Commercial Fire Protection Guide
Fire Sprinkler System Types: Wet, Dry, Pre-Action & Deluge
Not every building uses the same sprinkler system. Here’s how the four main commercial system types differ, and which is typically used where.
Overview
Commercial fire sprinkler systems, governed by NFPA 13, fall into four main categories, each suited to different building conditions and hazard levels. The right type for a given space depends on temperature, hazard classification, and the consequences of an accidental discharge.
| System Type | How It Works | Typically Used For | Governing Standard |
|---|---|---|---|
| Wet Pipe | Water is held in the pipes at all times; a sprinkler head opens and discharges water immediately when heat activates it. | Most commercial and office buildings in heated spaces — the most common and lowest-cost system type. | NFPA 13 |
| Dry Pipe | Pipes are filled with pressurized air or nitrogen instead of water; when a head activates, air releases first, then water fills the pipe and discharges. | Unheated spaces where water could freeze, such as parking garages, loading docks, and cold storage. | NFPA 13 |
| Pre-Action | Requires two events — a fire detection signal and heat at the sprinkler head — before water enters the pipes and discharges, adding a layer of protection against accidental discharge. | Spaces with high-value or water-sensitive contents, such as data centers, museums, and archives. | NFPA 13 |
| Deluge | All sprinkler heads on the system are open at all times; when the fire detection system activates, water discharges from every head simultaneously. | High-hazard areas with fast fire spread risk, such as aircraft hangars and chemical or flammable liquid storage. | NFPA 13 |
Choosing the Right System
System selection is driven by the building’s occupancy, temperature conditions, and hazard classification, and is typically determined during the design phase by a licensed fire protection engineer in coordination with local code requirements. Many buildings use more than one system type — for example, wet pipe throughout heated office space and dry pipe in an attached unheated garage.
Frequently Asked Questions
Can one building have more than one sprinkler system type?
Yes. It’s common for a single building to use different system types in different areas depending on temperature and hazard — wet pipe in occupied office space and dry pipe in an unheated garage, for example.
Is pre-action the same as a clean agent system?
No. Pre-action sprinklers still use water and are a type of sprinkler system with an added detection step before discharge. Clean agent systems use a gaseous agent instead of water entirely. Some high-value spaces use both.
Which system type costs the most?
Dry pipe, pre-action, and deluge systems are generally more expensive than wet pipe systems due to additional components like air compressors, detection integration, and specialized valves. See our Cost Guide for the full list of cost factors.
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