You know the call. and it’s the middle of winter… and now there’s potentially ice in the system, along with an impairment, and even possible system damage. For years, many crews handled that as a service problem first and a paperwork problem later. Under the 2026 edition of NFPA 25, that approach is hard to defend, because a frozen sprinkler system impairment follows the same rules as a closed control valve or a fire pump out of service.
The good news is that most freeze-ups are preventable. Also, the ones you can’t prevent go much more smoothly when your team and your customer already have a plan. This guide covers what changed, why dry and preaction systems freeze, and how to respond when they do.
What Does NFPA 25 2026 Change About Frozen Systems?
The 2026 edition keeps frozen systems in the impairment category, but it sharpens the trigger and the follow-up. Earlier editions applied to piping “found to be frozen.” The new language applies whenever piping contains ice.
The table below summarizes the 2026 provisions that matter most for winter work on dry and preaction systems.
| NFPA 25 2026 Section | Requirement | What It Means in the Field |
| 4.1.2.6.1 | Piping between the water supply and the discharge devices or hose connections that contains ice makes the system impaired. | Any ice in that path starts the impairment procedure. |
| 4.1.2.6.2 | Components that contain ice must be completely thawed out or replaced before the system returns to service. | Partial thaws don’t count as a restoration and some means must be made to ensure a complete thaw has happened. |
| 4.1.4.1 | Notification applies to both preplanned and emergency impairments. | A freeze-up you find at 2 a.m. still requires notification. |
In addition, Annex A.4.1.2.6.2 recommends inspecting thawed components for cracks and breaks. It also suggests a two-hour air test at 40 psi to find hidden leaks before a hydrostatic test.
Before you change contracts or reports, confirm which edition your AHJ has adopted. You can follow the edition history on the
Why Do Dry and Preaction Systems Freeze?
Dry and preaction systems freeze when water collects where it doesn’t belong. Most freeze-ups trace back to four causes.
- Water in low points. Condensate forms every time compressed air cools in the piping. A trip test also leaves water behind, so undrained auxiliary drains and drum drips hold water in the lowest part of the system.
- Air or nitrogen leaks. A leaky system makes the compressor run more, which pushes in more moist air and more condensate. Leakage can also drop pressure enough to trip the valve and fill the system in a freezing space.
- Pitch problems. Sagging or poorly pitched piping traps water no matter how often you drain it. Record those sections on your report so the owner can plan a correction.
- Cold valve rooms. The dry valve and its trim need heat. However, a failed unit heater, a propped-open door, or a missing insulation panel can freeze the riser itself.
Leakage and condensate feed each other, and both tend to get worse as systems age. That’s why winter prep starts long before the first hard freeze.
Some of the following items may already be a part of a NFPA 25 required inspection, while others are just some best practices for preventative maintenance. And doing these things doesn’t guarantee the system won’t freeze, but doing them does reduce that likelihood. Be sure to go over the list to ensure work is covered by the scope of work; if it isn’t, it’s an opportunity for you or your manager to have a conversation with the property owner.
- Trip-test while it’s warm. Run full or partial trip tests early in the fall, so the system has time to drain before temperatures drop.
- Drain every auxiliary drain and drum drip. Walk the system with a current drawing, and find every low point. Then label each drum drip in the field and on the drawing, so a new tech in January doesn’t have to hunt for the one above the dock door.
- Keep draining all season. Condensate keeps forming, so one drain in October won’t carry you through February. Drain again after cold snaps, trip tests, or any jump in compressor run time.
- Track air or nitrogen leakage. Log compressor run time and pressure trends where the equipment allows it. Next, find and fix leaks before winter instead of after the valve trips.
- Verify heat in valve rooms and enclosures. NFPA 25 has long required crews to check valve enclosures subject to freezing during cold weather. Check heaters, thermostats, doors, and low-temperature supervisory signals.
- Check antifreeze loops while you’re on-site. Many buildings only have anti-freeze systems in lieu of a wet or dry system or buildings with a primary wet system, might also have ancillary anti-freeze systems for vestibules or canopies. Confirm the solution meets current listing requirements, and that testing is up to date.
For a refresher on valve trim and gauges, Fire Tech’s Gauge and Valve Inspection and Testing course covers the components your crew checks on every winter visit. Also, our earlier post on Winter Preparation for Fire Sprinkler Systems includes field tips many owners still miss.
How Do You Handle a Frozen Sprinkler System Impairment?
Start the impairment procedure the moment you find ice in the piping. Even with good prep, freeze-ups happen, so walk through these steps in order:
- Confirm the impairment coordinator. Identify who is acting as the owner’s impairment coordinator. Often, it’s a facility manager who has never done it, so walk them through the process.
- Tag the impairment. Place impairment tags where the fire department and building staff will see them, typically at the fire department connection and the affected control valve.
- Make the notifications. Notify the AHJ, the fire department, the alarm-receiving facility, the insurance carrier, and the owner or their representative. Record who you emailed and/or called, and when.
- Decide on interim measures. Depending on the area affected and the AHJ’s expectations, a fire watch or other interim measures may be needed until the system is restored. But remember that a fire watch can become very expensive, very quickly. Put this on the owner, and if the contractor is providing, make sure to have a signed agreement and clear understanding of the potential costs.
- Thaw completely, or replace. Thaw with approved methods and never an open flame. Then inspect for cracked fittings and split pipe, and replace any damaged components. In environments that prevent thawing, impairments can go on for weeks and months, and other means must be made to facilitate the thawing.
- Test, restore, and close out. Test the affected portion, restore the system, and notify everyone that the impairment is over.
Fire Tech’s Freeze Machine article covers pipe freezing as a controlled repair method. The difference here is important: an uncontrolled freeze is a reportable impairment.
What’s at Stake for Your Company and Your Customer?
A frozen system handled outside the impairment procedure leaves a building unprotected and leaves your company exposed. If a fire breaks out while the fire department doesn’t know the system is down, someone will ask who should have made the call.
On the other hand, a clean response builds trust. When you show up with a plan, explain the requirement in plain terms, and hand the owner a clear list of what needs attention, you become the contractor they call first.
How Fire Tech Helps Your Team Prepare
Keeping up with a new edition while the calls stack up is hard, and every crew feels that pressure in November. For nearly 40 years, Fire Tech Productions has helped fire protection professionals master the standards they use every day. As a NICET Recognized Training Provider and ICC Preferred Education Provider, we offer 300+ courses, workshops, and study materials.
- Choose Your Training: From online courses and hands-on workshops to exam prep bundles and in-person training, we have the resources you need.
- Master the Codes: Gain the knowledge and confidence to learn fire protection standards, pass your exams, and confidently mitigate risks.
- Get Certified: Become a fire protection expert and propel your career.
Start with the online Inspection and Testing of Water-Based Systems Level I course, and keep the Inspection & Testing of Water-Based Systems Level I Fire Tab Set in your standard for quick reference. If your techs learn best with their hands on a valve, our Hands-On Workshops put them in front of real trim and real procedures.
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Frequently Asked Questions
Is a partially frozen system considered impaired?
Yes, if ice is in the piping between the water supply and the discharge devices. Section 4.1.2.6.1 of the 2026 edition ties impairment to ice in that path, and a frozen cross main or branch line can leave part of a building unprotected. Follow your impairment procedure for the affected area, and confirm the AHJ’s expectations for partial impairments.
Do I have to notify the fire department about a frozen system?
Yes, where the fire department requires it, and most do. Section 4.1.4.1 applies notification to emergency impairments, and a freeze-up is an emergency impairment. So, agree with the owner ahead of time on who makes the call and how it’s documented, then confirm the edition your jurisdiction has adopted.
How often should drum drips be drained in winter?
Drain them before freezing weather and as often as needed throughout the season. Condensate keeps forming as long as compressed air cools in the piping, so one drain in October may not be enough. Many contractors drain again after cold snaps, trip tests, or any increase in compressor run time.
Sources
- National Fire Protection Association, NFPA 25 Standard Development, NFPA 25, Standard for the Inspection, Testing, and Maintenance of Water-Based Fire Protection Systems, 2026 edition, Sections 4.1.2.6, 4.1.4.1, 4.1.5, A.4.1.2.6.2, and 14.3.1.
- Fire Tech Productions, Winter Preparation for Fire Sprinkler Systems.
- Fire Tech Productions, Freeze Machine.
