The short answer
If your RO gives no water at all, suspect the power adaptor/SMPS or input pressure first — in Delhi the little plug-in adaptor is the part that voltage swings and power cuts kill most often, not the membrane. A slow trickle is almost always choked pre-filters from tanker or borewell sediment; a won't-stop overflow is usually a stuck float or solenoid valve. Before calling anyone, run three free checks: confirm live power at the socket, confirm the input tap is open and flowing, and note how old the pre-filters are.
An RO purifier looks complicated — a box of cartridges, a pump, a tank and a nest of tubes — but it fails in a small number of predictable ways. Water comes in, a pump pushes it through a set of filters and a membrane, clean water collects in a storage tank, and a float switch tells the system to stop when the tank is full. When something goes wrong, the symptom you can see usually points straight at the part that has failed.
In Delhi NCR two things skew the odds. The first is voltage: an RO pump needs steady mains power, and the low-voltage patches and frequent cuts this city is used to are hard on the small adaptor that runs it. The second is sediment: tanker-fed and borewell water carries fine silt and dissolved hardness that clogs the pre-filters far faster than the polished municipal supply these machines were designed around. A large share of "my RO stopped working" calls in Delhi are really one of those two stories.
Work through the symptoms below in order. The free checks come first, because surprisingly often they are the answer.
A note on how we work. XpertWorker is a marketplace, not a service company. We do not set any professional's price and we never charge you a paisa. When you need a technician we connect you with independent professionals whose identity we verify with PAN and Aadhaar. They inspect the unit, quote you directly and free of charge before doing anything, and you pay them directly once the work is done. If it is ballpark costs you are after, our RO service cost and TDS guide covers the indicative market ranges — this page is about finding out what is wrong in the first place.
In this guide
Before you call anyone, check these three things
All three are free, take about five minutes, and between them they explain a large share of the "RO not working" calls in Delhi. Do them before you let anybody open the unit.
- 1. Confirm the power actually reaching the unit. An RO runs off a small plug-in adaptor (an SMPS). Check the machine is switched on at the socket, that the ON indicator is glowing, and — this is the Delhi one — that the socket itself has power right now and is not on an inverter line that has dropped the RO to save load. Try the same socket with a phone charger. No light on the RO and no obvious reason usually means the adaptor or the socket, not the membrane.
- 2. Check the input water is on. Follow the inlet tube back to the tap or line that feeds the RO and make sure that tap is fully open and the supply is flowing. An RO cannot make water it is not being given. If your building runs on a pump-and-tank schedule, the RO may simply be waiting for the next fill.
- 3. Work out how old the filters are. When were the pre-filters (the sediment and carbon cartridges) last changed? If the honest answer is "I don't remember" or "over a year", keep that in mind — in Delhi's water a choked pre-filter is one of the commonest reasons an RO slows down or stops, and it is a routine service rather than a major repair.
If power is present, the input tap is open, and the filters are reasonably fresh, and it still will not work — then it is time to match your symptom to a section below and call someone with information instead of panic.
Want a real quote for your own job?
Get free quotesNo water at all coming out
Nothing from the tap, and the storage tank feels empty when you lift or tap it. Once you have confirmed the three free checks above, these are the likely causes, roughly in order.
- Dead adaptor / SMPS (very common in Delhi). The little power adaptor is the weakest link, and this city's voltage swings and outages wear it out. If the unit is completely dead — no indicator, no pump hum — the adaptor is the first suspect. It is an inexpensive, quick swap for a technician and a far more likely answer than anything inside the machine.
- No input pressure. Many RO systems need a minimum incoming water pressure to operate, and some have a low-pressure switch that stops the pump to protect it. If your supply is gravity-fed from an overhead tank on a low floor, or the building pressure is weak at that hour, the RO may simply refuse to run. A booster pump is the usual fix, but get it confirmed before buying one.
- Empty tank plus a stopped pump. If the pump is not humming when the tank is empty, the fault is upstream of the membrane — power, adaptor, the pump itself, or the low-pressure cut-off. A dead pump is less common than a dead adaptor, so do not let anyone jump to it first.
- Fully choked pre-filter. A sediment cartridge that has silted up completely can starve the system to the point where no clean water is produced. This is the Delhi sediment story in its worst form, and it points to a filter change, not a new machine.
A dead unit almost always comes down to power or the adaptor. The membrane — the expensive part — is rarely the reason there is no water at all; a failing membrane usually shows up as slow flow or bad taste, not total silence.
Water comes, but slowly — a thin trickle
The RO works, but the tank takes hours to fill, or the tap gives a weak stream where it used to run freely. This is the single most common Delhi complaint, and the cause is nearly always the same.
- Choked pre-filters (the usual answer). The sediment and carbon cartridges sit in front of the membrane precisely to catch the silt and muck in the incoming water. In Delhi — tanker deliveries, borewell supply, monsoon turbidity — they fill up fast. A clogged pre-filter chokes the flow reaching the membrane, so the whole system slows. Changing the pre-filters on schedule is the highest-return maintenance on an RO here, and a slow trickle is the classic sign they are overdue.
- A tired or scaled membrane. The membrane is the fine barrier that actually removes dissolved salts, and over time — especially on hard, high-TDS water fed through neglected pre-filters — it fouls and its output drops. A membrane that is genuinely spent gives slow flow and often a change in taste together. But it should be ruled in only after the pre-filters have been changed, because a choked pre-filter mimics a dead membrane exactly and costs a fraction as much.
- A weak tank or low tank pressure. The stored-water tank uses air pressure to push water to the tap. If that has bled off, the flow at the tap weakens even when the tank has water in it. A technician can check and restore it.
The order matters, because it is also the order of cost. Fresh pre-filters first; membrane only if the slow flow survives the filter change. Anyone who quotes you a membrane before looking at the pre-filters is skipping the cheap answer.
Water tastes or smells off
The RO runs and fills, but the water tastes flat, salty, metallic, or smells faintly of chlorine or something stale. Taste is information — here is what it usually means.
- Carbon filter overdue. The activated-carbon cartridge is what strips chlorine, odours and that "off" edge. When it is exhausted, smells and tastes it used to remove start coming through. This is the first and cheapest thing to check for any taste complaint — it is a routine cartridge change.
- Membrane past its life. A salty, flat or "heavy" taste — water that no longer feels light the way RO water should — often means the membrane is letting dissolved salts through that it used to reject. If your water has quietly turned from crisp to flat over months, the membrane is the likely culprit. A technician can confirm it by measuring the TDS of the output (see the FAQ on sudden TDS jumps below).
- A stagnant or long-unused tank. Water that has sat in the storage tank for days — after a holiday, say — can taste stale. Drain the tank, let it refill fresh, and see if the taste clears before assuming a part has failed.
- Post-carbon / mineraliser stage spent. Many Delhi units add a final "taste" or mineral-adding cartridge after the membrane. When that is exhausted the water can taste flatter than you are used to. It is another inexpensive cartridge, not a machine fault.
Do not accept "the water is bad, replace the whole system." Taste problems are almost always a specific cartridge or the membrane — a targeted change, not a new purifier.
Water will not stop — overflow, or the pump keeps running
The opposite problem: the RO does not know when to quit. The tank overflows, water keeps trickling to the drain, or the pump runs on and on instead of clicking off when the tank is full.
- Faulty float valve or level switch (most common). The float is what tells the system the tank is full so it can shut off. When it sticks or fails, the RO keeps making water with nowhere to put it, so the tank overflows or water runs continuously to the drain. It is a small, inexpensive part and a common failure — the usual cause of a "won't stop" RO.
- Solenoid valve stuck open. Many systems use an electric shut-off (solenoid) valve that closes the inlet when the tank is full. If it jams open, water keeps flowing even after the machine is told to stop. Another modest part to replace.
- Constant drain trickle. An RO normally sends some reject water to the drain while it is producing — that is by design. But a steady flow to the drain even when the tank is full and the machine should be idle points back to the shut-off (float or solenoid) not closing properly.
A machine that will not stop is wasting water every hour it runs — worth attending to quickly in a city where water is not to be wasted. The good news is these are among the cheaper faults to fix.
Water leaking from the unit
You find water pooling under the RO, a damp patch on the wall or counter, or a steady drip from the body of the machine. Most RO leaks are undramatic and cheap to fix — the trick is telling a joint leak from a tank leak.
- A tube joint or push-fit connector (usual and minor). An RO is held together by many small push-in tube fittings, and over time one can loosen, or a tube can harden and crack — more so where hard-water scale builds up around the fittings. This is the commonest leak and a simple fix: reseat or replace the connector or the length of tube.
- A cartridge housing not seated or its O-ring gone. If the leak appears right after a filter change, a housing bowl that was not tightened properly, or a perished sealing ring, is the likely cause. Easy to correct.
- The pump or a valve seal. A leak from around the pump or a valve body points to a worn seal there — a technician's job, but still a component-level repair, not a write-off.
- A cracked storage tank. Less common, but if the tank body itself has split, that is a tank replacement rather than a patch. Get a technician to confirm the leak is really the tank and not a fitting on it before replacing anything.
First, safety and damage control: if water is pooling near the adaptor or the socket, switch the RO off at the wall before mopping up, and close the inlet tap to stop the flow. Then let someone identify which fitting is actually leaking — the fix is usually small once the source is found.
Need an Water Purifier & RO professional?
Get free quotes from independent, ID-verified professionals near you. XpertWorker never charges you — you pay the professional directly.
Get free quotes →Frequently asked questions
My RO stopped working after a power cut. What happened?
My RO is giving water very slowly. Is that normal?
Can I change the RO filters myself?
My water TDS suddenly went up. What does that mean?
My RO tank overflows and the machine will not switch off. Why?
Does XpertWorker set the price for RO repair in Delhi?
How we put this guide together
This guide is compiled from common Delhi NCR service patterns and reviewed by the XpertWorker team. XpertWorker connects you with independent, ID-verified professionals — we never charge you a paisa, and each professional sets their own price and quotes you free.