What is a nitrogen pressure test?

Nitrogen gas is pumped into isolated sections of the refrigerant piping at a controlled pressure. If the pressure holds, that section is leak-free. If it drops, the leak is in that section. It is a non-destructive way to locate leaks.

Do I need to hack walls to find a gas leak in a landed property?

Not necessarily. A nitrogen pressure test can narrow the leak to a specific section of the pipe run. If the leak is at the outdoor unit connections — which is common — no wall work is needed at all.

Are long pipe runs more prone to leaks?

The pipe run itself is generally robust. Leaks are more common at connection points — where pipes join the indoor or outdoor unit. The length of the run does not increase leak risk, but it does make finding the leak harder without proper testing.

LG Gas Leak on Landed Property With Long Pipe Run

Aircon case in Serangoon, Singapore: cooling loss traced to gas leak at outdoor unit pipe connections — concealed piping was intact after targeted diagnosis checks.

Case Details

Reported: My system 3 has been losing gas. The pipe runs from the outdoor unit at the back of the house through the wall to the indoor units upstairs. I am worried the leak is behind a wall and I will need to hack it open to fix it.
Unit: LG · Multi-split · 6 years old
Location: Landed · Serangoon, Singapore

What We Checked

Refrigerant pressure was below normal operating range across the system.
Pipe run extended from the outdoor unit at the rear of the house through concealed channels to three indoor units on the upper floor.
Outdoor unit pipe connections showed corrosion and green oxidation at the joints.
Nitrogen pressure test on the concealed pipe section held steady — no loss detected in the walls.
Nitrogen pressure test on the outdoor unit connections showed a drop, confirming the leak location.

The Diagnosis

The gas leak was at the outdoor unit pipe connections, not in the concealed piping. Corrosion at the outdoor connection joints had weakened the seal over time. The nitrogen pressure test confirmed the concealed pipe sections were intact, meaning no hacking was necessary. The long pipe run initially made the leak harder to locate because the homeowner and previous technicians assumed the length of pipe was the risk area, but the corrosion was confined to the exposed outdoor connections.

What Fixed It

We confirmed the concealed piping was not leaking and no wall work was needed. The leak was at the accessible outdoor connections. We welded the corroded joints and recharged the system. Because the outdoor unit was six years old and the corrosion was localised to the connection area, a weld repair was a reasonable first step before considering outdoor unit replacement. We recommended monitoring the welded area and scheduling an annual pressure check given the pipe length and property layout.

The leak at the outdoor connections was welded and the system recharged. Concealed piping remained untouched. Cooling returned across all three rooms with no gas loss detected at follow-up.

Why This Happens

How nitrogen pressure testing isolates leaks in long pipe runs.

Landed properties often have pipe runs extending through walls, ceilings, or outdoor channels. A gas leak could be at any point along the route.
Nitrogen pressure testing allows each section to be isolated and tested independently, narrowing the leak location without opening anything.
If the outdoor unit connections lose pressure while the concealed section holds, the leak is at the accessible outdoor end.
This approach can save significant cost by avoiding unnecessary hacking of walls or ceilings.

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