Whether a commercial or residential building, the benefits of a fire sprinkler system are huge! According to the National Fire Protection Association (NFPA), the civilian fire death rate for reported fires was 87% lower in properties with sprinklers than in properties with no automatic extinguishing system (AES).
Fire sprinkler systems are as unique as the dwelling in which they're installed. There are many types, interchangeable parts, and designs for any given fire sprinkler system. Unless you are a trained professional in the field, understanding the different systems and their uses can be confusing.
Don’t worry; we won’t leave you in suspense!
In this article, we’ll take a step back from looking at individual system components so we can gain a better understanding of systems as a whole. We’ll discuss the various types of sprinkler systems and their intended application. If you are looking for commercial or residential fire sprinkler system components, feel free to jump on over and check out our selection of commercial and residential fire sprinkler products.
If you’d like to learn more about fire sprinkler systems, keep reading.
Automatic Sprinkler System
An automatic sprinkler system activates when its thermal-sensitive element detects a temperature equal or greater than its specified temperature rating (generally 155°F) and discharges water over the area.
Aside from being considered one of the greatest painters of all time, did you know that Leonardo da Vinci also invented a fire sprinkler system very similar to today's fire sprinklers in the 15th century? Many do not know the long and rich history associated with sprinkler systems.
Leonardo da Vinci (credit)
In preparation for a large dinner party, da Vinci, who had interests ranging from art and literature to science and engineering (and everything in between), created some inventions to ensure the evening ran smoothly – one of which was a sprinkler system! This sprinkler system set the groundwork for the designs we still use today. Through a series of unfortunate events, many of the inventions he created to ensure dinner party ran smoothly did just the opposite. The conveyor belts he created moved too slow at first, but after some adjustments, they were too fast. The oven he created worked well, but the cooks burned the food so a small fire breaks out, which results in the activation of his sprinkler system. The sprinkler system worked as it should, but it left the food ruined, resulting in a failed dinner party and humiliation.
Though the first automatic sprinklers popped up in the early 1800s and Phillip H. Pratt received the first patent in 1872, Henry S. Parmalee is viewed as the inventor of the first practical automatic sprinklers. His designs, which improved upon those patented by Pratt, were patented in 1874.
Today, automatic sprinkler systems are a mandatory fixture in commercial buildings, schools, and many residential properties. There are four main types of sprinkler systems: wet pipe, dry pipe, preaction, and deluge sprinkler systems.
Wet Pipe Sprinkler System
Wet pipe sprinkler systems are the most common type of sprinkler system. The main reason is that they are the simplest to install, have the fewest system components, and are the most reliable given that water is always present in the system allowing them to activate quickly. They are called “wet pipe” because the pipes truly are filled with water at all times. Furthermore, as a direct result of their fewer system components, they are easier to maintain than the other automatic fire protection systems we will discuss.
Movies and tv shows misrepresent sprinkler systems (Credit)
Despite Hollywood's most fanciful misrepresentations, wet pipe sprinkler systems do not discharge all together when one unit activates (nor, for that matter, do they discharge when the fire alarm is pulled ... take that Lethal Weapon 4). That would be counterproductive and drain the water supply quickly. In all actuality, only the sprinklers closest to the fire will activate. The reason for this is that sprinkler heads only activate once the heat rises enough to meet their temperature rating (check out this article if you’d like to learn more about how fire sprinkler heads work).
Since wet pipe systems always have water within the pipes, they are not recommended for use in areas where they are at risk for exposure to freezing temperatures (think parking garage, unheated storage buildings, etc.).
Wet pipe fire sprinkler systems are available in three different configurations: with an alarm check valve, with maintained excess pressure, or with a straight pipe riser. The wet pipe sprinkler system with an alarm check valve uses an alarm check valve to prevent water from backflowing into the water supply, which means it can only move in one direction. A wet pipe sprinkler system with maintained extra pressure is meant to eliminate false alarms caused by pressure surges in the water supply by pumping excess pressure above the alarm check valve and suppressing the clapper. The most common configuration of a wet pipe system is a straight pipe riser, which uses a riser check valve and does not have an alarm port or retard chamber. (To learn more about risers click here).
Dry Pipe Sprinkler System
A dry pipe sprinkler system differs from a wet pipe system in that it contains compressed air within the pipes with pressure maintained by an electric air compressor, nitrogen bottles, or other air supply system. However, they are still considered an automatic sprinkler system.
Next time you're in a parking garage, look up! (Credit)
As mentioned above, parking garages and unheated storage buildings cannot use a wet pipe sprinkler system. Cue the dry pipe sprinkler system, which is perfect for these scenarios! According to the NFPA 13, this is the only time they are suitable for use. While a dry pipe system still uses water to suppress or extinguish a fire, it’s not consistently in the pipes, so it isn’t at risk for freezing.
The system can maintain its pressure through the use of supervisory pressure switches, which signal to the fire panel when there are changes in pressure. The panel can either release pressure through a ball valve or activates a pump to generate more pressure. During a fire emergency, the sprinkler head activates when the temperature meets its specified rating (note, the sprinklers themselves are often exactly the same as a wet system) and the pressure is released. As the pressure drops within the system, the air is replaced with water which is dispersed just like a wet system.
Key takeaway: a dry system keeps the pipes dry until there is a fire, eliminating the risk of freezing during cold temperature spells, but otherwise functions the same as a wet system once a sprinkler is activated.
Preaction Sprinkler System
A preaction sprinkler system operates similarly to the dry pipe and deluge systems. It uses closed sprinkler heads, has air in the pipes that may or may not be under pressure, and an electronically controlled valve holds the water back.
There are three types of preaction systems, according to NFPA 13 (18.104.22.168): single interlock, non-interlock, and double interlock. A single interlock system is one that allows water to pass into the piping when the detection devices operate. A non-interlock system allows water to pass when the detection devices or automatic sprinkler heads operate. Both the single interlock and the non-interlock systems activate after only one event. A double interlock system only admits water into the system when the automatic sprinkler heads and the detection devices operate, which means it activates slower than the other two types of preaction systems. There is no order to which the two events must occur to activate the double interlock system.
A computer room is an example a place you may find a preaction system (credit)
Preaction sprinkler systems best serve locations where avoiding unnecessary water exposure is of the utmost importance – computer labs, art galleries, etc. These systems are meant to guarantee operation only in an actual fire emergency.
Deluge Sprinkler System
Deluge sprinkler systems are similar to a wet pipe system in their operation, however, the sprinkler heads used within a deluge system are always open and do not operate independently. Similar to the preaction system, a valve holds the water back. However, in this system, there is an initiating device like a smoke detector that signals the panel to release water.
A foam system activates in an aircraft hanger (credit)
Since deluge sprinkler systems have an immediate reaction, they are best for use in highly flammable or hazardous areas like aircraft hangers, storage facilities for flammable liquids, power generating stations, etc. Because of the types of fire that can result in these locations, water is not always a sufficient choice to extinguish or suppress. In these instances, water can be mixed with foam to create a solution. The solution, which expands once it's released from the sprinkler heads, creates a protective blanket to smother the oxygen source and suppress or eliminate fire.
Why choose QRFS?
Feeling smarter? You should! Now that you’re an expert in the four types of sprinkler systems, ready for your own fire protection system? Let us help you start building the best system to meet the needs of your facility.
At QRFS we stock fire sprinkler system components for Residential and Commercial wet and dry systems (we have access to, but do not stock, deluge and preaction systems at present). For wet systems, we offer commercial and residential risers in a variety of configurations, sprinkler heads, sprinkler accessories, standpipe systems (an entirely different topic), gauges, testing and monitoring solutions, and installation tools to meet your sprinkler system specifications.
We have a great line of Residential Risers with Basic Trim, Basic Trim with Test and Drain, and Basic Trim with Pressure Relief Kit. All three configurations have a working pressure of 175 PSI and parts are UL listed. Also, we offer Commercial Risers with your choice of a Test and Drain or ball valve.
We carry four brands of fire sprinkler heads from Tyco, Reliable, Victaulic, and Senju. All of our brands are available in a variety of temperatures, finishes, and sizes.
In addition, at QRFS we take the time to educate ourselves in NFPA Code and industry best practices so we can help you find the right product at the right time. At QRFS you get the best of both worlds: the selection of a traditional distributor with the cost-advantages and ease-of-use of an eCommerce marketplace. What are you waiting for? Don’t delay and start your project today with QRFS.com!
Still have questions? Comment below and we’ll reply as quickly as possible to get your project on the right track.
This blog was originally posted by Jason Hugo and Anna Hartenbach at QRFS.com/blog on September 21, 2017. If you found this article useful, check us out at Facebook.com/QuickResponseFireSupply or on Twitter @QuickResponseFS.