AFG Manufacturing explores how corrosion threatens fire sprinkler systems, why standard maintenance isn’t enough and what facility managers can do to prevent system failure
Corrosion poses a significant threat in fire sprinkler systems, often remaining undetected until it’s too late.
When corrosion compromises the integrity of these systems, it can lead to leaks that result in property damage and, more alarmingly, failure during a fire event, potentially resulting in loss of life.
Despite strict adherence to Inspection, Testing and Maintenance (ITM) protocols, corrosion continues to be a persistent challenge.
Traditional ITM protocols are essential for ensuring system reliability, but they can also inadvertently accelerate corrosion rates.
This occurs because maintenance activities often involve draining and refilling the system, which introduces fresh oxygen into the pipes, fueling the corrosion process.
Fortunately, advancements in corrosion prevention strategies and technologies have provided the fire protection industry with innovative ways to combat this issue.
By integrating modern corrosion monitoring and mitigation techniques, facility managers can enhance the longevity and effectiveness of fire sprinkler systems, ultimately improving life safety outcomes.
Understanding the corrosion triangle
Corrosion in fire sprinkler systems is the result of a chemical reaction that produces rust particles.
Unlike conventional plumbing systems where continuous water flow flushes away these particles, fire sprinkler systems are typically stagnant, allowing rust and debris to accumulate over time.
This buildup can lead to obstructions within the piping network, increasing the risk of reduced water flow or complete blockages.
In a fire emergency, such obstructions could prevent sprinkler heads from effectively discharging water, thereby exacerbating property damage and endangering lives.
The corrosion triangle consists of three essential elements: steel, water and oxygen.
When all three are present, corrosion is inevitable.
Fire sprinkler systems create an ideal environment for corrosion due to the continuous presence of these elements.
While wet systems remain filled with water and oxygen, dry systems are not immune to corrosion, as they still contain trapped moisture and oxygen.
Even small amounts of residual water in a dry system can trigger significant corrosion over time.
Strategies for mitigating corrosion risks
Eliminating any component of the corrosion triangle halts the corrosion process.
While completely removing steel, water, or oxygen is impractical, effective strategies exist to minimise their interaction, significantly reducing corrosion rates.
Venting trapped air in wet systems
One of the most effective methods to mitigate corrosion in wet pipe systems that utilise metallic piping, is venting trapped air.
Studies have demonstrated that removing trapped air increases the lifespan of pipes by reducing the amount of dissolved oxygen in the water.
To address this issue, the 2016 edition of NFPA 13 introduced a requirement for air vents in wet pipe systems constructed with metallic piping.
These vents release trapped air, preventing oxygen pockets from accelerating corrosion.
Draining condensation in dry systems
Dry pipe systems are designed to be free of water until activated, but condensation often forms within the pipes.
If not properly drained, this residual water can contribute to corrosion over time.
Ensuring that dry systems are installed with appropriate piping pitch and low-point drains is essential for preventing trapped water from stagnating within the system.
Corrosion inhibitors in dry systems
In addition to proper drainage, new technologies like “Vapor Pipe Shield” by General Air Products help combat corrosion in dry systems.
This system disperses a vapor-based corrosion inhibitor throughout the piping, creating a protective barrier between the steel and any residual moisture.
The role of inspection, testing and maintenance
Routine ITM schedules are designed to detect and address performance issues before they become critical.
However, wet systems are particularly susceptible to corrosion during maintenance activities.
Each time a wet system is drained and refilled, fresh oxygen is introduced into the water, accelerating the corrosion process.
Additionally, oxygen-rich air pockets often accumulate at high points in the system, further exacerbating the problem.
Recognising this, NFPA 13 has mandated the use of air vents in wet systems to mitigate corrosion risks.
One overlooked factor in corrosion prevention is the oxygen dissolved in the water itself.
During scheduled testing, fresh water, rich in oxygen, is introduced into the system.
To counteract this, recirculation systems such as those offered by AGF Manufacturing can be used to limit the introduction of new oxygen into the system.
Not only do these systems reduce corrosion, but they also conserve thousands of gallons of water annually, aligning with sustainability initiatives and reducing unnecessary waste.
Monitoring and preventing corrosion
Implementing corrosion monitoring is crucial for identifying potential risks before they escalate.
Various monitoring methods allow facility managers to track corrosion progression accurately, providing early warnings and enabling proactive maintenance.
Powered corrosion monitoring devices
These devices provide real-time data on corrosion rates, alerting personnel to significant changes within the system.
Corrosion coupons
Corrosion coupons involve placing a metal sample inside the system, which is later analysed to determine corrosion levels over time.
While not real-time, they offer valuable insights into long-term corrosion trends.
Passive corrosion monitors
Simple and cost-effective, these monitors indicate whether corrosion is occurring within the system, enabling early intervention.
By integrating these monitoring techniques, facility managers can gain a comprehensive understanding of the corrosion conditions within their fire sprinkler systems and implement corrective actions before severe damage occurs.
Why a remote inspector’s test valve is not a good air vent
Proper air venting is essential for reducing corrosion in wet pipe fire sprinkler systems.
NFPA 13 allows for multiple venting methods, including a manual valve, an automatic air vent, or a remote inspector’s test valve.
However, using an inspector’s test valve as an air vent is ineffective.
An inspector’s test valve is designed to simulate sprinkler activation and verify system functionality, not to provide continuous air removal.
Its typical placement is for testing purposes rather than at the system’s highest point, where air naturally accumulates.
Once water fills the vertical pipe leading to the drain, air can no longer escape, leaving pockets trapped in horizontal sections.
A dedicated air vent, such as an automatic or manual vent, is a better solution.
Automatic air vents continuously release trapped air, reducing maintenance needs and corrosion risks.
Manual vents require operation but provide controlled air release.
Properly placed remote inspector’s test valves could function as vents, but their accessibility for testing may be compromised.
NFPA 13 includes remote inspector’s test valves in its list of air venting methods, but their limitations make them unsuitable for effective air removal.
To prevent corrosion, maintain system integrity, and comply with NFPA 13, fire protection professionals should prioritize dedicated air venting solutions.
Installing the right venting strategy ensures system reliability and longevity while minimizing maintenance challenges.
Taking Action Against Corrosion
Effective corrosion management requires a proactive approach.
The integration of air vents, recirculation systems, corrosion inhibitors and monitoring devices significantly reduces corrosion risks and extends the lifespan of fire sprinkler systems.
Additionally, partnering with trusted manufacturers like AGF Manufacturing ensures access to high-quality corrosion prevention products tailored to the specific needs of fire protection systems in various environments.
From automatic air venting valves to innovative recirculation solutions, AGF offers a comprehensive range of products designed to enhance system longevity, reliability, and overall performance.
To safeguard lives and property, facility managers, fire protection engineers and building owners must remain vigilant against corrosion threats.
By implementing best practices in corrosion prevention and leveraging advanced technologies, they can ensure that fire sprinkler systems remain operational and effective when needed most.
For more information on corrosion prevention products or to find a distributor, please visit www.agfmfg.com
This article was originally published in the April 2025 issue of International Fire & Safety Journal – to read your FREE digital copy, click here.