LG Unit Topped up Twice: Corroded Outdoor Pipe Connections

Two top-ups in, and another one would restore cooling today. Whether to keep paying for gas or pay once to find where it goes.

By Team Snowflake | Updated 24 Aug 2026

Teaching case based on recurring Snowflake service patterns; identifying details are combined.

How this presents

Cooling that fades over a few months, is restored by having gas added, and fades again on a similar timescale. Each cycle is a little shorter than the last. The system is otherwise unremarkable and reasonably maintained.

Setup: LG Wall-mounted10-12 yearsHDBBukit Batok
Misread as: An expensive search that may find nothing, when another top-up would restore cooling today.
Check first: Whether the system has needed refrigerant added before

What else produces this

The repeat is the diagnosis. A sealed system that needs refrigerant twice has an opening somewhere, and the interval between top-ups is a rough measure of how large it is. That reframes the visit entirely: the useful work is finding where the loop is open, not restoring the pressure inside it. Outdoor connections are the first place to look, because they are exposed to weather, they carry joints, and they can be reached without opening anything.

A second top-up on the same system establishes a leak without any test being needed.
Shortening intervals between top-ups show the opening is growing rather than holding steady.
Traces at the outdoor pipe connections locate the escape at accessible joints.
Concealed pipework holding pressure when isolated keeps the repair to the outdoor end.

Why it happens

Joints at the outdoor unit sit in the weather and carry the vibration of a running compressor. Both work against a seal over the years. Once a joint begins to pass refrigerant, the loss is slow at first and accelerates as the gap opens, which is why the intervals between top-ups keep shortening. Nothing about the system is consuming refrigerant, and nothing about it ever was.

What resolution involves

The failed joints are made good and the system is charged properly afterwards, which is a repair rather than a postponement. The economics are worth putting plainly, because this is where households lose most. Repeated top-ups cost more across a couple of years than the repair does, and every one of them releases refrigerant into the atmosphere for no lasting benefit.

How to tell it worked

Pressure held over a period with the system isolated, rather than cooling that feels better on the day of the visit. A charge only proves the system is full right now, and whether it was full was never the question.

Before you approve a quote

Refrigerant is never used up, so low means gone

A sealed loop does not consume refrigerant. Needing more means some has escaped and is still escaping.
A second top-up is proof of a leak. No further test is required to establish that much.
Shortening intervals between top-ups mean the opening is growing. Waiting makes the repair no cheaper.

Questions this case answers

Is the compressor failing if the aircon needs topping up every few weeks?

No. Refrigerant circulates in a sealed loop and is not consumed like fuel, so a system that keeps needing more has a leak that will keep losing charge until the opening is closed.

Why do outdoor pipe joints corrode so fast here?

Because they sit outdoors. Weather, salt and compressor vibration act on the joints continuously, and moisture stays in a connection longer than on any surface that dries in open air.

What are the options once a leak is found at the outdoor connections?

The leaking joints are remade and the charge restored properly, which is a repair rather than another postponement. The traces here were at the accessible outdoor connections while the concealed pipework held pressure, so the work stayed at the outdoor end.

Is welding a corroded joint a permanent fix?

It can hold if the joint is properly made good: the failed joints here were repaired and the system charged, then verified by pressure held over a period with the system isolated. Repeated top-ups cost more across a couple of years and release refrigerant for no lasting benefit.

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