Older condo trunking drip: insulation gap on a cold pipe
A Newton condo had water marks along the trunking after long cooling sessions. The drain was an obvious suspect, but older condo pipe routes can also sweat when cold pipes are exposed inside the trunking.
By Team Snowflake | Updated 28 Jul 2026
Case summary
Panasonic Wall-mounted10 years oldCondoNewton, Singapore
- Concern
- Owner expected drain replacement because water appeared along the trunking.
- Found
- Pipe insulation gap causing condensation inside trunking
- Key check
- Opened the trunking and checked the cold pipe before drain replacement
- Result
- The damp mark did not return during the test run after the exposed pipe section was sealed. The owner avoided replacing a drain that was still working and had a better way to describe any future water mark. That protects the next diagnosis from starting at the wrong section.
What we were told
The bedroom cooled normally, but water marks appeared along a trunking run after overnight use. The owner had been told the drain might need replacement. There was no obvious drip from the indoor unit itself, only dampness along the covered pipe route.
What we checked
We checked where the water started instead of assuming every trunking drip was a drain fault. The indoor tray, drain outlet, trunking route, and cold pipe insulation were inspected in order. The pattern mattered because the water appeared after long runtime, not immediately when the unit started.
The indoor drain left water normally during testing.
The damp section started along the trunking, not at the unit casing.
A small section of insulation had opened around the cold pipe.
Moisture formed on the exposed cold section after the unit ran.
What we found
The water was condensation from a cold pipe section inside the trunking. A gap in the insulation let humid room air reach the cold surface, so moisture formed and collected inside the cover. From outside, it looked like drain water because the mark followed the trunking. The drain path was not the main issue, which is why replacing the drain line would not have stopped the damp patch. The clue was that water started away from the unit casing and appeared only after the pipe had stayed cold.
What fixed it
We dried the area, corrected the insulation gap, and checked the drain path again before closing the trunking. The recommendation was a targeted insulation repair, not drain replacement. We also told the owner to watch whether future water appears only after long overnight cooling, because that timing is useful when separating condensation from active drain overflow. No gas work was needed because cooling was normal. The next service note should mention the repaired trunking section so the same spot can be checked first.
Outcome
The damp mark did not return during the test run after the exposed pipe section was sealed. The owner avoided replacing a drain that was still working and had a better way to describe any future water mark. That protects the next diagnosis from starting at the wrong section.
What this case teaches us
Trunking water is not always drain water
- Water along trunking can come from a drain leak, but it can also be pipe sweat if insulation has opened.
- Ask for the trunking to be opened at the wet section before approving drain replacement.
- Long runtime matters. Pipe condensation often appears after the line has stayed cold for some time.
Questions this case answers
Water marks along the aircon trunking: is the drain pipe leaking?
Why only after overnight cooling, and never after a short run?
Should the drain line be replaced when water shows up on the wall?
Does a wet trunking run mean the aircon needs gas or major repair?
Ready to get started?
Tell us what’s going on. Symptoms, setup, photos, anything we should know. We’ll assess and come back with the right next step.