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Safeguarding Hydronic HVAC Systems: An Overview of Backflow Prevention

Backflow prevention is a crucial element in any Hydronic HVAC system — a silent guardian that protects the integrity of commercial plumbing. Let's delve into backflow prevention and its pivotal role in maintaining the efficiency and safety of hydronic HVAC setups.

The Basics of Backflow

The first major recorded backflow incident occurred in the summer of 1933, during the Chicago World's Fair. Two major hotels shared a common water supply and unbeknownst to the bustling hoard of victors, dangerous cross-connections in the hotel plumbing systems allowed amoebic dysentery to spread — around 200 people fell severely ill and 98 lost their lives that summer. This tragedy serves as a reminder of the paramount importance of backflow prevention!

Backflow can occur in two primary ways: backpressure and backsiphonage.

Backpressure arises when downstream water pressure in a non-potable system surpasses the pressure of water distribution lines containing potable water. Backsiphonage occurs when the normal flow is reversed due to negative or sub-atmospheric pressure in a piping system, like reversing natural flow by creating a vacuum when drinking through a straw.

Common causes of backpressure and backsiphonage include water supply interruptions during water-line flushing, firefighting events, water-main breaks, installation of heating systems, and the installation or repair of pressure-producing or -altering systems.

One specific concern related to backflow prevention in HVAC systems is the connection to fire protection systems. Fire protection systems frequently employ uncoated black iron pipes, which are not considered suitable for water system piping material by plumbing officials. This connection introduces the risk of contamination of safe drinking water.

Types of Backflow Preventers

Backflow preventers come in two categories: testable and non-testable.

Testable backflow preventers are used in more hazardous cross-connection applications and require annual testing to ensure they function correctly. These preventers may require cleaning, rebuilding, or replacement if issues are detected during testing.

Non-testable backflow preventers are suitable for less hazardous cross-connection applications, and they typically function until the fixture they serve is in use or until they visibly fail. Periodic replacement may be required for some non-testable devices to maintain safety standards.

Selecting a Backflow Preventer

A technical sales consultant from Hoffman Hydronics can help you determine the right kind of backflow preventer for your HVAC system — such as check valves from Metraflex, Taco Comfort Solutions or Titan Flow Control — but there are a few key things to keep in mind when looking for the right preventer.

1. Flow Performance

Review the pressure/flow curves provided by the manufacturer of the backflow preventer, and ensure they align with your specific application needs. The flow characteristics of the preventer directly impact the overall flow performance in the building's potable water or fire sprinkler system. Ensure that the selected preventer is sized correctly to meet the flow requirements. Because oversizing or undersizing the device can lead to premature wear and tear.

2. Serviceability

Backflow preventers, like all Hydronic HVAC equipment, will require maintenance and servicing over time. When selecting a backflow preventer, consider factors like the types of tools needed for servicing, ease of access to internal components, availability of replacement parts, and the complexity of moving parts. The ability to service the valve efficiently can significantly impact its lifetime cost and the convenience of plumbers tasked with maintenance.

3. Code Compliance

Local plumbing codes and regulations play a critical role in the selection of the right backflow preventer. Different applications may have varying code requirements, such as whether a device is considered a health hazard, the need for testable or non-testable devices, or the specific type of backflow preventer required. It's essential to stay informed about these local codes and regulations and consult with local authorities to ensure your backflow preventer meets compliance standards.

Working with a Hoffman Hydronics technical sales consultant can help you ensure your hydronic HVAC designs meet or exceed backflow prevention standards. Our sales team remains up to date on local and national plumbing codes to provide customers with the best possible service!

Regular Maintenance

Like any other component in a hydronic HVAC system, backflow preventers require regular inspection and maintenance. Be sure to follow manufacturer recommendations for inspection and maintenance. Your technical sales consultant from Hoffman Hydronics may be able to recommend a local contractor to assist you with developing a comprehensive maintenance schedule, including testing and servicing backflow preventers to guarantee their continued effectiveness.


In the realm of hydronic HVAC, backflow prevention is not merely a checkbox on a design checklist; it's a fundamental aspect that safeguards public health and the integrity of your system. Proper backflow prevention measures help mitigate risks and ensure the health and well-being of building occupants and the longevity of your Hydronic HVAC system.

By understanding the nuances of backflow prevention, your Hoffman Hydronics technical sales consultant can help you create an HVAC system that not only excels in efficiency but also upholds standards of safety and reliability. Reach out today if you are interested in learning more about backflow prevention for your commercial hydronic HVAC system!

Sales & Training Coordinator KayLyn Alexander contributed to this post.

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