Corrosion in sprinkler system piping can be a costly problem if leaks occur, causing damage to the interior of a structure, according to Matt Klaus, Principal Fire Protection Engineer with the National Fire Protection Association.
Replacing piping is no small expense, either. Corrosion can also cause blockages in the piping network, which can lead to an ineffective sprinkler system during a fire.
Corrosion can take on many forms, including oxidation, microbiologically influenced corrosion, and galvanic corrosion. The technical committees responsible for NFPA 13, Installation of Sprinkler Systems, have been looking at ways to eliminate or reduce corrosion in sprinkler systems for several revision cycles.
Reducing corrosion in dry systems can be achieved by eliminating all of the water from these systems after testing/activation and using alternative gases like nitrogen for charging these systems. For wet systems, limiting the amount of air in the system is the goal. Air trapped in pressurized sprinkler system piping results in an increase in the concentration of dissolved oxygen in the piping, enabling corrosion. Venting the trapped air in a wet system reduces this problem, so a revision to the wet system sprinkler system standard requires that a single air vent be installed for each system.
Depending upon the building geometry and sprinkler design, it is possible to trap air in many locations in the system, meaning a single vent may not be effective. Therefore, some stakeholders believe that the requirement adds cost to the property owner and the design team without any assurance that there is a long-term benefit to the system.