RO Still Not Working After Service? 9 Causes and How to Fix Each One

Pearl Water Technologies Pvt Ltd. Last updated: 7 October 2026.

Quick answer: If your RO is still not working after a service, the cause is usually one of these: a closed valve or kinked tube, trapped air, low storage-tank pressure, a membrane or flow restrictor that was not replaced or does not match, a faulty auto shut-off valve, a failing electrical part, or low inlet water pressure. Check valves, tubing and the tank first. They take under 10 minutes and need no tools.

You paid for a service, the technician left, and the purifier is no better. Maybe it is slower, maybe it gives no water, maybe it now leaks. This happens more often than it should, and it does not always mean the service was bad. A service usually covers the filters. The fault often sits somewhere the filters never touch, like the tank, a valve, the pump or the incoming water pressure.

This guide is arranged from the quickest checks to the more involved ones, so you can work down the list before you call anyone.

What "not working" usually means: a symptom table

1. Is a valve closed, a tube kinked or a connector loose?

Start here, because it is the most common slip after any filter change. Check that the inlet ball valve is fully open, the tank valve is open, and no tube is bent sharply behind the unit. Push each quick-connect tube in firmly until it stops. A tube that looks seated can still be a few millimetres short.

For leaks, wipe each filter housing dry with tissue and watch where the first drop forms. If it is at a housing, unscrew it, check that the O-ring sits flat in its groove, and hand-tighten only. Over-tightening with a wrench cracks housings. Our step-by-step DIY filter kit installation guide shows the correct order for refitting.

2. Is there air trapped after the filter change?

A hissing or gurgling tap, or no flow right after the service, usually points to air in the lines. New cartridges and a fresh membrane let air into the system.

Let the tank fill completely, then open the tap fully and drain the tank until it is empty. Repeat once if the hissing continues. The first full tank after a service should not be drunk anyway.

3. Has the storage tank lost air pressure?

This one fools a lot of people. The tank has a rubber bladder with air on one side. That air is what pushes water to the tap. If the pressure is low, the tank can be full and the tap still barely runs.

To check, close the inlet valve, open the tap and drain the tank completely. Press a tyre gauge on the small valve on the tank. Many home RO tanks sit at roughly 6 to 8 psi when empty, but check your model's manual. If it is well below that, a bicycle pump will top it up. If it will not hold pressure, the bladder is leaking and the tank needs replacing.

4. Was the membrane not changed, or is it the wrong one?

Pre-filters are cheap and quick to swap, so they are what most services deliver. The membrane is the expensive part and the easiest to skip. If your output TDS is only slightly lower than your input TDS, or the tank takes much longer to fill than it used to, the membrane is the likely culprit.

Measure with a TDS meter: tap water first, then RO water from the tap. Our guide on what TDS should come out of your RO purifier explains how to read the numbers, and how the RO membrane removes TDS shows what is happening inside.

A new membrane can also cause low output if it does not match the system or is not flushed properly. See why a new RO membrane can produce less water than its rated GPD. If you are unsure whether yours is due, read how to know it's time to replace your RO membrane and how long an RO membrane lasts.

Check what was fitted, too. Our guide on how to spot a fake or duplicate RO membrane covers the signs, and the RO filter kit compatibility guide covers fit. Genuine replacements are on our domestic RO membrane page.

5. Is the flow restrictor wrong or missing?

The flow restrictor (FR) is a small part on the drain line that controls how much reject water leaves the membrane. Too large and the unit wastes water and loses output. Too small and production drops. It should match the membrane, so use whatever the membrane maker or your original unit specifies. If the drain runs hard and the tank fills slowly, ask what FR was fitted. For ways to cut wastage, see how to save and reuse RO waste water.

6. Is the auto shut-off valve faulty?

The auto shut-off valve stops the incoming water once the tank is full. When it fails, you may see continuous drain water, or the purifier may not restart after you use water from the tank. A quick test: draw a few litres from the tap. If the unit still does not start, suspect the valve, or the power side covered next.

7. Is an electrical part failing?

Unplug the unit before touching anything. If the pump hums without moving water, or the unit shows no light and no sound, the usual suspects are the power adapter, the pump or the solenoid valve. These parts do not get replaced in a basic filter service.

Do not open the adapter casing yourself. Our RO Electrical Control Kit page lists what is included, so you can match it to your fault before ordering.

8. Is the incoming water pressure too low?

An RO membrane needs adequate feed pressure to push water through. If the inlet supply is weak, a perfectly serviced unit will still trickle. Check by running a nearby tap at the same time of day you normally use the RO. Low mains pressure is a common cause in upper floors and at peak hours. A booster pump is the usual fix. Read the benefits of an RO booster pump before you decide.

9. Do the new filters need flushing?

If the water smells or tastes odd just after the service, this is often normal. New carbon filters can release fine dust and need a few minutes of flushing, and the tank can hold stale water. Drain the first one or two tanks. If the taste stays, our post on why your water suddenly tastes different walks through the other causes, and what a carbon filter does explains why this stage matters.

A 10-minute checklist before you call the technician

1. Confirm the inlet valve and tank valve are fully open.
2. Look for kinked or loose tubes and wipe the housings to spot leaks.
3. Fill the tank, then drain it fully once to clear air.
4. Check the tank pressure with a tyre gauge.
5. Test tap TDS and RO TDS with a meter.
6. Note how long the tank takes to fill, and compare it to before the service.
7. Run a nearby tap to judge the inlet pressure.
8. Listen for the pump: humming, clicking or silence.

Write down what you find. It makes the next service call much shorter.

Did the service cover the right parts?

A service is not the same as a repair, and the invoice should say which parts were replaced and which were only cleaned. Ask for the old filters and check them against what was billed. Ask what was changed on the membrane side and the electrical side, not just the pre-filters. Our guide to after-sales service questions to ask when buying a water purifier lists questions worth asking, and our RO service page explains what we cover.

Which parts fix which problem?

Filter life depends heavily on your source water, so treat any schedule as a guide. When you should change the filters of your RO purifier explains how to judge it. If you are weighing one part against a full set, see RO filter kit vs individual filters.

You can also browse the full range on the RO filter kit page, or buy single stages from the sediment filter and carbon filter pages. Prices change, so confirm on the product page.

For persistent faults across several parts, an overall look at membrane problems and fixes can help, and if your water is very hard or high in TDS, see the best RO for high TDS water.

Short answers in Hinglish

RO service ke baad bhi pani kam aa raha hai? Pehle tank ka air pressure aur air lock check karein. Uske baad membrane aur flow restrictor dekhein.

RO ka tank full hai par tap se pani dheere aa raha hai? Zyada tar tank ka air pressure kam hota hai. Tank khali karke tyre gauge se pressure check karein.

RO service ke baad pani kadwa ya smell wala hai? Naye filters ko flush karna padta hai. Pehle ek-do tank ka pani drain kar dein.

Frequently asked questions

Why is my RO not working after service?
Common causes are a closed valve, trapped air, low tank pressure, an unchanged or mismatched membrane, a wrong flow restrictor, a faulty shut-off valve, a failing electrical part, or low inlet pressure. Check them in that order.

How long should an RO take to fill after service?
It varies by model, so compare it to your own unit before the service. If it now takes much longer, suspect clogged filters, low inlet pressure, tank pressure or an old membrane.

Is it normal for RO water to taste odd after changing filters?
Briefly, yes. New carbon filters need flushing. Drain the first one or two tanks. If the taste or smell stays, look at the tank and the other causes above.

Can a new membrane cause low flow?
It can, if the membrane does not match the system, was not flushed, or the flow restrictor is wrong. Verify the rating against your unit's specification.

Should the membrane be changed at every service?
No. Change it when output and TDS readings show it is worn. Changing it too early wastes money; leaving it too long lets TDS creep up.

How do I know the technician replaced the right parts?
Ask for the old parts and an itemised bill. Take tap and RO TDS readings yourself, before and after.

When should I call a technician?
Call one if the tank will not hold pressure, the pump will not run, the unit leaks after you have refitted the housings, or you cannot find the fault after the checklist.

Need help?

Pearl Water Technologies Pvt Ltd supplies RO filter kits, membranes and spares from Gurugram, Bengaluru and Lucknow. Call the toll-free line on (+91) 9582215137 or message us on WhatsApp at 8588022991. Tell us your purifier model and what you see, and we will point you to the right part.

Safety note: always unplug the purifier and close the inlet valve before touching internal parts. Do not open electrical adapters.