When Water Treatment Goes Wrong: A Commercial HVAC Investigation
In commercial buildings, HVAC systems are often complex networks of boilers, valves, and chemical treatment systems that have to work in perfect balance. When even one small component fails, the effects can ripple throughout an entire facility.
I was called to investigate an incident at a hospital where a heating failure caused freezing and water damage during the middle of winter. What began as a question about a boiler shutdown turned out to be a chemical compatibility problem hidden deep within the system.
The Case: Steam Boilers That Suddenly Stopped Working
The hospital’s HVAC system relied on several steam boilers to generate heat for the building by supplying steam to several steam coils that are intended to preheat outdoor air entering the building’s air ducts. The boilers operated as expected—until they didn’t. During a period of freezing weather, the boilers shut down unexpectedly, causing steam in the steam coils to condense back to water. Cold outdoor air was then allowed to flow into the system without being preheated. That allowed the condensed water in the steam coils to freeze, expand, and rupture, leading to leaks and property damage.
When I arrived, the question was simple: Why did the boilers stop running?
The Investigation: Following the Water Supply
Steam boilers require carefully treated water to prevent corrosion and scaling. The incoming water is processed with chemical additives before passing through a solenoid valve and into the boilers.
During my inspection, I noticed damage to the solenoid valve assembly. The valve was supposed to regulate treated water entering the system, but the valve showed signs of corrosion and deterioration. Upon closer examination, the corroded valve body showed evidence of water leaking out of the valve bonnet, indicating that an EPDM rubber O-ring in the valve had degraded far more than normal wear would suggest.
After reviewing the chemical treatment records, it became clear that the water treatment chemicals used at the facility were incompatible with the solenoid valve’s materials. The chemical reaction had slowly eaten away at the O-ring and corroded the valve body.
The Findings: A Chain Reaction of Failures
The corrosion prevented the valve from actuating, restricting water flow through the solenoid valve and blocking supply to the boilers. When the boilers sensed low water levels, their safety controls automatically shut them down to prevent overheating. With no steam available to preheat incoming air, frigid outside air entered the system, freezing the coils and causing damage throughout the hospital.
Understanding the Bigger Picture
This case was a reminder that not every mechanical failure comes from a worn-out part or a faulty installation. In complex systems like hospitals, even the smallest mismatch in materials or chemistry can undermine reliability.
What failed wasn’t a piece of equipment—it was an assumption. The chemicals used to protect the boilers interacted with the valve materials in ways no one expected, setting off a quiet chain reaction that only became visible after the damage was done.
That’s what makes forensic engineering so valuable. Every component, every connection, every chemical has a role—and understanding how they interact is what keeps critical facilities safe and operational.
About the Author
John M. Rophael, P.E., is a mechanical consulting engineer at EDT Forensic Engineering and Consulting. He applies more than a decade of experience to evaluate the root cause of mechanical and piping system failures and to provide consultation related to HVAC systems, plumbing, mechanical design, damage assessment, and code interpretation.