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Live event: return line leaks are secretly destroying your building

We recently held a live event to discuss how heating system return line leaks can lead to significant costs and energy efficiency losses in buildings. We covered a lot of ground, including how to detect leaks and what to do when you find one. Below is an overview of the key points and discussion topics brought up during the event.

The Costly Impact of Return Line Leaks

Return line leaks are a significant problem in terms of cost, primarily due to three factors:

  1. Continuous Water Replacement: Leaking water underground requires constant replacement with city water. This process of constantly refilling the system with cold water is costly - you're paying for more water, all the time.

  2. Energy Consumption: New water entering the system is typically colder (around 40 to 50 degrees Fahrenheit) and needs to be heated to around 200 degrees. This process consumes a significant amount of energy, leading to higher energy costs.

  3. Boiler Damage: The continuous addition of cold water to a hot boiler causes constant expansion and contraction of the boiler's metal due to rapid temperature changes and can lead to cracks and eventual failure. This damage represents a substantial cost in terms of repairs or replacement.

  4. Mineral Deposits: Adding fresh water frequently introduces more minerals into the system, requiring more frequent cleanings and potentially leading to additional boiler issues.

Detecting and Addressing the Issue

To detect return line leaks, focus on the water being added back into the system. Installing a meter on the makeup water feed can help monitor this. For instance, a building losing around 1000 gallons a day to leaks would be an example of a severe problem needing immediate attention.

When a leak is suspected, the initial step should be a visual inspection in areas like the boiler room or basement. In cases where the leak isn't visually apparent, an infrared gun can be used to detect hot spots underground, indicating a leak.

The very unfortunate thing about return line leaks is that they usually occur underground, out of sight. This is why it's important to have a sensor set up to record how much water is being added to the system.

Practical Steps to Manage Return Line Leaks

  1. Immediate Inspection: Conduct a thorough inspection of the boiler room and basement for visible signs of leaks.

  2. Infrared Detection: If no leaks are visible, use an infrared gun for thermal mapping to locate underground leaks.

  3. Plumber Intervention: Engage professional plumbers to address the identified leaks.

  4. Sensor Installation: Install sensors in strategic locations to continually monitor for potential leaks.

  5. Regular Maintenance: Perform routine checks and maintenance on the heating system to preemptively address issues.

Technology as a Key Ally

Modern technology, like the installation of specific sensors and control systems, plays a crucial role in identifying and managing heating system issues effectively. These systems can provide real-time data and alerts to building managers, enabling swift action to prevent costly damage and inefficiency.


Managing return line leaks and ensuring efficient heating systems require a blend of vigilance, technology, and proactive maintenance. By understanding the causes, effects, and solutions for these leaks, property managers can significantly reduce costs and extend the life of their heating systems. This approach not only saves money but also contributes to the overall well-being of the building's infrastructure and its occupants.