Older Condo Trunking Drip: Insulation Gap on a Cold Pipe

Water marks appearing along a trunking run after overnight cooling, with nothing dripping from the unit itself. The room cools normally. Short runs produce nothing at all, and the dampness follows the covered pipe route rather than starting at the casing.

Where the water starts is the whole question, and it is answerable by looking rather than by reasoning. Drain water leaves the unit and travels. Condensation forms wherever a cold surface meets humid air, which can be metres from the casing. The second clue is time: a drain overflows as soon as volume exceeds the path, while a cold pipe needs hours to chill enough to sweat.

Refrigerant pipe runs cold whenever the unit is working, and insulation is what keeps humid room air off it. A gap lets that air reach the metal, and moisture condenses on it exactly as it does on a cold glass. Inside a trunking cover the water has nowhere to go but along the run, which is why it reads as a leaking drain to anyone looking at the outside.

Close the insulation gap and dry the cover, which is a targeted repair rather than a pipe replacement. Checking the drain path anyway before closing up costs nothing and settles the other half of the question. The observation worth handing over is the timing: water only after long cooling is condensation, water at any runtime is drainage, and that one sentence saves the next person the same trace.