Practical guide · updated 2026-07

Air conditioner leaking water: causes and solutions

Dripping from the indoor unit? The 4 most common causes, what you can fix yourself, and when you need a refrigeration technician.

Water leaking from the indoor split unit is the most common summer fault — and in most cases it isn’t a serious breakdown: it’s condensation that can no longer drain away where it should.

What to do, in order

1
Switch it off and clean the filters

Clogged filters make the coil freeze up: when the ice melts, the water overflows from the tray. Open the front panel, take out the filters, wash them in lukewarm water, let them dry and refit them. It’s maintenance to do every 2-4 weeks in summer.

2
Check the condensate drain

The drain hose (usually running outside) can be blocked by dirt or insects, or have a reverse slope. If you see nothing dripping outside while the split leaks inside, a blockage is the most likely cause.

3
Notice WHEN it leaks

Leaks only on humid days at full power: probably excess condensation, normal within limits. Leaks all the time, even at low power: cracked tray, faulty condensate pump, or ice from a lack of refrigerant — you need a technician.

What NOT to do

  • Don’t keep using it while it drips onto sockets or furniture: water first, everything else after
  • Don’t pour water or compressed air into the hose from inside: you risk flooding the tray
  • Don’t remove the split’s casing beyond the filter panel unless you know what you’re touching

When you need a technician

If after cleaning the filters and checking the drain the leak continues, the remaining causes (condensate pump, tray, ice from low refrigerant) need tools and spare parts. The refrigeration technician diagnoses on site and fixes it in the same visit in most cases.

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Frequently asked questions

The air conditioner leaks water and doesn’t cool: is it the same cause?

Often yes: a lack of refrigerant makes the coil freeze (which then drips) AND reduces performance. In that case you need a refrigerant leak search and a recharge — cleaning the filters isn’t enough.

How much does it cost to fix a water leak on the split unit?

Clearing the drain or a deep clean generally stays under €120; a condensate pump or a gas recharge cost more. Always get a quote before the work.

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