Understanding Preaction Systems — Which Type Fits Your Facility?
When it comes to protecting valuable spaces like data centers, museums, and control rooms, not every fire protection system is created equal. Some spaces simply can’t risk an accidental discharge or the downtime that follows. That’s where preaction systems shine, offering precise control over when water enters the system and how it’s released.
In our recent Expert Chat with Alan Larson, CET, CFPS from Reliable Automatic Sprinkler Co., we took a closer look at the types of preaction systems and how they’re used to protect mission-critical environments. Here’s a quick breakdown to help you decide which system might fit your facility best.
Want to watch the full discussion? View the Expert Chat on-demand for a deeper dive into system selection and cabinet-mounted designs.
What Makes a Preaction System Different
Unlike traditional wet-pipe systems which keep water in the piping at all times, preaction systems stay dry until a fire is detected. That’s a big deal in spaces filled with expensive equipment, sensitive electronics, or irreplaceable items.A preaction system uses detection and control to decide when water enters the piping network. Depending on the design, that decision can rely on one or two “triggers” — detection, loss of air pressure, or both.
Single-Interlock Preaction Systems
How it works:
A single-interlock system requires just one event — typically heat or smoke detection — to open the valve and fill the pipes with water. Sprinkler heads remain closed until heat from a fire activates them, and only then is water released. This allows time for human intervention before water is released.Best for:
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- Data centers
- Archives
- Libraries or museums
- Any space where false discharge could cause significant damage or downtime
Why it’s popular:
It gives early warning and fast activation without the risk of accidental water release. If detection goes off but no sprinklers open, you can reset the system before any damage occurs.
If uptime is critical and you can’t risk water in the pipes unless there’s a verified fire, this is the system to start your conversation with.
Double-Interlock Preaction Systems
How it works:
Double-interlock systems require two events to occur before releasing water:
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- Activation of detection (heat or smoke), and
- Loss of air or nitrogen pressure due to an open sprinkler head.
Best for:
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- Freezer or cold storage rooms
- Environments with mission-critical or high value assets where introducing water could cause electrical or operational shutdowns
Key takeaway:
This design is very common for data centers, server rooms and other electrical fire hazards because it adds an extra layer of protection against unwanted discharge. However, it does mean a slight delay in water delivery. As Alan put it, “You’re trading speed for certainty.” But, that certainty may allow data center facility managers a better night’s sleep.
Non-Interlock Preaction Systems
How it works:
Non-interlock systems activate when either detection or loss of pressure occurs. They’re less common because they offer fewer safeguards against false trips.
Best for:
Special applications where the owner or AHJ specifically calls for it. Most facilities won’t use this setup due to its higher risk of accidental activation (i.e. water quickly enters the sprinkler pipe network).
If your team is weighing non-interlock options, make sure to involve both your fire protection contractor and AHJ early in the design phase — they can help evaluate if it’s truly necessary.
Low-Pressure Dry Pipe Systems — The Quiet Workhorse
Not every special system uses a preaction valve. Some facilities rely on low-pressure dry pipe systems, which have earned a reputation as the reliable, low-maintenance alternative.
Why they matter:
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- They use less compressed air or nitrogen, which means smaller compressors or generators.
- They activate faster because there’s less air to clear before water reaches the sprinklers.
- They’re less prone to leaks and false trips.
- They often cost less to maintain over time.
In large-scale facilities like data centers, where airflow, noise, and maintenance budgets are all factors, low-pressure dry systems can provide a balance between performance and practicality.
Curious how low-pressure dry systems compare to preaction in your setup? Schedule a 10-minute chat — we can help you weigh the options for your facility.
Choosing the Right Preaction System for Your Facility
Selecting the right fire protection system comes down to one key thing: risk tolerance.
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- How sensitive is your equipment to water?
- How much downtime can your operation handle?
- What do local codes and insurance providers require?
For data centers and other mission-critical spaces, the right answer usually involves a preaction system — or in some cases, a hybrid of preaction and clean agent protection.
At Century Fire Protection, we’ve designed and installed all types, and we’ve seen firsthand how the right approach saves owners time, money, and frustration long-term.
If you’re not sure which path to take, let’s talk through your project. We’ll help you find the right balance between protection, compliance, and cost-efficiency.
Key Takeaway:
There’s no one-size-fits-all fire protection system. But understanding how single-, double-, and non-interlock preaction systems differ helps you make a smarter choice for your environment.
Whether you manage a data center, control room, or cold storage space, Century Fire Protection can help you select, design, and maintain a system that keeps your operations running safely — with confidence that your fire protection system is as responsive as your facility demands.
Watch the Full Expert Chat
Watch the full Expert Chat on-demand, or if you’d like to discuss which system makes the most sense for your facility, book a quick 10-minute chat with our fire protection specialists.
Related Resources
Data Center Fire Protection Made Easy with Cabinet-Mounted Preaction Systems
FAQs from Our Data Center Fire Protection Expert Chat
The information provided is for general informational purposes only. Every fire protection system is unique, with specific inspection, testing, and maintenance requirements determined by system type, manufacturer specifications, building use, and local regulations. Consult a qualified fire protection professional or your local Authority Having Jurisdiction (AHJ) to ensure compliance with applicable standards. Century Fire Protection assumes no liability for actions taken based on this content.