by Grant Lobdell


When a sprinkler does not perform as expected, it is easy to assume the issue is caused by a manufacturer defect.  However, listed sprinklers in the United States, as required by NFPA 13 (Section in the 2016 Edition), go through a wide variety of strict testing protocols at Underwriters Laboratory (UL) and/or Factory Mutual (FM) Approvals to greatly reduce this occurrence.  It is therefore generally far more likely that the sprinkler failure is due to something that occurred after the manufacturing process.

Sprinkler mishaps caused by physical contact (coat hanger resting on a sidewall sprinkler, forklift hitting a pendant sprinkler, etc.) can be easily explained.   However, when the mishap happens without this physical contact, it can be quite a mystery as to why.  Below is a list of the more common mysterious sprinkler mishaps with possible causes explained.

Issue: A sprinkler activated despite there being no fire.

Possible Cause: The sprinkler was stored in a high temperature environment.

Explanation: When a sprinkler is exposed to a temperature close to but not at its activation temperature, it can weaken the thermal element.  Solder release mechanism sprinklers in particular can experience what is called solder migration, which is caused when high storage temperatures soften the solder so it becomes slightly malleable but not enough to release.  When the storage temperature lowers and the sprinkler cools, the solder hardens in its new position (it has drifted) and is slightly weaker than it originally was, thus lowering the actual activation temperature.  Eventually, the sprinkler’s activation temperature is low enough where it will release in ambient conditions.  For this reason, NFPA 13 and NFPA 25 both outline maximum ceiling temperatures for various sprinkler types (Sections of the 2016 Edition and Section of the 2017 Edition, respectively).  This is also why NFPA 25 requires solder-type sprinklers with a temperature classification of extra high or greater that are exposed to continuous maximum allowable ambient temperature conditions to be tested every 5 years according to Section and A. of the 2017 Edition.  Be sure the sprinkler you have installed is the proper sprinkler for your environment and ensure any possible high temperature fluctuations are accounted for.  Care should also be taken when storing stock sprinklers in sprinkler cabinets or before installation.


Issue: A sprinkler is leaking water despite not being activated.

Possible Cause:  The water seal seat was disturbed due to overtightening during installation.

Explanation:  Sprinklers sold today in the United States should come with a technical datasheet on the product which will outline torque requirements.  If these requirements are not followed and the sprinkler is installed with excess force, the torque can distort the seat between the frame and the water seal.  Note that sometimes the leak can be very minor, only causing an excess of corrosion around the water seal specifically.  Should this occur, replacement of the sprinkler will be required according to the 2017 Edition of NFPA 25 Section


Issue: The frame of a sprinkler cracked and/or broke despite no one touching it.

Possible Cause: The water line behind the sprinkler froze.

Explanation: Generally, this occurs with glass bulb sprinklers.  To better understand how this occurs, you need to understand that the glass bulb is generally stronger (longitudinally) than the metal frame.  Therefore, when the water line freezes behind a sprinkler and pressure builds up, the first thing to break will not be the glass bulb.  Instead the sprinkler frame will give way and crack or sometimes separate completely.  If this occurs, freeze protection measures may need to be investigated.  The sprinkler should also be replaced according to the 2017 Edition of NFPA 25 Section


Issue: The fluid color in the glass bulb of a sprinkler faded.

Possible Cause:  The sprinkler was in a cold environment or in direct sunlight.

Explanation:  The fluid in a glass bulb sprinkler is generally an alcohol dyed to identify its classification.  This dye can lose its color from UV light, generally from the sun; but it has also been found in some cases to lose color due to cold temperatures (sometimes even regaining its color when the sprinkler is placed into a warm environment again).  It should be noted that the liquid inside a glass bulb can actually be the same across all classification.  The only differences are the dye and the size of an air bubble that is placed inside the tube.  The air bubble size is actually what gives rise to the varying activation temperatures and not the dye or liquid.  Therefore, the dye plays no part in performance and a sprinkler that has experienced fluid color change can still be left in service according to NFPA 25 (Section A. of the 2017 Edition).  In extreme cases of the dye fading where it appears clear, it can be hard to tell if the sprinkler has lost its fluid or if that fluid has just changed colors.  To determine this, you will want to identify if that air bubble is still present in the bulb (and roughly the same size as it was).  If it is present, the liquid is still there.  If not, the fluid has escaped and the sprinkler will need to be replaced according to the 2017 Edition of NFPA 25 Section


Issue: The fluid in the glass bulb of a sprinkler disappeared.

Possible Cause: The fluid leaked out of microscopic cracks in the glass caused by sprinkler mishandling during pre-installation.

Explanation:  While the glass bulb is quite strong longitudinally, it is quite fragile in many other ways.  The fluid inside can expand and put pressure on the glass to break it.  You can simply apply a latitudinal force to it as well.  Sometimes the glass can be weakened without fully or visibly breaking.  Microscopic cracks in the glass, which cannot be spotted with the naked eye, can occur in a glass bulb that has been mishandled prior to installation.  This can result from the sprinklers being dropped, for example (note that the manufacturer puts great care into sprinkler packaging to avoid this).  While the microscopic cracks aren’t enough to see a loss of fluid immediately, they can leak very slowly over time.  Sometimes you will notice coloration around the sprinkler that matches that of the fluid that is/was in the glass bulb.  Sprinklers that have experienced fluid loss need to be replaced according to the 2017 Edition of NFPA 25 Section as the activation temperature would be greatly affected.

All sprinkler manufacturers here in the United States also have technical service departments available to help.  Should you have further questions related these topics or issues not discussed here, please contact the manufacturer’s technical service department.  Dyne can also be reached at (800)632-2304 or


©Dyne Fire Protection Labs 2018