Mar 2000

Possible Sprinkler “O-Ring” Problems

Underwriters Laboratories Inc. (UL) is currently investigating field reports that certain Central Sprinkler Co. Model GB automatic sprinklers may leak or even worse, not operate during a fire because they require higher water pressure to operate than is usually available. The sprinklers in question contain “O-ring” water seals.

The Model GB series sprinkler heads were first introduced in 1988 and all in the series could be affected, regardless of the year of manufacture or installation. However, due to some recent design changes, not all of these models are equipped with “O-ring” water seals. Only those heads with the “O-ring” water seals are under investigation.

To date, initial testing of approximately 90 samples indicated 20% of these did not operate at a water pressure of 5 psi, which is the pressure sprinklers are required to operate at in order to earn a UL listing. Although the water pressure in most buildings exceeds this requirement, a few samples tested by UL did not operate at higher pressures (as high as 60 psi), which exceeds the water pressure available in many areas/buildings, including residences.

UL is also urging property owners whose buildings are provided with dry sprinklers that have “O-ring” water seals to have samples of those tested immediately. These heads may suffer the same problems as noted above. UL has received recent reports of incidents, in which dry sprinklers failed to operate in a fire, resulting in property damage. To date, UL has conducted operational tests on more than 300 samples taken from more than 40 different locations. The tests indicate that 49% of the samples required pressures higher than 7 psi to discharge water and 20% of the samples required pressures greater than 40 psi. These results, and input from community experts, led to a revision to the NFPA 25, Standard for the Inspection, Testing and Maintenance of Water-Based Fire Protection Systems. The revision became effective August 9, 1999 and effectively reduces the time interval for testing or replacement of these sprinklers from 50 yr. to 10 yr. after they have been in service. Recent test data indicates immediate testing of these heads is advisable.

All property owners should determine if Central Model GB or dry sprinklers with “O-rings” have been installed in their facilities. If so, a representative sample of these heads from each system should be removed and tested to determine if the heads are affected by this problem. Before removing the heads, it is recommended that you consult with the sprinkler manufacturers or their customer service representatives for information regarding removal and replacement of the test samples, as well as the applicable terms of the manufacturer’s warranty.

Once samples have been properly removed and packaged, they can be sent directly to Mr. Kerry Bell at Underwriters Laboratories, Inc., 333 Pfingsten Road, Northbrook, IL 60062 (Phone 847-272-8800 ext. 42629; e-mail: for the correct testing protocol. In keeping with UL’s not-for-profit, testing for public safety mission, UL will conduct these operational tests at no cost to the submitter during the course of the investigation, with the exception of expenses related to sprinkler removal, replacement, shipping and handling.