HDB bedroom drip after years of use: drain choke behind trunking

A Tampines bedroom unit began dripping after years of normal use. The flat had older trunking and the leak appeared only after longer runtime. That made the drain route the first serious check, not the gas side.

By Team Snowflake | Updated 28 Jul 2026

Case summary

Panasonic Wall-mounted12 years oldHDBTampines, Singapore

Concern: Water near the trunking read to the homeowner as a cracked indoor tray.
Found: Drain choke behind the trunking causing water backup
Key check: Checked drain flow and the trunking route before blaming the unit tray
Result: The unit ran through a longer cooling cycle without dripping. The case avoided a tray replacement and left a clearer sign to watch: slow drain flow at the trunking route after overnight use or longer afternoon cooling.

What we were told

The bedroom aircon dripped after running through the night. Short use did not always show the leak. Water appeared near the trunking, and the suspected issue was a cracked indoor tray after years of use. The intermittent timing made a quick visual check unreliable.

What we checked

A leak that appears after longer runtime often means water is slowly backing up. We checked the indoor pan, then tested the drain flow through the trunking route. The older route mattered because a small choke can hold enough water to overflow only after sustained cooling.

The pan was not visibly cracked.
Drain flow was slow when water was introduced.
Sludge was lodged behind a trunking section.
The leak point matched where water collected during the drain test.

What we found

The drain line was choked behind the trunking. Water left the indoor unit, then slowed at the hidden section and backed up during longer operation. Because the issue took time to show, quick on-off testing could make the unit look fine. The fault was drainage, not a gas problem and not proof that the indoor tray had failed. The mature HDB route simply needed to be opened enough to clear the blockage and confirm flow. The first wet point also showed that water was escaping after it entered the drain route, not before.

What fixed it

We cleared the choke, flushed the drain route, and ran water through it until flow was steady. We also explained which wet point to watch if the issue returned. If future leakage appears at a different section, the next step would be tracing the remaining route, not assuming the same choke. For this visit, the correct scope was drain clearing and route confirmation, not replacing the indoor unit. That kept the repair proportional to what the drain test actually showed.

Outcome

The unit ran through a longer cooling cycle without dripping. The case avoided a tray replacement and left a clearer sign to watch: slow drain flow at the trunking route after overnight use or longer afternoon cooling.

What this case teaches us

Older HDB leaks often need the drain route checked, not just the unit front

Water can back up from a hidden drain choke even when the indoor tray is intact.
In mature estates, older trunking routes may hide low points, sludge, or old joints that only show up after longer runtime.
Before accepting a tray or unit replacement, ask whether drain flow was checked through the full route.

Questions this case answers

Bedroom aircon drips after running all night but not during short use. Why?

Water is backing up somewhere in the route. In this 12-year-old Tampines flat the drain flow was slow when water was introduced, and sludge was lodged behind a section of trunking. Short sessions cleared themselves, while a full night produced more condensate than the restricted line could pass, and it escaped near the trunking.

Can a quick visual check confirm a drain problem?

Not with an intermittent leak. The pan was not visibly cracked, and switching the unit on and off briefly made everything look fine. What settled it was introducing water and watching the flow, which showed the restriction and matched the leak point to where water collected during the test.

Does an aircon dripping after twelve years mean it needs replacing?

Years of service do not make the tray the culprit. The fault here sat in the drain route, and the mature trunking simply needed opening enough to clear the blockage and confirm flow afterwards. Replacing a working indoor unit would have carried the same choke into the new installation.

If the leak comes back, what is the sign to watch for?

Slow drain flow after overnight use or a long afternoon session, and where the first wet mark appears. If water shows up at a different section next time, the remaining route gets traced rather than the same spot cleared again. That detail keeps the next visit proportional to the actual problem.

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Tell us what’s going on. Symptoms, setup, photos, anything we should know. We’ll assess and come back with the right next step.

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