If your filter has started behaving oddly, the useful thing to know first is that a small number of causes account for nearly all of it, and that a fair proportion of what gets reported as a fault is not a fault at all. Slow flow, a taste that has crept back, a drip under the sink, a gurgle, cloudy water in the glass — each has a normal explanation and a less normal one, and telling them apart usually takes a few minutes and a torch rather than a technician.
This page goes through the symptoms one at a time: what each usually means, what you can sensibly check yourself, and the point at which it stops being worth poking at. It also covers the ones that look like the filter’s doing and are not, because those waste the most time. Nothing here involves taking a machine apart.
The flow has gone slow
By far the most common complaint, and in most kitchens it is the cartridges telling you they are full. A carbon or sediment cartridge collects what it takes out of the water, and as it fills, the water has to work harder to get through. Flow tails off gradually over weeks, which is why people rarely notice the decline and then notice the result.
On a reverse osmosis system the pattern is different and often misread. RO makes water slowly and stores it in a small pressurised tank, so the tap runs properly until the tank is empty and then trickles while it refills. A good jug, then a poor one, then a good one twenty minutes later is the system working as designed, not failing. What is not normal is a tank that never reaches a decent run at all.
What to check. Open your ordinary mixer tap: if the pressure is poor there too, the problem is the building’s supply rather than your filter, and it will often be a temporary one. Look under the sink for the small isolation valve feeding the filter and check nobody has left it part-closed after working in the cabinet — this happens far more than you would think, particularly after a dishwasher or waste-trap job. Then work out honestly when the cartridges were last changed; if it is beyond the schedule, that is your answer. Our piece on whether a filter reduces water pressure covers what is normal at each stage.
When to call. Building pressure is fine, the valve is fully open, the cartridges are recent, and it is still slow. On an RO system that points at the membrane or at the tank having lost its air pressure, and neither is a home job.
The taste has come back
Carbon does not wear out on a calendar. It works by capacity — it holds a certain quantity of chlorine and the compounds that come with it, and once it is saturated it stops working while looking precisely as it did on day one. There is no colour change, no smell from the housing and no warning light. The first sign is that the water tastes of something again, usually chlorine.
Two other explanations are worth ruling out first. If the building has recently had its tank cleaned, the load reaching your filter went up and the cartridge may have been used faster than its normal life. And more often than anyone admits, somebody has been filling the kettle from the mixer tap rather than the filter tap; they look similar from a metre away.
What to check. Taste a glass from the filter tap and one from the mixer tap side by side. If they taste the same, the cartridge is spent. If the filtered one is still noticeably cleaner but not as good as it was, you are near the end of the cartridge’s life rather than past it. Either way the schedule and what drives it are set out in how often to change a water filter in the UAE, and what happens if it is left is covered in what happens if you do not change it.
When to call. Cartridges were changed recently and the taste is still there after the system has been flushed through for a few minutes. That is worth looking at rather than living with.
A drip or a leak under the sink
A leak is alarming and is usually smaller than it feels. The overwhelming majority happen at a joint rather than in the machine itself — a push-fit connector that was disturbed, a housing seal that needs reseating, or the tubing to the tap catching on something stored in the cabinet.
What to check. Dry everything thoroughly, lay a sheet of dry kitchen paper underneath, and come back in an hour. Wet paper tells you exactly which joint is dripping, which is the single most useful thing you can hand a technician. If it is running rather than seeping, close the isolation valve on the feed so nothing can add to it while you wait.
What not to do is tighten anything. Filter housings and push-fit connectors seal on an O-ring or a collet, not on force, and over-tightening turns a slow drip into a cracked housing. There is no adjustment on these fittings that a spanner improves.
When to call. Any leak that comes back after being dried, any water standing at the base of the cabinet, and immediately if there is a chiller or any other powered unit down there. Water and a socket in the same cupboard is not a wait-and-see situation.
Noise
An RO system gurgles. Water going to drain while the membrane works and the periodic flush that keeps it clean both make a noise, and it comes and goes rather than running continuously — typically starting after you have drawn a large volume and stopping once the tank is full again. That is the machine working, and it is explained in our article on whether reverse osmosis wastes water.
A chiller hums, and cycles on and off as it maintains temperature. In summer it will run more often, because it is fighting a warmer cabinet.
When to call. A drain noise that never stops, including hours after anyone last used the tap, suggests a valve or restrictor is not closing and water is running away continuously. A knocking sound when the tap shuts, or a new noise that arrived suddenly and has not settled, is also worth reporting rather than getting used to.
Cloudy or milky water
Almost always dissolved air, and it is harmless. The giveaway is the way it clears: pour a glass, set it down, and watch it go clear from the bottom upwards within a minute or so as the tiny bubbles rise. Sediment does the opposite, settling to the bottom and leaving the top clear first.
Air is more common after any interruption to the supply, after cartridges have been changed, and on systems that have not been used for a few days. Running the tap for a minute or two usually resolves it.
When to call. Cloudiness that does not clear on standing, or anything visible in the glass, particularly after work on the building’s tank or pipework. That is material getting past the sediment stage and it wants looking at.
The water is not as cold as it was
Start with the question that settles half of these: do you actually have a chiller? A filter removes things from water, it does not change its temperature, and no arrangement of cartridges will cool a drop. If your kitchen has a filter and no chiller, the water is at tap temperature, and in this country that is warm year round — it was never cold, and nothing has broken. Our guide to getting cold water in Dubai explains what that actually takes.
If you do have a chiller and it has genuinely fallen off, the usual causes are heavy use outrunning the machine’s recovery time, ventilation blocked by things stored around it in the cabinet, or the ambient temperature under the sink climbing through summer. Clearing space around the unit so air can move is a reasonable thing to try. A chiller that runs constantly and still delivers warm water is a service matter.
The cartridges seem to need changing sooner than expected
Cartridge life is a quantity of water, not a length of time, so a stated life assumes an average household. A large family, or one that uses the filter tap for cooking, the kettle, the coffee machine and the pets, will reach that quantity sooner, and that is the system being used well rather than a defect. An older building whose tank and pipework contribute more sediment will shorten the pre-filter’s life in particular.
Things that look like the filter and are not
- Limescale in the kettle. If the kettle is filled from the mixer tap, the filter has nothing to do with it — the subject is covered in our piece on limescale in Dubai kitchens.
- White marks on glasses. That is the dishwasher and its rinse aid, not your drinking water.
- Dry-feeling skin or hair after a shower. An under-sink system serves one tap and is not connected to the bathroom at all.
- Low pressure everywhere in the flat. A building supply issue, and the filter is a bystander.
- A smell that turns out to be the drain. Run the water, then smell the glass away from the sink before blaming the tap.
Before you call
Five minutes of noting things down changes how quickly a visit resolves anything.
- When the cartridges were last changed, as accurately as you can.
- Whether the problem is only on the filter tap or on the mixer tap as well.
- Whether it is constant or intermittent, and what seems to bring it on.
- For a leak, which joint the dry paper found.
- A photograph of the unit under the sink, which tells a technician what to bring.
Most of what is on this page is ordinary wear arriving on schedule, and it is largely why an annual maintenance plan exists — the visits change the cartridges before the taste comes back and check the joints before a seep becomes a leak. But the checks above are worth doing either way, because knowing which of these you are looking at is useful before anyone comes out.