Water Purifier Not Working? 10 Common Problems and How to Fix Them Yourself

Before You Call a Technician: Check These First

Most purifier service calls in Bangladesh are for problems that the owner could have diagnosed and fixed in under thirty minutes. Technician visits cost ৳500–৳1,500 plus the cost of any parts — often for issues as simple as a kinked tube, a closed valve, or a clogged pre-filter. This guide walks you through systematic troubleshooting before spending money on a service call.

Work through the problems in order — start with the simplest possible cause before assuming a complex failure.

Problem 1 — No Water or Very Slow Flow From the Purified Water Tap

This is the most common complaint. In the vast majority of cases, it is caused by one of the following:

Check 1 — Is the inlet water supply on?

Open your normal kitchen tap. If no water flows there either, the building supply is off — not your purifier's fault.

Check 2 — Is the purifier's inlet valve open?

The saddle valve on your cold water supply line has a handle. Ensure it is parallel to the pipe (open). If it is perpendicular, it is closed.

Check 3 — Is the storage tank ball valve open?

The valve on the tank connection tube should be parallel to the tube (open). A closed tank valve stops all flow to the tap.

Check 4 — Is the sediment pre-filter clogged?

Hold the pre-filter housing up to a light — if it is dark brown or visibly discoloured, the filter is severely clogged. Replace it (৳200–৳300). This is the most common cause of slow flow in Bangladesh due to high sediment loads.

Check 5 — Is the storage tank pressure too low?

Use a tyre pressure gauge on the Schrader valve at the tank base. It should read 7–8 PSI. If it reads zero, the bladder in the tank has failed and the tank needs replacement.

Check 6 — Is there a kinked tube anywhere?

Open the cabinet and trace every tube. A single kink stops flow completely. Straighten any kinks and secure with a tube clip.

Problem 2 — Purified Water Has a Bad Taste or Smell

Chlorine taste — carbon pre-filter or post-carbon filter is exhausted. Replace both.

Musty or earthy smell — biological growth in the storage tank or post-carbon filter. Sanitise the tank with a dilute food-grade hydrogen peroxide solution (follow purifier manufacturer's sanitisation procedure). Replace the post-carbon filter.

Metallic taste — check the pH of your purified water. RO water is often slightly acidic (pH 5.5–6.5) which can taste metallic. A mineraliser cartridge post-filter resolves this. Also inspect all metal fittings in contact with purified water for corrosion.

Rotten egg smell — hydrogen sulphide in your source water. A carbon filter and an RO membrane together address this. If the smell is in purified water from a system that was working before, the post-carbon filter may be exhausted.

Plastic taste (new purifier) — new purifiers require 2–3 full tank flushes before the water tastes normal. Manufacturing residue from new filter media causes this. Flush and discard the first two tanks completely.

Problem 3 — Purifier Running Continuously / Constant Drain Sound

You should hear the purifier running (pump and drain sound) for 1–3 hours as the tank fills after use. If it runs continuously without stopping, one of these is the cause:

Cause 1 — Tank bladder has failed: The rubber bladder inside the pressurised tank separates purified water from the pressurised air. When the bladder ruptures, air and water mix. Check tank pressure — zero PSI confirms bladder failure. Replace the tank.

Cause 2 — Tank pressure too low: Even without bladder failure, low pre-charge pressure (below 5 PSI) causes the tank to fill very slowly or not reach the pressure needed to trigger the auto shut-off valve. Recharge to 7–8 PSI with a bicycle pump or tyre inflator.

Cause 3 — Auto shut-off (ASO) valve failed: The ASO valve closes when tank pressure reaches the correct level, stopping purifier operation. A failed ASO valve stays open permanently. Replacing the ASO valve (৳300–৳600) fixes this.

Cause 4 — RO membrane is badly fouled: A severely scaled or clogged membrane produces water very slowly, so the tank never fills enough to trigger shut-off. Replace the membrane.

Problem 4 — Water Leaking From the Purifier

From a push-fit tube connection: Pull the tube out fully, inspect the end for cuts or damage, trim 5mm off the end with a clean cut, and push firmly back in until it bottoms out. Pull to confirm it is seated.

From a filter housing: The housing O-ring is missing, damaged or not seated correctly. Turn off water supply, open the housing, inspect the O-ring and relubricate with food-grade silicone grease. Tighten firmly — hand-tight plus a quarter turn with the housing wrench.

From the drain saddle: Tighten the clamp screws. If the hole drilled through the drain pipe has cracked the pipe, the saddle needs to be relocated to an undamaged section.

From the tank: A hairline crack in the tank body requires tank replacement. Do not attempt to seal with adhesive — the tank operates under pressure.

Problem 5 — UV Lamp Indicator Light Is Off or Flashing

Check the power connection first — the UV lamp transformer plugs into a standard outlet. Confirm power is present at the outlet with another device.

Check the lamp itself — UV lamps have a finite life. After 9,000–10,000 hours (12–14 months), many lamps reach end of life and the electronic controller detects insufficient output and shuts down. Replace the lamp.

Check the lamp sleeve (quartz tube) — the quartz sleeve surrounding the UV lamp must be clean and clear. Mineral deposits on the sleeve block UV transmission. Clean with dilute citric acid solution and a soft cloth, rinse thoroughly.

Check the flow sensor — some purifiers' UV lamp only activates when water is flowing (a safety interlock). A faulty flow sensor may prevent lamp activation. Replace the flow sensor.

Problem 6 — TDS of Purified Water Is Too High

Calculate your membrane rejection rate: (1 - purified TDS / source TDS) x 100

Most common cause of sudden TDS rise: Carbon pre-filter expired, allowing chlorine to reach and oxidise the RO membrane. Replace both the carbon filter and the membrane together.

Problem 7 — Loud Noise or Vibration From the Pump

A humming or vibrating noise is normal during purification. These sounds indicate problems:

• Loud rattling — a tube is vibrating against the cabinet wall. Secure tubes with cable ties or foam padding.
• Grinding or screeching — the pump motor bearings are failing. The pump needs replacement (৳1,500–৳4,000 depending on model).
• High-pitched whine — air in the system, often from a low-pressure water supply. A booster pump upstream resolves this.
• Banging when pump starts — water hammer from pressure surge. Install a pressure reducer on the inlet line.

Problem 8 — White Particles in Purified Water

White particles immediately after filter replacement are usually carbon fines from a new carbon block filter — harmless but unpleasant. Flush until they clear (usually within 30–60 minutes of running).

White flakes from an existing system indicate scaling — calcium carbonate flaking off a failing post-carbon filter or from inside the storage tank. Replace the post-carbon filter and sanitise the tank.

Problem 9 — Purifier Works But Very Slowly After a Power Cut

Power cuts cause the pump to stop mid-cycle. When power returns, a pressure surge can partially close the auto shut-off valve prematurely. Open the purified water tap fully for 60 seconds to drain tank pressure, then close — this resets the ASO valve and allows normal operation.

Problem 10 — Purifier Was Not Used for 2+ Weeks

Stagnant water in a purifier sitting idle for weeks develops microbial growth — both in the storage tank and within the filter housings. Before drinking from a purifier that has been idle:

1. Discard the entire tank of stored water
2. Replace the post-carbon filter if idle for more than one month
3. Run 3 full tank volumes of water through the system before drinking
4. Test TDS to verify the membrane is still functioning
5. For idle periods above 3 months, replace all pre-filters and sanitise the system

If in doubt after extended idle periods, contact your service provider for a full sanitisation service before relying on the water for drinking.