It is always important for the project team to carefully vet how new construction materials will be integrated into a project. Everyone wants the project to succeed, and no one likes surprises, but anxiety about the consequences of a project gone wrong looms in the background. In this litigious climate, the financial and emotional costs of litigation are high.
In the plumbing and mechanical heating, ventilation, and air conditioning (HVAC) sectors, the challenge of having to watch your back over the integration of new products is compounded by trending claims involving materials that are supposed to work, like copper pipes.
Environmental changes also add to uncertainty about how construction materials will perform. Yet, in the current environment, contractors and design professionals need to be even more diligent to mitigate their risks by taking steps to get better educated and making efforts to improve behaviors they can change. This article highlights emerging claim themes involving both legacy materials (such as copper) and newer systems (such as polypropylene) and offers practical due diligence questions to help reduce liability exposure.
Copper Pipes
As reported in a 2026 post on classaction.org, plaintiff class action counsel are looking for clients “plagued by a defect” in Mueller brand copper pipes, which connect interior and exterior components of ductless mini-split HVAC systems. The copper pipes, called line sets, run from the air handler unit mounted on the inside wall of a building to the condenser unit on the outside of the building. The copper pipes on the outside get wrapped in insulation jackets. In some situations, the technicians leave gaps in the insulation jackets, which allows moisture to become trapped under the insulation. Moisture can react with the insulation itself to create an acidic environment that corrodes the copper line sets. The acidic environment can lead to formicary corrosion, also called ant-nest corrosion, which creates microscopic pinhole leaks in the copper pipes. Formicary corrosion can result in the loss of refrigerant, causing the mini-split systems to run poorly or fail.
In other applications, lubricating oil or other fluids in the pipe manufacturing process can leave residual acids on the pipes, which can also cause corrosion. So, if pinhole leaks are discovered in copper pipes, are they the result of construction defects (improper installation of insulation?), manufacturing defects (acidic fluids or the use of improper insulation?), or both? We are likely to hear more about formicary corrosion as the class action lawyers continue to round up new clients, so be on the lookout.
Evaporator Coils
On a related note, the Sauder Schelkopf firm reports in a 2025 website post that it is investigating potential class action claims involving formicary corrosion within the evaporator coils in Carrier brand air conditioners. The evaporator coil is the component inside the air conditioner through which refrigerant is run to turn warm, humid air into cool, dry air. The kinds of refrigerant used in air conditioning systems have changed over the years for environmental reasons. For example, Freon (R-22) was typically used before 2010; it was replaced by Puron (R-410A), which was in common use up through 2024; and now the HVAC industry is moving to Puron Advance (R-454B) or Difluoromethane (R-32) to meet stricter environmental regulations, achieve higher energy efficiency, and lower global warming potential. The post describes allegations that certain Carrier air conditioning units with copper evaporator coils are prone to premature failure and refrigerant leaks when paired with newer, high-pressure refrigerants, leading to costly repairs or replacement. In contrast, the post says that aluminum coils withstand the higher operating pressures more effectively.
Similarly, a 2026 post on classaction.org reports that formicary corrosion is being investigated in evaporator coils in air conditioning systems sold under more than two dozen brand names. The post describes allegations that some of the targeted HVAC manufacturers misrepresented the quality of their air conditioning systems, and that some manufacturers deliberately misled consumers by selling products they knew to be defective. In addition to repair or replacement cost damages, the post describes losses involving higher energy costs.
The Atmosphere and the Water Supply
At times, the failure of pipe systems arises from causes that are arguably beyond the contractor’s reasonable control. For example, in the Miramar Water Litigation, filed in 2023 in Broward County, Florida, plaintiffs allege that improper water treatment practices by the City of Miramar and its consultants resulted in premature corrosion of residential plumbing systems. The case focuses on whether the corrosion control treatments implemented by the city and its consultants were sufficient to minimize the damage to copper piping before it dispensed the water to its residents.
Similarly, in 2024, in Malmquist v. City of Folsom, California (also called the Ladera Ranch Copper Pipe Class Action), the class action plaintiff alleges the City of Folsom failed to maintain proper corrosion control at its water treatment plant, causing the pH level of its water to rise and become corrosive, leading to pinhole leaks in copper piping. The court affirmed the denial of the plaintiff's motion for class certification, holding that the plaintiff had not shown that common issues predominated over individual ones. The court concluded that the existence, cause, and extent of damage to copper piping required individual proof.
Finally, a Hawaii lawsuit filed in 2021, Weisse v. LG Electronics, Inc., alleged that LG's Packaged Terminal Air Conditioners (PTACs) suffered from extensive corrosion due to atmospheric chloride levels and environmental conditions unique to Hawaii, rendering them unfit for the state.
Notably, water chemistry issues have also come up involving Aquatherm’s green polypropylene pipe. In a 2026 opinion, in King County, Washington v. Aquatherm GmbH, a Seattle jury awarded King County over $18 million in damages on a theory that Aquatherm’s revised (second) chemical recipe for its pipe lacked the primary antioxidants and metal deactivators necessary to prevent oxidation (rotting) in the pipes. Another large Aquatherm case was brought in 2021 in Oregon, United States v. Aquatherm GmbH, in which the government plaintiff alleges $40 million in damages to its 18-story office building, resulting from oxidative degradation (corrosion) of Aquatherm pipes. The government cited repeated failures of the pipes, alleged that the pipes were marketed to last for 50 years under "aggressive" water conditions, and that Aquatherm represented that the pipes could be used in systems that included copper components and chlorinated water.
Of course, the science involved in proving causation in these cases can get very complex. For example, in a 2021 case from Massachusetts, Nemirovsky v. Daikin N. Am., LLC, the court evaluated a jury verdict finding that the plaintiff’s expert provided sufficient proof to show that the evaporator coils in the air conditioning unit corroded prematurely not because they were themselves defective, but because the drain pan in the unit was made from Styrofoam rather than metal. The plaintiff’s expert’s theory was that corrosion of the coils was “accelerated by the inability of the electrons to get out through the ground on the bottom” because the pan was made of nonconductive Styrofoam rather than of a conductive metal material.
Synthesis
Contractors and design professionals are increasingly asked to manage risks that may be outside their direct control. That obligation can be frustrating because the alleged defect may trace back to municipal water chemistry, hidden component interactions inside equipment, or a manufacturer’s evolving formulation that is not apparent to outsiders at the time of design or installation. Even when the root cause lies upstream, downstream parties will likely face allegations of inadequate evaluation, selection, detailing, or installation. To mitigate these risks, the team should be asking:
- Do we understand the makeup of the materials and the environment in which they are to be installed?
- Does the data provided by the manufacturer appear complete?
- Do we have confidence in the manufacturer’s quality controls and consistency over time?
- Is there comparable material available from another manufacturer with stronger performance data or clearer installation guidance?
- What does it take to install these materials exactly as specified?
When these claims go into litigation, lawyers and their construction experts, like doctors, tend to “think horses, not zebras.” We typically look for the common symptoms, such as errors in the installation of pipe fittings, before considering more exotic causes such as formicary corrosion of copper pipes. As all potential causes of liability need to be considered, it is important to keep up with the emerging trends so that liability exposure can be evaluated holistically.
Attending the CLM Construction Conference is an excellent way to keep up with emerging product defect issues, as well as keeping up with trade magazines. In the end, staying current on these potential exposures will help practitioners spot the zebras on the horizon and do a better job keeping the lions at bay.
About the Author:
Jack Levy is a partner at GLB, PC. jack@theGLB.com