Gas leak returned after weld repair: corroded section too far gone
A welded gas leak came back within months. The new leak sat on the same corroded section, only centimetres from the first repair. The question was whether another weld could ever hold, or whether the pipe itself had run out of sound metal.
By Team Snowflake | Reviewed 19 Mar 2026
Case summary
LG Wall-mounted5 years oldHDBWoodlands, Singapore
- Concern
- The homeowner worried the first weld was wasted money, and that more costs would follow from chasing the same leak again and again
- Previous advice
- Previous contractor welded the leak and recharged refrigerant
- Found
- New refrigerant leak adjacent to previous weld on corroded pipe section
- Key check
- Bubble test showed active leak at a second point on the same corroded outdoor pipe, adjacent to the previous weld mark
- Result
- The outdoor unit was replaced with a compatible LG unit, while the existing indoor units were kept. The new connections were pressure-tested, the system recharged, and cooling has held steady since, with no further gas loss.
What we were told
The unit had been welded a couple of months earlier for a gas leak. Cooling returned for a while, then warm air and the error light came back. The homeowner asked whether they were paying again to fix the same fault.
What we checked
A weld repair followed by quick cooling loss points to a fresh leak, often near the old one. We checked gas pressure first to confirm a leak, then inspected the previous repair area closely.
Gas pressure was very low, so the system had lost refrigerant again.
The previous weld mark was visible on the outdoor unit gas line connection.
Green oxidation and surface pitting ran along the pipe on both sides of the weld.
A bubble test confirmed a fresh active leak about two centimetres from the old weld point.
LG error code CH35 was active, which the system raises on low-pressure protection.
What we found
The first weld sealed one leak point, but the corrosion underneath had spread along the pipe. The pitting reached well beyond the repair, so the metal was thin across a whole section, not just at the old gap. Heat from welding can also stress the nearby pipe wall. A new gap then opened a short distance away, where the wall had thinned the most. This is the usual outcome when a weld is placed on a pipe whose corrosion covers a stretch of the connection rather than one spot.
What fixed it
We explained that welding the new leak was possible, but the corrosion ran across the whole section. Another weld would carry the same risk of a third leak opening nearby within months. We recommended replacing the outdoor unit, which removes the corroded connections for good. The indoor units were still in good condition, so they could stay with a compatible outdoor unit. The homeowner weighed this against more weld-and-recharge cycles and approved the replacement.
Outcome
The outdoor unit was replaced with a compatible LG unit, while the existing indoor units were kept. The new connections were pressure-tested, the system recharged, and cooling has held steady since, with no further gas loss.
What this case teaches us
A weld fixes one spot, not a corroded pipe
- When a welded leak returns within months, the pipe surface is often corroded along a whole section, not just at one point.
- Welding a thinned, pitted pipe seals the gap but invites the next leak nearby. Each cycle costs gas, labour, and time.
- If a system was welded and recharged before, ask whether the corrosion is local or spread. That answer decides repair versus replacement.
Related reading
Ready to get started?
Tell us what’s going on. Symptoms, setup, photos, anything we should know. We’ll assess and come back with the right next step.