Landed home drip traced to drain pipe gradient lost over time
Aircon case in Upper Thomson, Singapore: water leakage traced to drain pipe had sagged at a section along its run, creating a low point where condensate pooled and overflowed back toward the indoor unit on high-humidity days after targeted diagnosis checks.
Case details
What client reported
The living room aircon has been dripping on and off for the past few months. It only happens on really humid days. On dry days it is completely fine. The house is old and the pipes run through the wall. We are worried the drain pipe has cracked inside the wall and the whole thing will need to be hacked open to replace.
What we found
Intermittent dripping that correlates with humidity suggests the drain can handle normal condensate volume but overflows when the load increases. We traced the drain pipe run to check for gradient problems before assuming a crack.
- Drain pipe had a visible sag at a section where the support bracket had shifted away from the wall
- Water was pooling in the sagged section — the low point held standing water even when the unit was off
- On humid days the condensate volume exceeded what could trickle past the sag, causing water to back up toward the indoor unit
- After resupporting the pipe and restoring the downward gradient, water flowed freely through the entire run with no pooling
Over many years the pipe support bracket at one section had gradually shifted, allowing the drain pipe to sag and form a low point. Condensate pooled in that section. On normal days the volume was low enough to pass through slowly. On humid days the higher condensate volume backed up at the pool and overflowed back toward the unit, dripping from the indoor housing.
What we did
GOOD NEWS — the drain pipe was not cracked. A section had sagged from a shifted bracket, creating a low point that caused overflow on humid days. We resupported the pipe to restore a continuous downward slope. No hacking, no pipe replacement, and no wall work was needed.
The intermittent dripping stopped. The pipe now drains freely on both dry and humid days. The wall was not touched and the original drain pipe remains in service. The client avoided unnecessary hacking and pipe replacement.
Timeline
Day 1
Intermittent dripping on humid days — feared cracked drain pipe inside the wall
Day 1
Traced the full drain pipe run and checked the gradient at each support point before assuming the pipe was cracked
Day 1
Sagged pipe section resupported — gradient restored and dripping stopped
What we learned
Why older homes develop intermittent drips — drain gradient.
- Aircon drain pipes rely on a continuous downward slope to carry condensate away from the unit. Over many years, pipe supports can shift, brackets can loosen, and sections of pipe can sag. Even a small sag creates a low point where water pools.
- On normal days the condensate volume is low enough to trickle past the sag. On humid days the evaporator produces much more condensate. The pooled water backs up past the low point and overflows toward the indoor unit. This produces an intermittent drip that comes and goes with the weather.
- Resupporting the pipe to restore a consistent downward gradient fixes the drip without any pipe replacement or wall hacking.
Best next step
If your unit is behaving similarly, start with the service path that fits this case before approving broader scope.
Common questions
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