Your RO tank is not filling — work through it in this order

Does this match your symptoms?

• Tank empty or filling far more slowly than it used to
• Purifier runs continuously without ever cutting off
• No sound at all when the unit is switched on
• Pump audible but no water reaching the tank

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. Most commonTechnician job₹1,200 – ₹2,500

   1. Low or no inlet water pressure

   How to confirm it

   Open the inlet tap that feeds the purifier and time how long it takes to fill a one-litre bottle. Under about 10 seconds is comfortable; much beyond 20 seconds and your RO is likely starved. Common on upper floors, on direct municipal supply during low-pressure hours, and where an overhead tank sits barely above the kitchen.

   The fix

   If pressure is genuinely low, fit a booster pump sized for domestic RO. If pressure is fine at the tap but poor at the machine, suspect a kinked or crushed inlet pipe — check the run behind the unit, which is where it usually happens.

   Part: Booster pump, where pressure is the confirmed cause

2. Most commonYou can fix this₹150 – ₹350

   2. Choked sediment (spun) filter

   How to confirm it

   Close the inlet, release the pressure and open the first-stage housing. A healthy sediment cartridge is white or off-white. One that is brown, orange or grey through its full depth is choked and is throttling everything downstream. In hard or silty supply this can happen in as little as three months.

   The fix

   Replace the sediment cartridge. If it is choking every few months, the problem is your supply rather than the purifier — a pre-filter at the inlet point will protect it and costs less than repeated cartridge changes.

   Part: Sediment / spun filter cartridge

3. CommonTechnician job₹350 – ₹700

   3. Failed solenoid (inlet) valve

   How to confirm it

   The solenoid is the valve that lets water in when the machine calls for it. If the unit powers up, the indicator lights work, but you hear no click and no water enters, the solenoid is a strong candidate. A technician can confirm it in a minute with a multimeter across the coil.

   The fix

   Replace the solenoid valve. It is a standard part on almost every domestic RO and not an expensive one.

   Part: Solenoid / SV valve

4. CommonTechnician job₹600 – ₹2,500

   4. Failed booster pump or SMPS

   How to confirm it

   Switch on and listen. A working pump is clearly audible. Total silence with the unit powered points at either the SMPS (the power adaptor) or the pump itself. If other indicators are lit, the SMPS is at least partly alive, which shifts suspicion to the pump.

   The fix

   Replace whichever component is confirmed dead. Insist the technician tests both rather than replacing both — these are frequently swapped together when only one had failed.

   Part: SMPS adaptor or booster pump

5. OccasionalTechnician job₹150 – ₹400

   5. Stuck float valve or float switch

   How to confirm it

   The float tells the machine the tank is full. When it sticks in the 'full' position the purifier never starts, even with an empty tank. Symptom: everything looks healthy, nothing runs, tank is empty. On units with a mechanical float you can sometimes hear it free itself if the tank is gently rocked.

   The fix

   Replace the float valve or float switch. A cheap part, but it needs the tank opened, so it is usually a technician job.

   Part: Float valve / float switch

6. OccasionalTechnician job₹1,500 – ₹3,500

   6. Blocked or scaled RO membrane

   How to confirm it

   Consider this only after pressure and the sediment filter have been ruled out. A scaled membrane restricts product flow while reject water still runs to drain — so the drain line flows normally but the tank fills very slowly. On hard water without adequate pre-treatment, membranes scale fast.

   The fix

   Replace the membrane, and fix the reason it scaled. If your supply is hard, a softener or an anti-scalant stage upstream will protect the next one — otherwise you will be buying another membrane within a year.

   Part: RO membrane

When to stop and call a technician

• You have confirmed adequate inlet pressure and a clean sediment filter, and it still will not fill
• You can hear the pump but no water reaches the tank
• There is no sound and no indicator light at all — this is electrical
• The unit is under warranty, in which case none of this should cost you anything

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.