The hard freezes of a Midwest winter are on their way, and they will find every weak point in your dry sprinkler systems. A cold valve room, a low point that never fully drained, or a compressor that can’t keep up all lead to the same place once the temperature drops: frozen water and split pipe. Ensuring proper Freeze Protection measures can prevent these issues.
This checklist covers what facility and operations managers should have done on their dry systems before the cold arrives, along with the other cold-weather exposures that can take a sprinkler system offline.
The requirements in this checklist come from NFPA 25, the National Fire Protection Association’s standard for inspecting, testing, and maintaining sprinkler systems. This checklist references the 2023 edition, which is the edition tied to the 2024 International Fire Code. The edition that applies to your facility depends on what your state or local AHJ has adopted.
How a dry system freezes
Dry pipe sprinkler systems are built for spaces that can’t be kept above freezing, like attics, loading docks, unheated warehouses, canopies, and cold storage. Instead of water, the piping holds pressurized air, which keeps a valve closed and holds the water supply back in a heated valve room. When a sprinkler head opens in a fire, the air escapes, the valve trips, and water flows to the heads.
The design only works if the piping beyond the valve stays empty. That’s why NFPA requires dry systems to be kept dry at all times, and doesn’t allow one to be left full of water in freezing weather. A dry system freezes in a few predictable ways. One is condensation collecting at the low points in the piping and freezing. Another is when the system loses enough air pressure to trip on its own, filling the pipes with water in the coldest parts of the building. And the valve and the supply piping feeding it hold water at all times, so if the valve room isn’t properly heated, the valve or supply piping can freeze. Most items on the checklist below target one of these.
The pre-winter checklist
Check the heat in the dry valve room
The valve room is the one part of a dry system that has to stay warm. NFPA requires valve enclosures exposed to freezing to be checked every day during cold weather to confirm they’re holding at least 40°F. If the room has a low-temperature alarm, weekly checks are allowed, and the alarm itself has to be inspected at the start of each heating season.
Before the cold sets in, confirm the heater works and is set correctly, the door closes and stays closed, and nothing is letting cold air in. A heater that fails during a mild stretch is easy to put off. Then an overnight storm arrives, and the repair you postponed becomes a frozen valve.
Drain the low points
Even a dry system collects some water. Condensation from the compressed air settles at the low points in the piping, and residual water can remain after testing or a trip. Dry systems have drains at those spots, often called auxiliary drains or drum drips, so that water can be removed before it freezes and splits the pipe.
NFPA lists low-point drain maintenance as a required item for dry systems, and it requires the information sign at each system riser to show where those drains are. Have them drained before freezing weather sets in, and again after any trip test or activation. A large facility can have a long list of drains, some of them high overhead, so build the work into the schedule rather than leaving it for the first cold week.
Service the air compressor and air dryer
The compressor maintains the air pressure that holds the valve closed and keeps the pipes dry. NFPA requires compressors used with dry systems to be inspected, tested, and maintained according to the standard and the manufacturer’s instructions. Air dryers, which remove moisture from the air going into the piping, must be maintained according to the manufacturer’s instructions as well.
A compressor that’s struggling in October won’t get better in January. Have it serviced now, and confirm it holds pressure without running constantly.
Find and fix air leaks
Small pinhole leaks are common on dry systems, and a healthy compressor covers them. The trouble starts when leaks add up or a larger one develops, and the compressor has to run harder to keep pressure up. Going into winter with a known leak leaves the system with less margin when it’s needed most. Locate and repair leaks before the season, not after the first alarm.
Set a plan for low-air alarms
When a dry system’s compressor can’t keep up with air loss, the system sends a low-air alarm to the fire alarm panel. That alarm means pressure is already falling. If nothing is done, the system will eventually trip and fill with water, and in a freezing space, that water turns to ice and splits the pipe.
The alarm only helps if the person who hears it knows what it means. The people closest to the panel are often shift supervisors, maintenance techs, or security staff who may not be able to tell a low-air alarm from any other signal on the panel. Before winter, walk the staff who work near the panel through what to do when the alarm sounds:
- Recognize the low-air signal and understand that it needs action, not just silencing.
- Report it right away to a designated person, such as the facility or maintenance manager.
- Call your fire protection contractor to find and fix the cause.
- Keep the contractor’s service number posted at the panel.
Close out open deficiencies
Look back at your most recent inspection reports. Outstanding repairs on a dry system are easier to schedule and less disruptive to complete in mild weather than in the middle of a January emergency. The same goes for overdue tests. Testing that puts water into a dry system’s piping is far simpler to complete, and to fully drain afterward, before temperatures drop.
Other cold-weather exposures in your facility
Dry systems aren’t the only sprinkler piping at risk in winter. A few other exposures belong on the same pre-season walkthrough.
Wet pipe in cold spaces
Wet pipe systems hold water in the piping at all times. NFPA requires any area with water-filled sprinkler piping to be kept at 40°F or above, unless the piping is protected with an approved antifreeze solution. Watch for spaces that run colder in winter than they were designed to, like a storage area where the heat gets turned down or a room along an exterior wall.
Heat tracing and insulation
Where water-filled pipe runs through cold areas, it’s often protected by heat tracing, insulation, or frostproof casings. NFPA requires those protections to be inspected, tested, and maintained, and the protected pipe to be kept between 40°F and 120°F.
Antifreeze systems
Some wet systems are filled with an antifreeze solution instead of plain water. NFPA requires the solution to be tested every year at the start of the heating season, before freezing conditions arrive, to confirm it’s still at the right concentration and is a permitted type.
The building envelope
Dock doors left open through long loading cycles, broken windows, and heat shut off in idle areas can all drop the temperature around sprinkler piping. They’re operational habits rather than system problems, so make sure staff know which habits put your sprinkler systems at risk.
If a system trips or freezes
Even with good preparation, a system can still trip or freeze. When it does, the goal is to limit the damage and get protection restored quickly. If water is flowing from a tripped system or a broken pipe, get the system’s control valve closed and call your fire protection contractor right away. Water from a broken sprinkler pipe can also damage fire alarm components, so the impact can reach beyond the sprinkler system itself.
A system that’s out of service is an impairment, and NFPA has specific procedures for handling one, including tagging the impaired system. Your AHJ may also require a fire watch until protection is restored.
Get ahead of winter with Summit Fire Protection
Our local teams serve industrial, commercial, agricultural, and institutional facilities across the Midwest, Colorado, and Arizona. We inspect, test, and service dry systems before the cold arrives, and we respond when a freeze takes a system down. Our technicians know the systems, the codes, and the AHJs in the communities where you operate, so pre-winter work gets done right and on schedule.
Contact Summit Fire Protection to schedule a pre-winter inspection of your dry sprinkler systems.