Water dripping from my indoor AC unit onto the wall — how do I stop it?
The indoor unit of my split AC has started dripping water — it's staining the wall below it. It's not constant, more when it's been running a while. Is this dangerous and what causes it?
4 answers
Not dangerous, but fix it before it damages the wall. Two usual causes:
- Blocked condensate drain line (most common). The indoor unit collects condensation in a pan that drains away through a pipe. In the UAE that pipe clogs with dust/algae, the pan overflows, and water comes out the front instead of draining. The fix is a drain-line flush — a technician clears it in minutes.
- Frozen coil melting. If your filters are filthy, the coil ices up, then melts and overwhelms the pan. Same symptom, different root cause — check the filters (see AC running but not cooling).
Switch the unit off to stop the dripping, clean/replace the filters, and book a drain flush. If it's a chilled-water FCU rather than a split, it's the same drain-pan story — see musty smell from chiller vents. If the drain pan and coil are clogged, AC coil and filter cleaning clears the blockage that backs the water up.
Had the exact wall stain. It was a blocked drain line full of gunk — flushed in 10 minutes and it's been dry since.
For anyone whose 'leak' is really a drainage/backup issue rather than a simple drip, there's a more detailed thread on when a condensate pump and its float switch are involved — useful if your unit is a concealed/ceiling one that can't gravity-drain, because then an overflow is a pump/float problem, not just a blocked drain.
One thing worth adding from the FM side, because it catches people out every summer: a drain that just about coped through the cooler months will often start overflowing in July and August, and everyone assumes something suddenly broke. Usually nothing broke, relative humidity is the reason. The more humid the air, the more water the indoor coil pulls out and dumps into the drain pan, so the condensate volume in peak summer is far higher than in winter. A pan and drain line half-clogged with dust and algae has enough spare capacity in mild weather but tips over the edge once the humidity load peaks. So if your 'leak' shows up mainly in the hottest, stickiest weeks, don't wait for a dramatic failure, get the drain line flushed and the pan cleared before summer rather than during it. It's a five-minute job when it's booked ahead and a soaked wall when it's an emergency.
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