How Do Fire Sprinklers Work?

Posted July 13, 2020 by Koorsen Fire & Security

Checking Sprinkler Valve

Everyone is familiar with them – the automatic sprinklers protruding through ceilings that offer protection in the event of a fire.

But while most are aware of them, many have a lot of confusion and misconceptions about how these fire-fighting systems actually work.

Fire Sprinkler Misconceptions

First, it may be helpful to dispel some common and potentially harmful misconceptions many people have about fire sprinklers and how they work.

Here are just a few misconceptions:

  • Smoke triggers a fire sprinkler
  • Once one automatic sprinkler activates, all automatic sprinklers in the system activate together
  • Fire sprinkler activation automatically means massive water damage
  • Smoke detectors activate fire sprinklers
  • Fire sprinklers will shut off automatically once a fire is under control

Continue reading to learn how fire sprinklers actually work so that you and your property can be better prepared in the event of a fire.

Basic Parts of a Fire Sprinkler System

To better understand how the system works as a whole, it is helpful to know the various parts that make up a fire sprinkler system:

  • Automatic Sprinklers: The part of the fire sprinkler system you see throughout the building which disperses the water onto the fire. There is a wide variety of automatic sprinkler types that suit varying needs and settings.

  • Heat-Sensitive Element: A component of each automatic sprinkler, the heat-sensitive element, is the all-important trigger that activates the sprinkler. The most common type of heat-sensitive element is a glass bulb filled with a kind of glycerin-based liquid which expands and bursts in response to fire-related temperatures, typically between 135-165 degrees Fahrenheit.

  • Sprinkler System Cross and Main Pipes: The pipes that run above the ceilings and behind the walls which carry and hold the pressurized water that will be dispersed through the automatic sprinkler(s) in the event of a fire.

  • Sprinkler System Risers: The pipes that connect the sprinkler system cross and main pipes to the domestic water supply for the building.

  • Fire Sprinkler Pressure Gauges: Gauges that measure the water pressure within the sprinkler system to indicate whether or not sufficient pressure is present to efficiently send water through the system in the event of a fire.

  • System Control Valves: Valves used to drain, test, and isolate specific sections of the fire sprinkler system.

  • Water Flow Switch: A switch that is activated when water runs through the sprinkler system that sends an alarm to alert local authorities that the system has been triggered.

  • Water Motor Gong: A device that sounds an alarm when water is actively flowing through the sprinkler system.

  • Main Drains: Where the system’s water can be drained and removed in the event of maintenance or testing.

Now that the main elements of the sprinkler system have been defined, it will be easier to understand how the parts work together to make the whole system work.

How are Fire Sprinklers Activated?

As may now be clear from the above, automatic sprinklers are heat activated, not smoke activated, and they only activate one automatic sprinkler at a time in most systems.

In most wet and dry pipe systems, an automatic sprinkler is activated when the heat reaches fire-related temperatures, usually within the range of 135-165 degrees Fahrenheit, depending on the system.

Only the automatic sprinkler experiencing those temperatures will then be activated, which occurs when the heat-sensitive glass bulb breaks in response to the heat.

Once the bulb breaks, the sprinkler system’s water will be released through the automatic sprinkler and will flow down and out over the fire, suppressing the fire and preventing it from spreading and re-igniting. Because most fire sprinklers only activate at the automatic sprinklers where the fire is, a fire can often be stopped and kept to the first room/area it began without other automatic sprinklers needing to activate.

Where is the Water Stored?

There is some variance among fire sprinkler systems as to where the water is stored and how it gets to the sprinkler head upon activation.

  • Wet Pipe Fire Sprinklers: In a wet pipe system, the pipes are filled with water that is slightly pressurized. When the system is activated, the water then releases immediately through the activated automated sprinkler. Wet pipe systems have the fastest response time and are the easiest to install, but may not be ideal for regions where pipes may freeze or where a leak could be devastating.

  • Dry Pipe Fire Sprinklers: In a dry pipe system, pressurized air fills the pipes behind the automatic sprinklers while the water is kept back behind a valve. When an automatic sprinkler is activated, the valve is lifted and water is released to flow through the system to the activated automatic sprinkler.

All sprinkler systems, wet or dry, are connected to a domestic water supply through the system’s risers, which are usually located in a designated riser room along with the system’s gauges and controls.

How are Fire Sprinklers Turned Off?

Many may assume that a fire sprinkler will automatically switch to off after a fire is extinguished or under control. This is certainly not the case.

Whether it is after a fire is extinguished, or when an automatic sprinkler malfunctions or a pipe breaks, the system will have to be manually shut off so that water flow is halted and the activated or malfunctioning automatic sprinkler can be repaired/replaced before the system is reset.

This is why it is good to know where the system’s risers are. On the main risers – the pipes connecting the fire sprinkler system to the water supply – there will be water control valves that allow you to turn the water flow off and on.

In the event of an actual fire, it will likely be emergency responders who take care of this step. But, in the event of a malfunctioning or damaged automatic sprinkler or pipe, it may be pertinent to know where the control valve is so that you can shut off the water and prevent needless water damage.

Ensure Proper Maintenance and Testing

According to NFPA 25, fire sprinkler systems must undergo regular inspections and tests to ensure they are functioning properly.

System gauges are to be inspected weekly or monthly, alarm devices and control valves should be inspected quarterly, and pipes, fittings, and bracings annually. The system should receive internal inspections every five years.

Mechanical elements of the system are to be tested quarterly, and switches every six months. The whole system should undergo testing and tagging annually.

While facility owners or staff members can do some of the basic inspections, testing and full inspections need to be carried out by professionals to ensure a truly functioning system that will effectively protect life and property.

Koorsen Fire & Security has been industry-leading experts in the fire protection industry for over 70 years. Whether your system needs repair, or you need help with regular maintenance and testing routines to ensure you stay up to code, the Koorsen team is ready to serve you.

Call Koorsen today with your questions or to schedule a visit.

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Topics: Fire Sprinkler Systems, Fire Safety & Security

Disclaimer: The information in this article is for informational purposes only. It is believed to be reliable, but Koorsen Fire & Security assumes no responsibility or liability for any errors or omissions in the content of this article. It does not constitute professional advice. The user of this article or the product(s) is responsible for verifying the information's accuracy from all available sources, including the product manufacturer. The authority having jurisdiction should be contacted for code interpretations.