Sprinkler systems can malfunction when temperatures drop. When any portion of a sprinkler system is exposed to freezing temperatures, water in the piping can turn to ice, expand in volume, and produce thousands of pounds of pressure. The pressure can force sprinklers to operate and break fittings. As a result, water leaks or is discharged from the system when the ice thaws. Normally sprinkler system failures, due to freezing, aren’t discovered until after the water starts to cause damage because it is discharging.
After a water discharge from a sprinkler system, building owners face property damage, business interruption, and irate tenants and customers. Most fire sprinkler contractors have the ability to eliminate the chances of a freeze failure with proper installation, but to make sure it never happens, building owners also need to be involved.
Most sprinkler systems are wet pipe systems, meaning that the piping is normally filled with water. A wet system freeze failure has two primary causes:
Installation standards define how and where wet piping systems are supposed to be installed, but part of the responsibility rests with building owners and operators. According to NFPA 25, paragraph 188.8.131.52, Standard for the Inspection, Testing, and Maintenance of Water-Based Fire Protection Systems:
“The building owner shall ensure that all areas of the building containing water-filled piping shall be maintained at a minimum temperature of 40°F (4.4°C) and not exposed to freezing conditions.”
A wet system freeze failure can occur in an area where a building used to be heated, but is now left cold or where a piece of insulation is disrupted, leaving piping exposed. In either scenario, the building owner has the ability to prevent the freeze failure with regular maintenance and inspection.
Dry sprinkler systems can also have failures due to freezing in cold conditions. A dry pipe sprinkler system is a specialized type of fire sprinkler system that is typically installed in areas of a building that is exposed to freezing temperatures. The pipes are normally dry and charged with compressed air. The compressed air holds the dry valve closed and prevents water from entering the system. When a sprinkler activates, the compressed air leaks out, the valve opens, and the system piping is filled with water. If the dry system is properly installed, the water will drain, but that doesn’t always happen.
In addition, if a dry system’s pipes are not sloped back towards the source or an auxiliary drain, the water will pool within the piping. When winter comes around, the uninsulated piping freezes, creating problems just like a wet system freeze failure. In buildings where there is a low quality of construction, this is a common scenario. Residential buildings, where construction is fast and lacks proper oversight, are particularly prone to dry system freeze failures.
Ideally, all sprinkler systems would be properly designed and installed for their environment. Dry sprinkler systems would properly slope in order to drain and wet systems would be properly insulated in areas that drop below 40°F. Unfortunately, the ideal situation isn’t always a reality and you can’t just turn off a fire protection system every time it gets cold to prevent potential freezing problems.
Every year, we find dry pipe systems that are improperly installed and do not drain as a result. Building owners don’t have much control over the slope of their dry pipe systems, but they can make sure the systems are otherwise properly drained before freezing weather arrives. In a wet system, building owners and operators can ensure the pipes remain heated and insulated enough to not freeze.
To prevent a pipe freezing scenario, building owners and operators should take preparations before cold weather, routine actions during cold weather, and special precautions when a building might be unattended for an extended period of time.
County Fire Protection strongly recommends that all work on fire sprinkler systems be performed by trained, experienced individuals who are employed by a professional fire protection company.
Freezing of water-based fire protection systems is avoidable. Many sprinkler freeze failures occur due to inadequate building heat. Building owners who actively monitor and maintain building heat will help to reduce many fire system freeze failure impairments.
In cold building spaces where wet sprinkler systems are located, like above the ceiling, you can install thermometers that can be checked remotely. If a wet system freezing is a major concern, you should consider replacing it with a dry system. A dry system is less likely to freeze, but they still require monitoring and maintenance.
During extended periods of cold weather or vacancy, building owners should safely increase heat in all building spaces and turn off energy savings settings. Extended idle periods occur when building occupants leave for a long weekend or holiday. During these periods, building owners need to make sure suitable means of heat loss detection are maintained. Where building temperatures are detected at or below 40°F, prompt action by the building owner is needed. Every sprinkler system has a control valve. Building operators should know where the sprinkler valves are in order to turn them off in the event of a system failure.