Bedroom leaked after servicing: drain joint left slightly loose
Water showed up the same evening after a routine service. That timing was the clue. A leak that starts right after work points back to the drain path that was just taken apart and put together. We treated it as a workmanship follow-up, not a new hidden failure.
By Team Snowflake | Reviewed 14 Jun 2026
Case summary
Mitsubishi Electric Wall-mounted8 years oldHDBBukit Batok, Singapore
- Concern
- The worry was that the indoor drain tray had cracked during servicing and the whole fan coil needed opening up.
- Previous advice
- Client was worried the drain tray had cracked during servicing
- Found
- Drain joint not fully seated after reassembly
- Key check
- Ran water through the drain tray and watched the joint behind the cover before opening the trunking
- Result
- The leak stopped on the same visit with no parts replaced. The unit ran long enough to confirm normal drainage. For the homeowner, the point was knowing this was not a second major fault, just a small reassembly slip that could be checked, corrected, and proven on the spot.
What we were told
The bedroom aircon was serviced in the afternoon. By night, water was dripping from the right side of the indoor unit. It had not leaked at all before the service.
What we checked
Because the leak began right after servicing, we checked the parts just removed and refitted before looking deeper. Opening too much too quickly can turn a small slip into a bigger job. We wanted to see where the water escaped: before the drain hose, after it, or in the wall route. The first flush ran with the cover open so the joint, tray, and wall outlet could all be watched.
Filter and front cover were fitted correctly.
Drain tray was intact with no visible crack.
Water poured into the tray escaped at the drain joint behind the cover.
The trunking and wall outlet stayed dry, so the leak was local to the indoor unit.
What we found
The drain hose joint had not been seated fully after cleaning. When water collected in the tray, a little escaped at that loose joint instead of running into the drain hose. The tray and the concealed pipe run were both undamaged. The clue was that the drip came from the indoor unit almost at once, not after hours of water backing up in the pipe. A cracked tray or hidden choke would usually leave wider water marks, or keep returning after the joint was tested. Here the escape point was the same every flush and stayed local, which tied the fault to the joint just reassembled, not a hidden wall route.
What fixed it
We reseated the joint, secured it, and flushed the tray again while watching the same point. Water ran cleanly into the drain hose with no further drip. We did not quote a tray replacement, because the tray held water once the joint was seated. We left the trunking closed, because the wall outlet stayed dry through the flush. We asked the customer to run the unit normally that night and check the corner, since a real concealed leak would show again after longer cooling.
Outcome
The leak stopped on the same visit with no parts replaced. The unit ran long enough to confirm normal drainage. For the homeowner, the point was knowing this was not a second major fault, just a small reassembly slip that could be checked, corrected, and proven on the spot.
What this case teaches us
A leak that starts hours after servicing is usually a loose reassembly
- Timing narrows the cause. This unit was dry before the service and dripping by night, so the parts just removed and refitted were checked first.
- Watch where the water escapes before assuming the worst. Here it slipped out at the drain joint behind the cover, not a cracked tray, so no part was needed.
- Note when the first drip appeared and where. That timeline keeps a post-service follow-up fair and separates it from an older choke deeper in the pipe.
Related reading
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