Limit the chances of a fire sprinkler leak

If a fire sprinkler has discharged water in the absence of a fire, an investigation should be undertaken to determine why the sprinkler operated.
By Staff March 1, 2001

If a fire sprinkler has discharged water in the absence of a fire, an investigation should be undertaken to determine why the sprinkler operated.

According to the National Fire Sprinkler Association (Wisconsin Chapter), the reasons typically are inadvertent overheating, freezing, mechanical damage, corrosion, or deliberate sabotage.

Overheating —Automatic sprinklers respond to heat, and cannot differentiate between “good heat” and “bad heat.” If sprinklers are located close to unit heaters, under skylights and in other areas exposed to high heat, the applicable rules of NFPA Standard 13 Installation of Sprinkler Systems require that higher temperature rated sprinklers be used. This means that the solder elements or glass bulbs used as the operating mechanisms will be designed to activate at temperatures of 200%%MDASSML%%300 F (93%%MDASSML%%149 C) instead of the normal 155%%MDASSML%%165 F (68%%MDASSML%%74 C). If new sources of heat are added, a qualified contractor should be hired to make the necessary modifications. Temporary heat-producing sources such as construction lighting and television cameras have also been known to activate sprinklers.

Freezing —Most sprinkler systems are wet pipe systems, meaning that the piping is filled with water. If a system — or even a small portion of a system — is exposed to freezing temperatures, water in the piping can turn to ice, expanding in volume and producing thousands of pounds of pressure. Such pressures can break fittings, as well as force open the valve caps of sprinklers, resulting in apparent accidental discharge or leakage when the system thaws. A common cause of exposure of sprinkler pipe to freezing temperatures is the movement or removal of pipe installation and the subsequent failure to replace it.

Mechanical damage — Although it’s obvious that a large force can immediately open a sprinkler, it is less obvious that a smaller impact can do the same thing over time. That’s why it is important that sprinklers be carefully handled during the installation process, and that the proper wrenches be used during their installation. Special wrenches are often required by the manufacturers’ literature to reduce the possibility of slippage that can damage the sprinkler operating mechanism, potentially resulting in a release of parts weeks or months later. Building renovations can also result in impacts of sprinklers, leading to an inadvertent discharge or leakage at a later date.

Corrosion — Corrosion can result in a weakening of parts, and a subsequent release of water. This situation can occur among very old sprinklers, or sooner with sprinklers installed in a harsh environment. Many fire codes require enforcement of NFPA 25Standard for the Inspection, Testing, and Maintenance of Water-Based Fire Protection Systems . This standard requires that the building owner replace sprinklers that exhibit corrosion, loading, or other damage.

Deliberate sabotage — Deliberate acts of sabotage must also be considered when investigating the reasons for sprinkler discharge. Vandalism and insurance fraud have been found in the past to be motivations for tampering with sprinklers.

Manufacturing defect — Although very rare, the possibility of a manufacturing defect can be considered when all other potential reasons for inadvertent operation have been ruled out. This case could take the form of a problem in loading or tolerances on the parts. The sprinkler manufacturer should be contacted, and arrangements can be made for professional analysis.

The NFSA is a trade association comprised of installers and manufacturers of fire sprinklers and related equipment and services. Visit their web site at .