Wet systems are characterized by a pipe network constantly maintained with pressurized water. Water is held back by a closed/un-activated sprinkler.
Dry systems are categorized by a pressurized pipe network void of water. When pressurized gas is released from the system piping (i.e. in a fire event), the differential-pressure valve opens and fills the piping with water.
A backflow prevention device must be installed between the water source and the fire sprinkler system. A backflow preventer provides two main functions.
Control valves can be found in multiple locations on a fire sprinkler system. All control valves are required to be an ‘indicating’ type, meaning that they must provide a visual indication as to the opened or closed status of the valve.
Common types of indicating valves include:
A main drain allows for the removal of water from the system and is a means of providing a forward flow test of the water supply. The main drain must be sized according to the size of the riser.
An auxiliary drain must be provided in any situation where the pipe network changes directions and traps water in excess of five gallons.
With few exceptions every fire sprinkler system is required to have a fire department connection. Commonly referred to as the FDC, the fire department connection allows responding fire personnel to pump additional water into the fire sprinkler system, both supplementing the existing water supply to the sprinklers and/or supporting firefighters entering the building.
Each sprinkler system zone must be equipped with a waterflow detection device that will signal when there is a waterflow event. In a wet system, waterflow is detected and signaled by an alarm check valve used in conjunction with a water motor gong, or by a paddle style flow switch that is monitored by the fire alarm system.
The fire protection industry now requires a means of venting trapped air from a wet system pipe network as it is filled with water. The 2016 edition of NFPA 13: Standard for the Installation of Sprinkler Systems added Section 7.1.5 which requires a single air vent to be installed on each wet pipe system using metallic pipe.
By ejecting trapped air from the pipe network as it is filled with water, the air vent accomplishes two important functions.
Despite all the updates to sprinkler system technology and industry regulations, the fact remains: all fire sprinkler systems eventually corrode to a point of no return.
Many building owners overlook this unfortunate truth until leaks begin to develop in their facilities. What’s more, most building owners are rarely proactive in maintaining a corroding fire sprinkler system until damaging leaks have begun to develop.
Fire sprinkler systems require routine inspection, testing, and maintenance. The frequency of some of these inspection, testing, and maintenance items range from monthly, quarterly, semiannually, annually, or even as seldom as every several years. Requirements differ from dry and preaction to wet and deluge sprinkler systems but generally include inspecting and testing valves, piping, gauges, fittings, and other components of the sprinkler system.
A unique requirement for dry and preaction systems is that they are required to have a full system trip every three years to ensure water can effectively flow throughout the system, and a full internal obstruction investigation every five years. A unique requirement for wet and deluge systems is that they need to be drained and internally inspected every five years for corrosion and blockages. Details about these inspection, testing, and maintenance requirements can be found in the edition of NFPA 25 Handbook your state or local municipality is using.
The purpose of performing routine maintenance is simple - to ensure that the fire sprinkler system will perform as designed if the event of a fire. Per a 2017 report by NFPA, it was found that only 96% of systems were effective, meaning 1 out of every 25 systems did not put out a fire when they were activated. Of the system failures, 81% failed because they were unable to deliver water to the fire. This failure can be caused by closed valves, corrosion, or blockages within the sprinkler system. Performing routine inspecting, testing, and maintenance is essential to preventing these sprinkler system failures.
While these inspection, testing, and maintenance items are a necessary component of having a fire sprinkler system, we need to mindful of the impact this has on system corrosion over time. With dry and preaction systems, every time the system experiences a full system trip fresh water is being introduced to the system. After the trip is completed and the system is drained, pools of trapped water will remain in the system providing an opportunity for oxygen to dissolve into the water and corrode and form rust within the steel pipe.
In comparison, with wet and deluge systems every time the system is drained to for an internal investigation oxygen gets reintroduced to the system via the main drain. This oxygen becomes trapped in the system after the inspection and dissolves into the system’s water and corrodes the steel pipe where the trapped air collects, most often at the high points of the wet system. Without taking precautions, overtime these activities will damage the sprinkler system and eventually cause leaks and other issues that we are attempting to prevent with these inspections in the first place.
ECS offers several solutions that allow you to perform routine maintenance and testing while preventing future damage to your sprinkler system. With dry and preaction systems, a nitrogen generator will eliminate oxygen from your system replacing it with inert nitrogen gas, thus preventing future corrosion in the system. With wet and deluge systems, ECS offers automatic air vents that allow trapped oxygen to escape from the system before it can corrode the steel pipe. Using any of ECS’ corrosion mitigation products allows for proper system testing and maintenance without the adverse effects of re-introducing oxygen and/or water to the fire protection system.
Unfortunately, traditional leak repair is an example of a positive feedback loop, in which one variable in the system contributes to the exacerbation of another variable. This leads to net instability in the system.
In the case of fire sprinkler systems, each leak repair contributes to additional corrosion activity in the system. After enough corrosion damage has occurred in the pipe network, new oxygen introduced from a single leak repair can be enough to cause the next leak. Theoretically, this would cause a never-ending cycle of leak and subsequent leak repair. When we review the history of fire sprinkler systems we work on, we very commonly find an increase in leak frequency over time.
Even so, once the first several leaks show up in their sprinkler systems, most building owners opt for simple, cheap repairs. But once the leaks have become too common or too expensive, the owner typically defers to the expertise of their fire sprinkler contractor for a solution — and, more often than not, the contractor recommends a complete system replacement.
However, a complete system replacement does not take into consideration the highly localized nature of corrosion, and usually leads to a very expensive project to replace the pipe — much of which may still be in excellent condition.
So, when it comes to repairing vs. replacing the fire sprinkler system, surgical pipe replacement is the clear solution. Here’s a more detailed look at how system repair costs are calculated:
All fire sprinkler systems corrode, though the severity of corrosion and the need for a corrosion maintenance protocol depends on a large variety of factors. Consider your unique system layout, the frequency of maintenance, system materials (i.e. black steel or galvanized pipe), as well as pipe schedule. What you need to do and how soon heavily depends on your facility’s tolerance for leaks. Will down time for repairs impact your business? Will a leak affect business continuity? Will obstructions and a failure to operate in the event of a fire cause greater life safety risks? Can you afford not to consider corrosion management for your facility?
For some systems a simple vent installation can greatly reduce corrosion and extend the service life of the system. For mission critical or cold storage applications, you may need a nitrogen inerting protocol to arrest corrosion and protect the system. Being proactive can greatly reduce risk.
Call us at (314) 432-1377 or use the form below to schedule a time to talk to an ECS engineer about your system’s specific needs.
