as far as it goes. When it comes time to replace, do not buy RO again unless your supply has changed.

   Part: None — this is a specification error rather than a fault

3. CommonYou can fix this₹400 – ₹1,200

   3. Exhausted mineraliser cartridge

   How to confirm it

   Applies to units with a mineral or alkaline stage. These cartridges deplete, typically within 6-12 months, after which output TDS falls back to raw membrane output and the water goes flat again.

   The fix

   Replace the mineraliser cartridge on the maker's schedule. Note that this is only worth doing if you genuinely needed RO in the first place.

   Part: Mineral / alkaline cartridge

When to stop and call a technician

• Your unit has no TDS controller and you want output raised — this may need a blend valve retrofitted
• You want to establish whether you needed RO at all, which starts with a proper input measurement

When replacement beats repair

Costs shown are indicative bands for India, published so you can sanity-check a quote — they are not quotations, and they vary by brand, city and whether the technician is brand-authorised. Last reviewed 2026-08-08.