Dehumidifier running but not collecting water? What to check, in order
The short answer
Most dehumidifiers that run without collecting water are not broken. Check four things first: the tank is seated and not full, the target humidity has not already been reached, the room is warmer than about 18 °C, and the filter is clean. In a cool, air-conditioned UAE room, a small amount of water can be normal.
Is it a fault, or is the room already dry?
Start with a humidity reading, not with the machine. A dehumidifier only makes water when it cools air below its dew point. If the air is already fairly dry, there is little water left to take out.
The Stadler Form manuals for Albert, Lukas and Lukas Pro all say the same thing: the rated output is only reached from about 22 °C and 70% relative humidity. Most air-conditioned rooms in Dubai sit below that humidity once the AC has run for a while. So a 20 L/day unit will collect much less than 20 litres there. That is physics, not a fault.
Here is a hypothetical example. A 70 m² room with a 2.5 m ceiling holds 175 m³ of air. At 23 °C and 60% humidity, that air holds about 2.2 litres of water vapour in total. Bringing it down to 50% removes only about 0.36 litres from the air itself. More moisture comes from walls, furniture, people, cooking and air leaking in, but on a quiet day in a closed AC room the tank can fill slowly.
If you do not own one yet, a simple digital hygrometer is worth it. See should you measure humidity before buying a dehumidifier.
Quick checks: running but no water in the tank
Work down this table before you call anyone. The first rows are the most common and take a minute each.
| What you see | Likely cause | What to do |
|---|---|---|
| Tank full light on, unit stopped | Tank full, or not pushed fully home | Empty it and slide it back firmly. Albert and Lukas restart on their own once the tank is back in place. |
| Fan runs in short bursts, no water | Target humidity already reached | The hygrostat stops drying and briefly runs the fan to recheck. Lower the target, or set CO (continuous) for a test. |
| Fan runs, air feels the same, no water | Purify only mode (Lukas Pro) | In PURIFY mode alone, Lukas Pro cleans the air without dehumidifying. Press DRY. |
| Very little water at night | Night mode or lowest speed | Night mode on Lukas and Lukas Pro sets the lowest level. Raise the speed when the room is empty. |
| Hose fitted, tank empty | Water is going down the hose | Normal. Check the hose end, not the tank. |
| Little water, dusty filter | Clogged filter or grilles | Clean them. See how to clean a dehumidifier. |
| Little water, unit in a corner or behind a curtain | Blocked airflow | Leave at least 50 cm of space around it, as the manuals ask. |
| Little water, door or window open | Drying the whole building | ENERGY STAR advises closing doors and windows while it runs. |
| DEFROST shows, little water | Room too cold, or an AC vent blowing at it | Move it out of the cold draught. See the next section. |
| Nothing happens for a few minutes after restart | Compressor protection | Albert’s manual asks you to wait 3 to 5 minutes after switching off before switching on again. |
A timer can also catch people out. If a timer is set, the unit runs only for the hours you chose.
Cold AC rooms: the most common UAE cause
In the UAE, a dehumidifier usually runs next to air conditioning. That changes two things.
The AC already dries the air. As the AC cools, it removes some moisture. The colder the air, the less water a dehumidifier can pull out, because the dew point of the room drops. The table below shows this. Figures are calculated with the standard Magnus formula, not measured in a home.
| Room air | Dew point | Water vapour in each m³ of air |
|---|---|---|
| 30 °C, 80% (a humid, un-cooled room) | about 26 °C | about 24 g |
| 23 °C, 70% | about 17 °C | about 14 g |
| 23 °C, 60% | about 15 °C | about 12 g |
| 23 °C, 50% | about 12 °C | about 10 g |
| 18 °C, 60% | about 10 °C | about 9 g |
Cold air can frost the coils. ENERGY STAR says frost can form on the coils below about 18 °C (65 °F). The compressor then cycles on and off without removing much moisture. The Stadler Form manuals say the units work best between 13 °C and 35 °C, and that defrost runs too often at low temperatures. Albert runs in defrost mode automatically when the room is below 10 °C.
A room at 22 to 24 °C should not trigger frequent defrost. But a unit placed right under an AC vent, or a bedroom with the AC set very low, can feel much colder at the coils. Stadler Form UAE says that if Albert keeps showing defrost in an air-conditioned room at 18 to 24 °C, the sensor may be at fault and the unit should be checked.
For the full picture on capacity ratings, read what a 20 L/day rating means in an air-conditioned room.
A simple test: is it really drying?
- Close the doors and windows of the room.
- Move the unit away from walls, curtains and AC vents.
- Check the tank is empty and seated, or the hose is fitted correctly.
- Set the hygrostat to CO (continuous) and the fan to its highest level.
- After 10 to 15 minutes, hold your hand near the air outlet. A working compressor dehumidifier blows air that is a little warmer than the room. That heat comes from the compressor and the moisture it condenses. See does a dehumidifier make a room hotter.
- Note the room humidity on a hygrometer, then check it again after a few hours.
If the outlet air is warm and the humidity is falling, the unit is working. If the outlet air is the same temperature as the room, the room is above 60% and warmer than 18 °C, and the tank stays dry for hours on continuous mode, the compressor or a sensor may have a problem. That is a job for the service team.
Water on the floor, or a full tank with the hose fitted
Two related problems come up often in Google’s People also ask results for the UAE.
The tank fills even though the hose is attached. The hose works by gravity. Every Stadler Form manual says the end of the hose must be lower than the outlet on the unit, otherwise the water will not drain and can overflow. Check that the hose is not kinked, not running uphill, and not pushed too far into a drain where water can back up.
The unit runs but water ends up on the floor. Stadler Form UAE explains that after long use, or in a dusty room, the internal water outlet can block. Water then misses the tank and escapes underneath. Switch the unit off, check the tank and hose, and clean the water outlet as the manual describes. If it keeps happening, contact the service team.
More on choosing between the two: tank or drain hose.
How do you reset a dehumidifier?
The Albert, Lukas and Lukas Pro manuals do not describe a reset button. A safe power cycle works for most brands:
- Switch the unit off with its power button. Albert’s manual says not to pull the plug while it is running.
- Unplug it.
- Wait at least 3 to 5 minutes, so the compressor protection does not stop it restarting.
- Plug it back in, switch it on and set the mode, speed and target humidity again.
Lukas keeps its last settings after you switch off and unplug. Stadler Form UAE says Albert keeps its settings for 24 hours after a power cut. So a reset may not change a setting that is causing the problem. Check the settings by hand.
If you have just moved the unit, the manuals say to stand it upright and wait at least 60 minutes before switching it on.
When it is a real fault, and is it worth repairing?
Call the maker’s service team if:
- the outlet air is not warmer than the room after 15 minutes on continuous mode,
- it shows defrost in a warm room,
- it collects no water in a room you have measured above 60% and 22 °C,
- it smells of burning, gets much louder, or trips the power.
Do not open the housing. Albert, Lukas and Lukas Pro use R290, a flammable refrigerant. The manuals say only the maker’s authorised technicians may work on the refrigeration system, and improper repairs void the warranty.
Whether a repair is worth it depends mostly on the warranty. In the UAE, Stadler Form gives Albert and Lukas a 2-year warranty and Lukas Pro a 5-year Pro Series warranty, handled by its own service centre in Dubai. Inside the warranty, contact the seller first. Outside it, ask for a quote and compare it with the price of a new unit.
The opposite problem: the tank fills, but the room stays damp
If the unit collects plenty of water but the room still smells musty or reads above 60%, it may be too small, or the moisture keeps coming back from a leak, a damp wall or an open door.
- Check the size. ENERGY STAR advises that it is better to oversize than undersize. Our dehumidifier size calculator sizes by room volume.
- For a bedroom up to 70 m², the 20 L/day Stadler Form Albert has a built-in hygrostat with a 30 to 80% range and a 4.6-litre tank with automatic switch-off.
- For an open living area up to 175 m², Stadler Form Lukas Pro is rated at 50 L/day and has a 5.2-litre tank, a drain hose and a HEPA H11 filter.
If the damp keeps coming back and you cannot find the source, HawaQ’s indoor air quality testing logs humidity, temperature and air quality for two weeks in the rooms you use most, with an HVAC inspection, so you know what to fix first.
Disclosure: HawaQ, the indoor air quality team behind this site, supplies Stadler Form dehumidifiers and MedicAir air purifiers in the UAE. How we recommend.
Frequently asked questions
Why is my dehumidifier running but not collecting water?
Usually the tank is not seated, the target humidity has been reached, the unit is in purify only or night mode, or the room is too cool or already dry. Check those first. If the outlet air is not warmer than the room and a humid room stays humid, contact the service team.
Why is my dehumidifier collecting less water than before?
Common reasons are a dusty filter, a cooler room, a lower humidity in the room after the first days of drying, or doors left open. In the UAE, a cooler season or a colder AC setting also lowers output. Clean the filter and measure the humidity.
How do you reset a dehumidifier?
Switch it off with the power button, unplug it and wait at least 3 to 5 minutes before switching on again, so the compressor can restart. Then set the mode, speed and target humidity again. Many units remember their old settings, so check them by hand.
Why does my dehumidifier fill the tank when the hose is attached?
The hose drains by gravity. If its end is higher than the outlet on the unit, kinked, or blocked at the drain, the water cannot flow and stays in the unit. Lay the hose so it runs downhill all the way to the drain.
Is it normal for a dehumidifier to collect little water in an air-conditioned room?
Yes, often. The AC already removes moisture, and Stadler Form rates its units at 22 °C and 70% humidity or higher. In a room at about 23 °C and 50%, there is much less water in the air, so the tank fills slowly.
Is it worth repairing a dehumidifier?
Inside the warranty, yes: contact the seller or maker. In the UAE, Stadler Form gives 2 years on Albert and Lukas and 5 years on Lukas Pro. Outside the warranty, compare a repair quote with a new unit. Do not open it yourself: many use flammable R290 refrigerant.
Sources
- Stadler Form, Albert operating instructions (PDF). Operating range, rated conditions, hygrostat, defrost below 10 °C, tank full switch-off, restart wait, hose, repairs. Accessed 5 November 2026.
- Stadler Form, Lukas operating instructions and Lukas Pro operating instructions (PDF). Night mode, memory function, PURIFY mode, hose, R290. Accessed 5 November 2026.
- Stadler Form UAE, Albert and Lukas Pro product pages. Leak and defrost advice, settings after a power cut, warranty, specs. Accessed 5 November 2026.
- ENERGY STAR, Dehumidifiers. Frost below 65 °F, closed doors and windows, placement, sizing. Accessed 5 November 2026.
- HawaQ, Indoor air quality testing. Accessed 5 November 2026.