Ceiling drip only on humid afternoons: hidden gap in the drain pipe
The unit dripped only on humid afternoons. A contractor had already replaced part of the drain, but the leak came back. The real source was a hidden joint further upstream, behind a ceiling panel.
By Team Snowflake | Reviewed 10 Mar 2026
Case summary
Daikin Ceiling10 years oldOfficeMarina South, Singapore
- Concern
- A drain replacement had already been paid for without fixing the leak, and the worry was that the whole run now needed redoing.
- Found
- Hairline gap at a concealed drain pipe joint behind the ceiling panel allowing intermittent drip under high humidity load
- Key check
- Traced the drain run behind the ceiling panel joint by joint to locate the leak source. Did not rely on replacing the visible drain section alone
- Result
- The intermittent drip stopped. The unit has since run through several humid days with no return, and no ceiling work beyond the one access panel. The result was a single joint repaired, not the full drain replacement they had been told to expect.
What we were told
Drips appeared near the unit, but only on humid days. A contractor had replaced part of the drain pipe a few weeks earlier, yet the drip returned. The latest advice was that the whole drain run might need replacing.
What we checked
When a drip returns after a partial drain replacement, the source is almost always elsewhere on the run, upstream of the part already fixed. We traced the full path from the unit outward, including the concealed section behind the ceiling panel that the earlier repair never opened. Dripping only on humid days was the clue: the gap was small enough that normal drainage passed it, but heavy humid-day flow did not.
The replaced drain section was intact and sealed. The earlier work was done correctly; the fault was simply not there.
Staining on the ceiling tile pointed to a drip origin further upstream from the replaced section.
With the ceiling panel opened, one concealed joint was found separated by about two millimetres, visible under a torch.
Pouring measured water through the drain reproduced the leak at that joint at humid-day flow rates, confirming the source.
What we found
The concealed joint had crept apart by about two millimetres over the unit's ten years. Drain joints are glued at installation, and the daily warming and cooling of the pipe slowly works that bond loose. On ordinary days the light drain flow passed the small gap. On humid days the unit pulled far more moisture from the air, so the drain ran fuller, backed up at the gap, and dripped onto the ceiling tile. The earlier contractor had replaced only the visible downstream section, which was sound; the real leak sat upstream, behind the panel.
What fixed it
We cleaned both faces of the joint, applied fresh cement, reassembled it, and held it while it cured. With the panel still open, we checked every other concealed joint on the run, and all were sound. We then ran the unit at full cooling and maximum fan to force peak drain flow. The ceiling tile stayed dry, and no other section needed replacing.
Outcome
The intermittent drip stopped. The unit has since run through several humid days with no return, and no ceiling work beyond the one access panel. The result was a single joint repaired, not the full drain replacement they had been told to expect.
What this case teaches us
A leak that returns after a repair is usually somewhere else
- When a drip returns after part of the drain was replaced, the new section is rarely the fault. The source is usually further along the run, often in a concealed stretch the first repair never opened.
- A leak that shows only on humid days points to a small gap: normal drainage clears it, but heavy condensate does not.
- Send a photo of where the water appears and note when it happens, before anyone quotes a full drain replacement.
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