LG system-3 losing gas: leak outdoors, not inside walls

On a landed property, the pipe run between indoor and outdoor units can be long, so a leak could sit anywhere along it. The homeowner feared the worst: a leak behind a wall, with hacking to reach it. A pressure test told a different story.

By Team Snowflake | Updated 28 Jul 2026

Case summary

LG Multi-split6 years oldLandedSerangoon, Singapore

Concern: The fear was that the leak sat in concealed piping behind walls, which would mean hacking and restoration to reach.
Found: Gas leak at outdoor unit pipe connections. Concealed piping was intact
Key check: pressure hold test on isolated pipe sections confirmed the concealed run held pressure while the outdoor unit connections lost pressure
Result: We welded the outdoor connections and recharged the system. The concealed piping stayed untouched, with no walls opened. Cooling returned across all three rooms, and the follow-up check found no further gas loss.

What we were told

The system 3 kept losing gas. The pipe run goes from the outdoor unit at the back of the house, through the wall, to indoor units upstairs. The homeowner worried the leak sat behind a wall and would need hacking to reach.

What we checked

The long pipe run meant the leak could sit anywhere along the route. We used a pressure hold test to narrow the location before recommending any work that opened walls.

Gas pressure read below normal across the system, which confirmed an active leak somewhere on the run.
The pipe run reached from the outdoor unit at the rear, through concealed channels, to three indoor units upstairs.
The outdoor unit pipe connections showed corrosion and green oxidation at the joints.
We held pressure on the concealed pipe section on its own. It stayed steady, so the buried run was ruled out.
We then held pressure on the outdoor unit connections. It dropped, which pinned the leak to the exposed joints.

What we found

The leak was at the outdoor unit pipe connections, not in the concealed piping. Corrosion at the outdoor joints had weakened the seal over time. The pressure test confirmed the buried sections were intact, so no hacking was needed. The long run had made the leak seem harder to find. It is easy to assume the length of pipe carries the risk, but the corrosion stayed at the exposed outdoor joints.

What fixed it

We confirmed the concealed piping was not leaking, so no wall work was needed. The leak sat at the accessible outdoor connections. We welded the corroded joints and recharged the system. The outdoor unit was six years old and the corrosion stayed at the connection area, so a weld repair was a fair first step before any talk of replacing the unit. Given the pipe length and the property layout, we advised monitoring the welded area and a yearly pressure check.

Outcome

We welded the outdoor connections and recharged the system. The concealed piping stayed untouched, with no walls opened. Cooling returned across all three rooms, and the follow-up check found no further gas loss.

What this case teaches us

A long pipe run does not mean the leak is hidden

A pressure test isolates the leak before any wall is opened. It can hold the concealed run separately and prove it is intact.
Most gas leaks start at the connection joints, where corrosion attacks the seal. The exposed outdoor links fail more often than the buried pipe.
Before agreeing to hacking, ask which sections held pressure and which dropped. The test points to the leak, so the repair stays where the fault is.

Questions this case answers

Does a gas leak in concealed piping mean hacking the walls?

Not before the leak has been located. On this Serangoon landed property the concealed run was held under pressure on its own and stayed steady, which cleared it. The outdoor connections were then held separately and the pressure dropped. No walls were opened and no restoration work was needed.

How is a leak located on a long pipe run without opening anything?

By isolating sections and holding pressure on each in turn. The run here went from the outdoor unit at the rear, through concealed channels, up to three indoor units. Testing the buried section separately from the exposed joints proved which one was losing pressure before any decision about opening a wall.

Where do refrigerant leaks usually start?

At the connection joints, where corrosion attacks the seal. Exposed outdoor links fail more often than buried pipe, because they sit in the weather while a concealed run is protected. That held true in this house: the outdoor joints showed corrosion and green oxidation while the buried piping was intact.

What should I ask before agreeing to hacking work for an aircon leak?

Which sections held pressure and which dropped. A pressure test gives that answer directly, and it keeps the repair where the fault is rather than where the pipe is longest. Length of run is not evidence of anything. Welding the joints and recharging settled it here, with the buried pipe untouched.

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