Gas Leak Returned After Weld Repair: Corroded Section Too Far Gone

• •Concern: Worry was that the weld repair was wasted money and ongoing costs would follow from chasing the same leak
• •Previous advice: Previous contractor welded the leak and recharged refrigerant
• •Key check: Bubble test showed active leak at a second point on the same corroded outdoor pipe, adjacent to the previous weld mark

The history of a prior weld repair followed by rapid cooling loss pointed strongly to another leak on the same corroded section. We started with a visual inspection of the previous repair area.

• •Refrigerant pressure was significantly below operating range.
• •Previous weld mark was visible on the outdoor unit gas line connection.
• •Green oxidation and surface pitting extended along the pipe on both sides of the weld.
• •Bubble test confirmed a new active leak roughly two centimetres from the old weld point.
• •LG error code CH35 was active, consistent with low-pressure protection.

The original weld sealed one leak point, but the underlying corrosion had spread along the pipe surface. The corroded area extended well beyond the weld. Heat from the welding process may have also stressed the adjacent pipe material. A new gap opened nearby where the pipe wall had thinned from oxidation. This is a common pattern when welding is applied to pipes where corrosion is not localised to a single point but covers a section of the connection area.

We explained that welding the new leak was technically possible, but the corrosion pattern suggested the pipe section was broadly compromised. Another weld would carry the same risk of a third leak appearing nearby. We recommended replacing the outdoor unit to eliminate the corroded connections entirely. The indoor units were still in good condition and could be retained with a compatible replacement. Outdoor unit replacement was approved after weighing the risk of continued weld-and-recharge cycles.

The outdoor unit was replaced with a compatible LG unit while the existing indoor units were retained. The new connections were pressure-tested, the system recharged, and cooling has held steady with no further gas loss.

Why welding corroded outdoor pipes often fails long term.

• •Welding seals the active leak point, but the surrounding pipe surface may already be weakened by the same corrosion.
• •Heat from welding can stress adjacent corroded areas, sometimes triggering new leaks nearby.
• •If the corrosion covers a broad section of the pipe, replacement is more reliable than repeated welding.
• •A single weld repair is worth attempting when the corrosion is isolated. When it spreads across the connection area, the odds shift toward replacement.