Water purifier faults: low flow, leaks, bad taste, not filling, noise
The five complaints behind almost every RO call, what each symptom usually points to inside the unit, which you can fix at the tap, and which need a visit.
5 min read · Updated 19 August 2026
Almost every purifier call fits one of five complaints: the flow is weak, it is leaking, the water tastes or smells wrong, the tank will not fill, or the pump is making a new noise. Each symptom narrows the fault down before anyone opens the unit. Here is what each usually means, most likely first, and which you can deal with at the tap.
Low flow or a trickle
What it usually is: a choked sediment filter, then a choked carbon pre-filter. These catch everything the water brings — and on Nellore borewell or post-monsoon water that is a lot. The pump works harder, less water reaches the membrane, and the tap dribbles.
What else it can be: a fouled or scaled membrane (flow drops and TDS rises together); a tired booster pump; a blocked flow restrictor on the reject line; a kinked tube; a tank whose air bladder has lost its charge; low inlet pressure because the overhead tank is empty.
Quick check: is the inlet tap fully open and is there water in the overhead tank? Then look at the sediment candle if the housing is clear — brown means change it. Beyond that, the low water flow visit on our rate card — membrane flush and pump check — is ₹350, with any filter at MRP shown first.
Leaking
What it usually is: a push-fit fitting where the tube was not pushed in far enough, or was pulled at an angle. The second most common is a filter housing that was not tightened evenly after the last change, or an O-ring that has flattened.
What else it can be: a hairline crack in a housing from over-tightening; the float valve not shutting, so the tank overflows through the vent; the drain saddle on the reject line weeping; a cracked dispensing tap; condensation on a cold tank in a humid kitchen, which looks like a leak and is not.
Quick check: switch off at the socket, dry everything with a cloth, run it and watch where the first drop appears. A fitting you can push in firmly or a housing you can tighten by hand is a fix; anything else is the leaking visit at ₹350.
Foul taste or smell
What it usually is: exhausted carbon filters, or a film in the storage tank and dispensing tap. Water that sat a week while you were away is the classic trigger — the first litre out tastes stale because it is.
What else it can be: a sediment filter that has started to rot because it was left far past its life; a dead UV lamp allowing growth in the tank; the source water itself — a sulphur or iron taste from a borewell, or chlorine from a freshly dosed municipal line; a TDS controller set so high that it is blending in too much raw water.
Quick check: run out two full tanks and taste again. If it is still there, it is not stale water. Our foul taste and smell visit — a multi-stage deep flush, filter check and tank clean — is ₹299.
Tank not filling
What it usually is: no power reaching the unit. The small adapter has failed, the socket has tripped, or the plug is loose. Second: the inlet tap is closed or the overhead tank is empty.
What else it can be: a stuck float switch telling the unit the tank is full; a low-pressure switch that has opened; a failed inlet solenoid valve; a stopped pump; pre-filters blocked solid; a membrane scaled shut. A unit that is silent and dark is electrical; one that hums but never fills is flow.
Quick check: is the indicator light on? Is the tap open? Is water in the overhead tank? If all three are yes and nothing happens, switch off and book a visit — do not open the adapter or the pump housing.
Noisy pump
What it usually is: the pump running dry or sucking air because the inlet supply is low or intermittent — a very Nellore summer problem when the overhead tank runs out in the evening. The pump rattles or chatters instead of its usual hum.
What else it can be: the pump straining against a blocked membrane or pre-filter (a loud, strained hum); worn pump bearings (a grinding note that gets worse); the unit or a tube vibrating against the wall or the cabinet; a loose mounting screw.
Quick check: make sure the tank is full and the inlet is open, then listen again. If it quietens, it was air. If it grinds, switch it off and book — a pump run dry for long does not last.
A quick map
| Symptom | First suspect | Second suspect | Usually needs a visit? |
|---|---|---|---|
| Low flow | Sediment/carbon filter | Membrane, pump | Yes if filters are recent |
| Leaking | Push-fit joint | Housing, O-ring, float valve | If hand-tightening fails |
| Bad taste/smell | Carbon filters, tank film | Source water, UV lamp | Yes if two tanks do not clear it |
| Not filling | No power, tap closed | Float switch, solenoid, pump | Yes if power and water are present |
| Noisy pump | Air in line, dry running | Blocked filters, worn pump | Yes if it grinds |
What not to touch
Switch off at the socket before tightening anything. Do not open the adapter, the pump housing, or the UV chamber — the lamp runs on a high-voltage ballast and the light harms eyes and skin. Do not bypass the float switch or the pressure switch to "make it fill"; they stop the pump destroying itself.
Questions people ask
- Water comes out slowly but the pump is humming. What is wrong?
- Most often the sediment or carbon pre-filter is choked and the pump is pushing against it, or the membrane itself is fouled. Less often the booster pump has lost pressure, or the tank is fine but the post-carbon filter is blocked. New pre-filters fix the majority; if flow stays low after that, the membrane or pump is the next suspect.
- There is a puddle under the purifier every morning. Is that dangerous?
- It is a fault, not a danger, unless water is reaching the adapter or the socket — if it is, switch off at the socket now. The usual causes are a push-fit tube not seated fully, a cracked or loose filter housing, a worn O-ring, or the drain line backing up. Tighten what you can reach by hand, dry the area, and if it returns it needs a visit.
- The water has started to smell stale or earthy. Do I need new filters?
- Usually yes, plus a tank clean. A stale smell is either exhausted carbon filters or a film growing in the storage tank and on the dispensing tap, common after a holiday when water sat still. If the smell is rotten-egg or chemical it may be the source water, which is worth mentioning when you book.
- faults
- repair
- diagnosis
- troubleshooting
Keep reading
- Water Purifier
How often do RO filters really need changing in Nellore? Go by TDS
Sediment, carbon and membrane life depend on what goes in, not the calendar. A realistic filter schedule for borewell, municipal and tanker water in Nellore.
5 min read
- Water Purifier
Installing a water purifier: pressure, drain, power and where to put it
Where an RO goes and how it is plumbed decides half its faults. Inlet pressure, drain line, socket, wall or under-sink, and what a good installation leaves you.
5 min read
- Water Purifier
Monsoon in Nellore: how the water changes and what your RO needs
October to December brings silt, mixed-up sumps and contamination risk. What to watch in the purifier, how often to check the sediment filter, and tank hygiene.
4 min read