The pair coil problem

Around 2020, fridgies across Australia began reporting unusual leaks in the pair coil within air conditioning systems they had installed. Fixing these problems has proven costly, but should the technicians be the ones to pay the piper?

The problem

Pair coil is a type of copper piping with insulation on the outside that is commonly used in air conditioning. In recent years, installers of this type of piping have been called back to jobs by unhappy customers and finding small pinhole leaks in stretches of pipe where you wouldn’t normally expect them. Pipes have been corroding, systems have stopped working properly, and refrigerant has been exposed to the atmosphere in what appears to be classic cases of corrosion known as “ant nesting”.

According to the DCCEEW investigation, if the ends of the pair coil were not sealed properly and the bends were not done carefully, this could lead to moisture gathering between the insulation and the pipework, leading to corrosion.

Wholesalers claimed they had tested the pair coil and found that it was okay. Contractors did not all agree.

Leaking at the coal face

It’s all been a bit of a nightmare for Daniel Nigro, a fridgie of some 12 years and director of All Round Heating & Cooling in metropolitan Melbourne.

According to Nigro, the issue first raised its ugly head in 2022, with the ant nesting occurring between bends. Since then he’s had another 24 cases, but says they have been less frequent of late. Like many others in his field, he associates the problem with the COVID-19 pandemic.

“Something changed around then,” Nigro says. “Pipes started corroding, with small pinholes that you can’t see, and this generally happens when moisture pools in low points or where there is a bend in the pipe.

“The pipe turns a green purple, generally within two years of the install date. I’ve had a job where it happened within three months.”

Nigro found using cable ties to seal ends has helped, but like other fridgies, the cost of rectifying the leaks has fallen to him.

“I’m bearing the cost labour wise, but luckily I have a branch manager who has been very supportive in helping me out where he can.”

In addition to cable-tying the ends of all installations, Nigro also siliconed the insulation on all ducted jobs where moisture can pool on the U-bend, and he hasn’t noticed any issue since.

“It’s been very time consuming,” he says. “There’s also a lot of paperwork to do to fix these issues. I write everything down just in case any class actions do occur. And it’s been very frustrating trying to explain this to customers.”

Common concerns

Many other installers echo Nigro’s comments, voicing their opinions loudly on the “Crappy Refrigeration” Facebook page.

One says he has also been dealing with the problem since 2020, having had to rectify “well over 50 cases now and still going”.

Another fridgie reported 16 cases over the past two years, generally about a year after installation. He no longer uses white insulated pair coil because of this. “It has cost thousands to rectify and no one has any answers or accepts liability for this,” he says.

In his opinion, it is the insulation that is causing the issue. Even after joining new pipe, “pinholes on the liquid line and green corrosion” occurred just 12 months later, with the insulation then resembling jelly, he says. “There was possibly something they couldn’t get through COVID so they substituted it with something else.”

Another installer observes: “It always [occurs] in the same spot [in a bend at rear of outdoor unit]. It’s a massive issue.”

“All leaks are on the liquid line and not related at all to poor installation practices. I suspect poor quality copper imported through COVID. [I am told] there are only a handful of cases throughout Australia, but my fear is that many companies are yet to find their failed copper runs.”

Another company reports having its first issue with this on an install done almost five years ago. “The copper split. A tech [from a major company] claims this is happening very frequently and says it’s not due to poor installation but the quality of pair coil.”

Causes of corrosion

Martin Lynch, Affil.AIRAH, is a former mining professional who has managed a renewable energy business for the past 15 years. He is currently undertaking a PhD at the University of Queensland focusing on substitutes for copper.

Lynch notes that pinpointing the chemical reactions behind the ant nesting issue is key to working out who or what is at fault.

“There have been some suggestions that formicary corrosion is the problem,” Lynch says. “But this is a type of corrosion that occurs when a copper pipe is exposed to the air, and airborne chemicals – such as wood smoke or fumes from cleaning fluids – collect on the pipe surface. In the presence of water and oxygen these chemicals break down to formic or acetic acid, and they eat into the pipe. As these cases of corroded sections of pipe are not exposed to the air, it is very unlikely to be formicary corrosion.”

Lynch suggests that the problem is also probably not due to internal corrosion – which can be caused by refrigerant breaking down in the presence of moisture to form hydrofluoric acid – because the first-hand observations all say that the corrosion is forming on the outside of the pipe. This, then, suggests that it is general pitting.

“In the meantime, preventing any water ingress between the pipe and the insulation seems like a good preventive measure.”

DCCEEW findings

In 2023, the DCCEEW convened two advisory group workshops with industry peak bodies including suppliers, installers, and other experts on the concerns of leaking pair coil. The ACCC attended the advisory group to highlight the rights of technicians as consumers.

The DCCEEW also conducted an industry survey on pair coil issues, including questions on pair coil brand and specific issues observed. The survey results showed technicians had concerns with a range of different types of pair coil on the market, with no one brand or style of pair coil identified as more at fault.

Following the workshops, the advisory group recommended that pair coil issues were deemed to be a contractual issue best raised with the manufacturer of the pair coil.

In 2024–25, the DCCEEW worked with AIRAH to review, update and publish parts 1 and 2 of the Australia and New Zealand Refrigerant Handling Codes of Practice. This included providing more detail on best practice for pipework installation and maintenance.

Ongoing frustration

While the issue continues to cause problem, no action has been taken to independently test products or recall them if they were found to be faulty. Many HVAC&R contractors are still encountering problems – and bearing the financial burden of the issue.

Lynch says he would be cautious about laying the blame for ant nesting on poor installation practices given how many experienced installers have reported that they had not seen this type of corrosion prior to 2020. The fact that these issues have emerged post-2020 suggests that something else may have changed, he says.

Nigro disagrees strongly with the findings of the DCCEEW.

“Pair coil has been around for a very long time with no issues ever occurring,” he says. 

“I’m not sure whether it’s the copper itself or the insulation causing it, but it’s not an installation fault.”

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