The Fire Sprinkler Winterization Checklist Every Facility Manager Needs by November 1

SEASONAL CHECKLIST

By the Ironsmith Fire Engineering Team · Memphis, Nashville, Houston

Quick facts

• 40°F is the line. Any space with water-filled sprinkler pipe has to stay at or above 40°F. NFSA, FM Global and major insurers all work from that number.
• Dry systems aren’t freeze-proof. Water from trip tests and condensation settles in low points. NFPA 25 calls for draining them before freezing weather and as needed after.
• Valve rooms get checked every day. In cold weather, NFPA 25 calls for daily checks of dry pipe valve enclosures, or weekly if the enclosure has a low temperature alarm.
• Antifreeze gets tested every year. The test comes before freezing weather. Existing systems also had to move to listed antifreeze by September 30, 2022.
• The fire pump room needs heat too. Electric pump rooms stay above 40°F. Diesel pump rooms run warmer.
• A frozen system is an impaired system. NFPA 25’s impairment rules apply, and a long outage can mean a fire watch.
• November 1 is a target, not a code date. It’s simply a way to finish before the first hard freeze instead of during it.

How to winterize a fire sprinkler system before the first hard freeze

Freeze-ups are quiet. Water in a cold pipe turns to ice and expands. A fitting cracks or a pipe splits, and nothing happens. Then the building warms up, the ice melts, and water runs until someone finds it. Now you’ve got a flooded space and a sprinkler system that’s out of service.

Most of that is preventable. The work isn’t complicated, but it has to happen before the cold, not after the first bad night.

Why November 1? In Memphis, the National Weather Service puts the average first fall freeze in early to mid November, depending on where you are in the metro. An average isn’t a promise. Some years it comes sooner. Treat November 1 as your finish line in Nashville too. It’s not a code deadline. It’s just a date that keeps you ahead of the weather.

Houston gets a pass most winters. Not every winter. The February 2021 winter storm brought a spike in frozen and burst fire sprinkler systems across Texas, and engineers reviewing the damage afterward found backflow preventers that froze too. Hard freezes do hit the Gulf Coast. When one comes, any sprinkler pipe in an unheated space is exposed, so the checklist still applies.

Work through the areas below in order. Each one ends with what to check.

Building envelope and heat

Most freeze-ups start with a building problem, not a sprinkler problem. A door propped open. A broken window in a stairwell. A thermostat turned down over a holiday shutdown.

• Walk every space that has sprinkler pipe, including attics, crawl spaces, soffits and above ceilings.
• Find the cold spots: vestibules, stairwells, unoccupied areas, skylights and poorly insulated walls. NFSA flags all of them.
• Seal gaps around doors, windows and skylights, and fix broken glass.
• Service the heating equipment that serves sprinkler spaces before the season starts.
• Set a minimum temperature for vacant and seasonal spaces. Keep the heat on. Insurers like FM Global recommend a written plan for what happens if the heat fails.
• Assign someone to watch the forecast. FM Global notes that a day’s warning can make a big difference.

Wet pipe systems

A wet system is water in the pipe, all the time. It’s simple and fast. It also can’t take a freeze. If you’re not sure which type you have, our guide to wet vs dry sprinkler systems covers the difference.

• Confirm every area with wet pipe holds 40°F on the coldest night, not just the average day.
• Look for wet branch lines that run into unheated spaces: canopies, docks, attics and exterior walls.
• Check insulation on pipe near exterior walls and roof decks. Insulation slows heat loss. It doesn’t create heat.
• Drain exposed wet piping that’s been taken out of service, as insurers like Zurich recommend.
• Report any cold space with wet pipe now. The fixes, from added heat to dry sprinklers, take time.

Dry systems and low point drains

Dry systems protect the cold spaces. But a dry system is never fully dry. Trip tests push water into the pipe, and compressed air brings condensation with it. That water settles at the low points. When it freezes, it can split the drain or the pipe and trip the system.

Draining low points

NFPA 25 calls for operating low point drains before freezing weather and as needed after that. After a dry system operates or gets trip tested, NFSA’s reading of the standard is to open the drains daily until several days pass with no water, then back off to weekly or longer.

• Drain every low point and auxiliary drain, also called drum drips, before November 1.
• Respect the valve sequence on drum drips. They work like an airlock, and opening both valves at once dumps system air and can trip the dry valve. If your staff hasn’t been trained on it, leave it to a technician.
• Keep draining through the season. Some insurers ask for weekly checks.
• Log each drain, date and the amount of water that came out.

Our post on purging a dry system before winter walks through the process in more detail.

Air and valve setup

• Confirm system air or nitrogen pressure is at the correct setting.
• Check that the air compressor or nitrogen generator cycles normally and the low air alarm works.
• Confirm the dry pipe valve’s priming water level is correct.

Valves, risers and the fire department connection

The valve room is the heart of a dry system, and it’s a wet space. The water sits right below the dry pipe valve. If that room freezes, the whole system’s in trouble.

• Confirm heat in every dry pipe, preaction and deluge valve room or enclosure.
• During cold weather, check enclosures daily to confirm they hold 40°F. NFPA 25 allows weekly checks if the enclosure has a low temperature alarm.
• Inspect any low temperature alarm at the start of heating season, and test that the signal reaches your monitoring company.
• Check riser rooms on outside walls. They lose heat fast.
• At the fire department connection, confirm the caps are on and the automatic drain, often called a ball drip, works. It lets water drain out of the pipe between the connection and its check valve so it can’t freeze there.
• Keep the connection and the control valves clear and reachable all winter.

Fire pump room

A fire pump that can’t start is a sprinkler system that can’t do its job. The pump room has its own heat rules.

• Keep an electric fire pump room above 40°F. NFPA 20 sets that floor.
• Keep a diesel pump room warmer. Sources commonly cite 70°F unless the engine has listed heaters. Check the engine maker’s requirement.
• Service the room’s heater before the season, and confirm louvers and doors close tight.
• Check that any pump room temperature alarm signals correctly.
• Keep up the weekly pump runs through winter. They’re also a good time to check room temperature. See our NFPA 25 inspection schedule for the full list of pump tasks.

Backflow preventers and exposed piping

The 2021 Texas storm put backflow preventers in the spotlight. An engineering review in Consulting-Specifying Engineer found that many outdoor units had only an insulating blanket or a frost-proof cover, and that wasn’t enough.

• Inspect every outdoor backflow assembly and its enclosure.
• Check that insulated enclosures close fully and any heat source inside works.
• Treat a blanket as a stopgap, not a fix. For repeat problems, ask about an insulated, heated enclosure or moving the device inside.
• Insulate exposed piping, and use listed heat tracing where heat can’t reach. Make sure someone gets an alert if the tracing fails.

Antifreeze loops

Antifreeze systems are wet systems filled with a solution that won’t freeze at the expected low temperature. They’re common on small exposures like canopies and vestibules. The rules on them have changed.

• Test the solution every year before freezing weather. Samples get pulled from more than one point in the system.
• Confirm the solution is listed. NFPA 25 required existing systems to use listed antifreeze by September 30, 2022.
• If your loop still holds older glycol or glycerin, or you don’t know what’s in it, have it evaluated before winter.
• Never top off an antifreeze loop with water or a mix of your own. Listed solutions come factory premixed.

Documentation and the fire watch plan

Paperwork won’t stop a freeze. It’ll tell you what got done, and it’ll save time on the worst night of the year.

• Keep records of every drain, temperature check, antifreeze test and heater service. NFPA 25 puts record keeping on the owner.
• Post a short list of who to call if a pipe freezes or breaks: your sprinkler contractor, alarm company, and the person who can shut off the water.
• Label the control valves so staff can find the right one fast.
• Name an impairment coordinator. NFPA 25 makes a frozen or shut down system an impairment, with tags and notifications to the fire department and your insurer.
• Plan your fire watch now. Under NFPA 25, a system out of service for more than 10 hours in a 24 hour period calls for steps like a fire watch or evacuating the area. Your fire marshal has the final say.

Get your winterization done before the cold

You can work this checklist in house, and plenty of facility teams do. Where it gets hard is the parts that need a licensed hand: trip tests, antifreeze sampling and replacement, valve and alarm checks, and repair work when the walk-through finds a problem.

That’s where we come in. Our fire sprinkler maintenance team can line up winterization with your regular inspections, so the low point drains, valve rooms, pump room and antifreeze all get covered in one visit. If something’s broken, the same team fixes it. One call, one accountable team, and no finger-pointing between vendors.

Frequently asked questions

How do you winterize a fire sprinkler system?

Keep every space with water-filled sprinkler pipe at or above 40 degrees F, drain the low points on dry systems before freezing weather, test antifreeze loops, and confirm heat in valve rooms and the fire pump room. Seal drafty doors and windows, check backflow enclosures and exposed piping, and have a plan for a frozen or impaired system. NFPA 25 ties several of these tasks to the start of freezing weather, so finish them before the first hard freeze.

What temperature do fire sprinkler pipes freeze at?

Water freezes at 32 degrees F, but sprinkler pipe can freeze in a space that reads warmer, because spots near exterior walls, roof decks and open doors run colder than the room. That’s why NFSA, FM Global and insurers use 40 degrees F as the minimum for any space with water-filled sprinkler pipe. Wind and long cold stretches raise the risk.

How often should dry system low point drains be drained?

NFPA 25 calls for draining low point drains before freezing weather and as needed after that. After a dry system operates or is trip tested, NFSA advises draining daily until several days pass with no water, then moving to weekly or longer. Some insurers ask for weekly checks all winter. Log each drain and how much water came out.

Do fire sprinkler systems in Houston need winterization?

Yes. Hard freezes are rare on the Gulf Coast, but they happen. The February 2021 winter storm brought a spike in frozen and burst fire sprinkler systems across Texas, and outdoor backflow preventers froze too. Check attics, canopies, backflow enclosures and dry systems before a cold snap.

What should I do if my fire sprinkler pipes freeze?

Do not use an open flame to thaw a pipe. Call your sprinkler contractor, and be ready to shut off the water if the pipe breaks. A frozen system is an impairment under NFPA 25, so notify your fire department, insurer and alarm company, and plan a fire watch if the system will be out of service for an extended time. Have the system inspected and restored before you count on it again.

Winterization · Before November 1

Want it off your plate?

Tell us about your building. We’ll line up winterization with your next inspection, so drains, valve rooms, the pump room and antifreeze get covered in one trip.