Why is my aircon leaking again after the drain was cleared?
A clearing that does not hold means the blockage was a symptom, not the fault. Something is putting water back where it does not belong. How long the fix lasted narrows what that something is.
By Team Snowflake | Updated 19 Aug 2026
1. A low point that refills after every clearing
A leak that comes back on a fairly regular interval after each clearing usually means the drain line dips somewhere along its run. That dip works as a trap. Flushing empties it, then water naturally pools there again and sludge rebuilds in the same spot until it backs up once more.
How to tell
This path is gravity refilling a trap. Unlike a crushed section, the return is tied to elapsed time rather than to heavy use. Unlike a cracked pipe, each clearing genuinely does stop the leak for a while.
- The leak returns on a fairly regular interval after each clearing.
- Clearing always works, and it always stops working.
- The drain run disappears into a false ceiling or a long concealed route.
- Nobody has ever explained why it keeps coming back.
How we confirm it
We trace the full drain route to find where it dips. The fall through that section is corrected so water cannot stand there between services.
Booking a clearing every time this returns misses the reason. The dip refills by gravity, so you pay twice a year for the same flush while the low point stays exactly where it is.
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2. A crushed section that only fails under heavy flow
A leak that returns on long or overnight runs, but behaves on ordinary days, points to a narrowed section rather than a blockage. A fixing screwed through trunking or a bracket pressing on the pipe can squash it out of round. That restriction still passes steady flow. It cannot pass the volume a long run produces.
How to tell
This path fails on volume rather than on time. Unlike a refilling low point, a clearing makes little difference and the trigger is a long run. Unlike a cracked pipe, ordinary short runs stay completely dry.
- It leaks after long or overnight runs, not on short ones.
- Ordinary days are fine, even soon after a clearing.
- Something was drilled or fixed near the trunking at some point.
- The leak volume relates to how hard the unit has been working.
How we confirm it
We locate the narrowed section along the run and relieve or replace that length of pipe. The unit then runs long enough to push full condensate volume through and confirm it clears.
Do not accept a repeat clearing for this. Flushing a crushed pipe changes nothing about its diameter, and the leak comes back the next time the unit runs long.
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3. A cracked pipe or joint below the tray
Water appearing lower down the trunking, with the indoor tray never overflowing, means the water is leaving the drain rather than backing up in it. An aged elbow or joint cracks at the bend. Water enters the drain normally, escapes at the damage, then runs inside the trunking and shows up further along.
How to tell
This path leaks out of the drain instead of backing up inside it. Unlike either blockage path, the clearing produced no improvement whatsoever. The tray drains normally, which is why the indoor unit never spills at the front.
- The indoor unit itself never overflows at the front.
- Water appears lower down the trunking, away from the unit.
- Clearing the drain changed nothing at all, not even briefly.
- The installation is old, or the trunking has been reworked.
How we confirm it
We open the trunking along the run and replace the cracked elbow or joint. The full route is then flushed to confirm water stays inside the pipe the whole way down.
Clearing a line that is not blocked does not fix a crack. If the tray has never overflowed, the blockage story is wrong and the pipe needs opening rather than flushing.
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