About Preaction Fire Sprinkler Systems

Fire protection is all about the management of risk.  Prudent risk management includes learning about and taking steps against both recognized risks and the unintended consequences of the protection options chosen.  UNITED Fire Systems is here to help with learning about and properly choosing the fire protection equipment you need.

Understanding Fire Sprinkler Systems

1.  The Wet-Pipe Fire Sprinkler System

Wet-pipe fire sprinkler systems are the simplest and most common.  Sprinkler heads that activate from the heat of a fire are attached to a pipe filled with water.  Easy to understand, right?  However, anything else that opens a sprinkler head or breaks the pipe can also release water and cause needless and expensive water damage.  These include:

  • Damage from freezing
  • Accidental physical damage of the pipe or fittings
  • Accidental physical damage to a sprinkler head

Wet-pipe sprinkler systems may not be appropriate where unnecessary water damage must be avoided.

2.  The Dry-Pipe Fire Sprinkler System

A common cause of damage to wet pipes is freezing.  Water expands when it freezes, so pipes can split and fittings can come apart.  Fire sprinkler systems in unheated areas and freezers overcome this problem by holding back the water at a valve until a sprinkler head activates from the heat of a fire.  The valve then opens, allowing the water to fill the pipe.  No problem from ice damage, but these systems are still susceptible to other physical damage, such as accidentally breaking off a sprinkler head.  Only one of the causes of pipe damage and unnecessary water damage has been addressed.

3.  The Preaction Fire Sprinkler System

When it is sensible and desirable to prevent any single source of damage from causing costly unwanted water discharge, the preaction fire sprinkler system is the answer.  These systems require a preliminary action—a preaction—before water discharges.

Here’s the idea:

  1. A fire will be sensed by a separate fire detection system (usually a smoke detector).
  2. After that preaction, a sprinkler head will active from the heat of a fire and release water.

Any one single unwanted event (one thing going wrong) cannot discharge water, including these scenarios:

  • Damage from freezing cannot discharge water, since the preaction (the smoke detector) has not taken place.
  • The same for accidental pipe damage (no smoke detector activation means no water discharge).
  • A broken sprinkler head (from accidental or deliberate damage) cannot discharge water since the smoke detector telling the valve to open has not activated.
  • Issues with the smoke detector (intact sprinkler heads keep the water in the pipe).

So, the preaction sprinkler offers maximum assurance that water will only discharge when there really is a fire.  This capability of preventing water damage from any single point of failure makes sense when evaluating the risks and consequences.

Preaction Systems: More to Consider

When it’s clear that preaction sprinkler fire protection is the best risk management strategy for you, don’t forget that it’s important to choose a system that is easy to specify, install, and maintain.

  • Your specification must include all components that make up a complete, working system, and those components have to be designed and approved to work together.
  • Coordination between the sprinkler contractor that works with the mechanical portion and the electrical contractor dealing with the fire alarm portion of the system is critical.
  • Maintenance of the system as a whole is vital to its continued functionality.

Sound complicated? It doesn’t have to be.

Simple and Complete: PREACTION-PAC

The PREACTION-PAC from UNITED Fire Systems assembles the critical components of a preaction fire sprinkler system into one pre-assembled package.  Here are the benefits:

  • All components specifically designed and specified to function as one unit.
  • Factory assembled, programmed, and tested—simply put in place, perform external hookups, and your system is ready.
  • Approved as a single functioning unit by Factory Mutual (FM)—your assurance of quality, functionality, and authority acceptance.
  • Each contractor’s work is clear—coordination made easy.
  • Just one set of instructions for commissioning and maintenance—again, responsibility is clear.
  • Expert in-house and field technical support from UNITED Fire Systems is always available to make every step clear and easy.

Want to Learn More?

Simply go to our PREACTION-PAC product page for:

  • Architect and engineer specifications.
  • Drawing details.
  • Data sheets.
  • Instruction manuals.
  • Engineering tools.


Contact Our Team
Did You Know?
  • Your wet-pipe sprinkler system may not be as filled with water as you expect it to be. A bubble of air may migrate to the highest point in the system, creating a very vulnerable location for internal pipe corrosion. That’s why NFPA 13 now requires that all new wet sprinkler systems be fitted with an air vent at the system’s highest point. This is a good investment for both new and existing systems. The UNITED Fire Systems Model AR-1 automatic air release device is Factory Mutual (FM) Approved for just this function. See here for more information, and take action to prevent damaging corrosion.