Repeated gas loss traced to outdoor pipe-joint leak
Aircon case in Pasir Ris, Singapore: cooling loss traced to refrigerant leak at outdoor unit pipe connection after targeted diagnosis checks.
Case details
What client reported
I've had the gas topped up twice now, maybe six months apart. It works for a bit then goes warm again. Two different technicians have looked at it — neither of them found a leak.
What we found
Two top-ups with no leak found usually means the checks weren't systematic. We started with a nitrogen pressure test to confirm the leak was still active, then worked through each connection in sequence.
- Refrigerant pressure below normal — confirmed low gas on arrival
- Nitrogen pressure test held for two hours — pressure dropped, confirming an active leak
- Indoor pipe connections checked with bubble solution — no leak visible
- Outdoor pipe connection at the service valve showed bubbles — leak confirmed there
The leak was at the pipe connection on the outdoor unit — specifically where the refrigerant pipe meets the service valve. It was a slow seep, not a fast loss. Previous technicians likely checked the indoor unit only, which is where most leaks are found. This one was further along the pipe.
What we did
The location was confirmed and the connection is fixable. We sealed the joint, re-ran the pressure test to confirm it held, then recharged the system. No further top-ups should be needed.
The outdoor connection was sealed and the system recharged. Cooling has held since — no further top-ups have been needed.
Timeline
Day 1
Unit not cooling — third top-up in less than a year with no leak location ever confirmed
Day 2
Applied bubble solution to each pipe connection in sequence — indoor first, then outdoor service valve
Day 2
Pressure test confirmed active leak; outdoor pipe connection found and sealed
What we learned
Why leak locations are sometimes missed.
- Leaks don't always show at the indoor unit — outdoor pipe connections are a common source
- Bubble solution needs to be applied to every connection, not just one end
- A nitrogen pressure test confirms whether a leak exists; checking each joint locates exactly where
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