My purifier is doing something weird — troubleshooting by symptom

A purifier rarely fails all at once. What usually happens is smaller: it drips a little longer than before, a light blinks a colour you don't remember, or the water tastes faintly different. None of that comes with the manual you've long since lost, and searching the brand plus the fault gets you a call-centre script or a listicle covering everything except your actual problem.

This is organised the way people actually search it — by what you're seeing, not what's wrong inside the machine. Find your symptom, read what usually causes it, and know whether it's a five-minute fix or a technician call.

Constant noise or dripping from the tap

Some noise is normal. A storage-type purifier runs a small booster pump to refill the tank, and that pump hums or cycles audibly. What isn't normal is dripping after the tank is already full, or a pump running long past when it should shut off.

That points to the auto shut-off: the float or solenoid valve that cuts flow once the tank fills. Sediment or scale on the valve seat stops it sealing fully, so water keeps trickling through — common in units a few years old that haven't had the tank or valve cleaned.

• Confirm the tank isn't already full and the outlet tap is fully closed — both look like faults but aren't.
• Check the delivery tube isn't kinked; that alone can trick the shut-off into never triggering.
• Dripping past a few minutes on a confirmed-full tank needs a technician — a worn valve gets replaced, not adjusted.

Red or blinking indicator light

Indicator meanings differ by brand and model, but the logic is similar: a light usually signals a filter due for replacement, low input pressure, a full tank, or an internal fault like a tripped leak sensor.

The filter-change alert is usually a timer, not a sensor. It counts days or litres since the last reset rather than measuring whether the filter is actually exhausted. That cuts both ways: it can go off with life left in the filter, and won't catch one failing early because the input water was unusually turbid.

• Check the manual for what that colour or pattern means on your model, before anything else.
• After a genuine filter change, reset the alert using the documented sequence; it won't clear on its own.
• If it persists after a correct reset, or comes with a drop in output, treat it as a fault, not something to keep resetting.

Low output or slow flow

Almost always one of three things: a clogged pre-filter, a scaled reverse osmosis (RO) membrane, or low input pressure.

The sediment pre-filter clogs fastest, especially with turbid municipal or borewell supply — change it every 3-6 months, sooner if input water runs dirty. The membrane scales up gradually with hard water and needs replacing every 2-3 years; past that, flow drops even without a visible fault. Many homes also feed purifiers from an overhead gravity tank at pressure below what the pump is rated for, which the booster can only partly offset.

• Check whether pressure has dropped generally — other taps running weak too — and inspect tubing for kinks.
• Flow that was fine yesterday and bad today, nothing else changed, points to the pre-filter — cheapest to check first.
• A decline over months with no error light usually means the membrane — a technician job.

Water tastes off, salty, or flat

A working RO membrane rejects most dissolved salts along with the impurities — that's the point of reverse osmosis. Water that suddenly tastes salty, metallic, or different means the membrane likely isn't rejecting solids properly, or a carbon/mineral cartridge downstream is exhausted.

Water sitting unused in the tank for days can also pick up a flat, stale taste — a hygiene issue, not a filtration failure, and it usually clears after running the tap for a bit.

• With a total dissolved solids (TDS) meter, compare the reading to what this unit normally gives — a jump of more than a few tens of ppm is worth investigating.
• A one-off odd taste after days unused usually isn't a fault; a persistent change is.
• Salty or metallic taste that persists after flushing the tap points to the membrane — get it checked.

Leaking from the unit

Most leaks trace back to push-fit tube connectors, the weakest mechanical point in any RO system and the part most disturbed during a filter change. A connector not fully seated, or a tube nicked while reinstalling a housing, weeps slowly rather than failing outright — easy to miss until there's a puddle.

Less commonly, the leak is a cracked filter or membrane housing, from over-tightening, age-related stress on the plastic, or inlet pressure it wasn't rated for.

• Power down, release pressure, and hand-tighten every visible connector — no tools, which can overtighten and crack the fitting.
• A leak that reappears at the same spot after tightening means the tube or fitting needs replacing.
• A leak from the sealed housing body needs a technician — don't force a housing seal shut.

RO wasting too much water

Reject water isn't a malfunction — it's how RO works. A membrane can't just trap dissolved salts and stop; it has to carry them away in a separate stream or they'd cake onto it and ruin it within days. What matters isn't whether your purifier produces this waste stream, but how much.

Recovery rate is the term for that ratio — the share of input water that comes out as purified product rather than reject. At 60%, that's 0.6 litres purified and 0.4 rejected per litre fed in — roughly 0.7 litres wasted per litre purified. Older or poorly maintained units are commonly reported to reject 3-8 litres per litre purified.

That 60% figure is now a rule, not a guideline. The National Green Tribunal directed in 2019 that RO purifiers, wherever permitted, hit at least 60% recovery, with reject water reused for mopping and flushing rather than drained. That was formalised as the Bureau of Indian Standards' IS 16240:2023 specification, then made mandatory by the Water Purification System (Regulation of Use) Rules, 2023, in force from November 2024: units made or imported after that must carry a BIS conformance mark tied to IS 16240.

This covers new units, not one already in your kitchen, and the Supreme Court has separately stayed a related NGT proposal to ban RO use below 500 mg/L source TDS — still unsettled. An old unit isn't stuck wasting water forever, though: a technician can often improve its ratio by fitting a correctly sized flow restrictor on the reject line, alongside a membrane change.

• Rough check: collect reject and purified output separately over a fixed time and compare volumes — a gap well beyond 2 parts waste to 3 parts purified means the unit is running inefficiently.
• Reject water isn't for drinking (it concentrates dissolved solids) but works fine for mopping, flushing, or laundry — routing it there instead of the drain is the one fix most households can make today.