Older HDB trunking drip: perished gasket seal at the access panel

A Queenstown HDB room had water appearing along the trunking, not directly under the fan coil. In older flats, that detail matters. The leak can start at a sealed access panel instead of the visible indoor unit or its drain path.

By Team Snowflake | Updated 28 Jul 2026

Case summary

Daikin Wall-mounted15 years oldHDBQueenstown, Singapore

Concern: The homeowner thought the indoor unit tray might be cracked and replacement might be needed.
Found: Perished gasket seal at a trunking access panel, letting condensation escape at the panel seam
Key check: Traced the wet point to the access panel seam before opening any drain fitting
Result: The trunking stayed dry after the access panel was resealed and the seam was checked through a full cooling cycle. The homeowner avoided replacing a working indoor unit, and future leaks can be traced from the first wet point instead of guessing from the unit front.

What we were told

Water appeared along the bedroom trunking after the aircon ran for a while. The fan coil itself did not drip from the front edge, but the wall below the trunking became damp. The concern was a cracked tray.

What we checked

We started by finding the first wet point instead of opening the whole unit immediately. The water line began right at a trunking access panel, which suggested the panel's own seal was involved rather than the drain path itself. We removed only the necessary cover sections to avoid disturbing the older route more than needed.

The fan coil drain pan was not overflowing at the front edge.
The first visible wet point sat right at an access panel seam.
The panel's rubber gasket seal had perished and shrunk with age.
The drain coupling and pipe route behind the panel were still intact.

What we found

The trunking access panel's rubber gasket seal had perished and shrunk after years of use. Condensate collecting inside the trunking reached that shrunk seal and escaped through the gap at the panel seam itself, not through any drain fitting. That is why the symptom appeared away from the fan coil, which is why the tray looked suspicious at first. The drain coupling and pipe route behind the panel were sound, so the fault sat in the panel's seal, not the drainage path leaving the indoor unit.

What fixed it

We resealed the trunking access panel with a new gasket sized to the panel, then confirmed the seam sat flush before closing the cover. We explained that the repair had to follow the seal, not the most visible unit. The homeowner was advised to monitor the same access panel after a full cooling cycle. If water returned elsewhere, the next check would be the remaining trunking joints rather than a new indoor unit quote.

Outcome

The trunking stayed dry after the access panel was resealed and the seam was checked through a full cooling cycle. The homeowner avoided replacing a working indoor unit, and future leaks can be traced from the first wet point instead of guessing from the unit front.

What this case teaches us

Trunking leaks need the first wet point traced

Water at the trunking does not prove the indoor unit is leaking from its tray. An aged seal on the trunking itself can fail long before any drain fitting does.
Older Queenstown flats may still have original trunking covers with rubber seals that have hardened or shrunk with age. Those access panels should be checked before replacement is discussed.
Send photos of where the water first appears. That tells the technician whether to inspect the unit body, an access panel seal, or the drain path.

Questions this case answers

Water at the aircon trunking but not under the unit: where is it coming from?

Trace the first wet point. In this 15-year-old Queenstown flat the fan coil drain pan was not overflowing at the front edge, and the water line began right at a trunking access panel. The panel's rubber gasket had perished and shrunk with age, letting condensate escape through the gap at the seam.

Does a trunking leak mean the indoor tray has cracked?

It did not here, and that assumption very nearly cost a working indoor unit. The drain coupling and pipe route behind the panel were both sound. Because water showed up away from the fan coil, the tray looked suspicious until the wet point was traced back to the panel's own seal.

How old does trunking have to be before the seals give out?

There is no fixed point, but older flats still carrying their original covers are where hardened and shrunken rubber turns up. Age stiffens the gasket until it no longer sits flush at the seam. On this route the seal failed long before any drain fitting did, which is the opposite of what most people expect.

What photo helps most when reporting an aircon leak?

One showing where the water first appears, not just the puddle. That single detail decides whether the unit body, an access panel seal or the drain path gets opened first. Here it pointed at a seam, so only the necessary cover sections were removed and the older route was left otherwise undisturbed.

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