Fire sprinkler antifreeze systems — what Washington building owners need to know about the 2012 code change

Many commercial buildings in Western Washington have antifreeze fire sprinkler loops installed before 2012 that are now non-compliant with NFPA 13. A plain-English guide to what changed, how to check compliance, and the three paths to fix it.

What an antifreeze loop is and where to find one

An antifreeze fire sprinkler loop is a section of the fire sprinkler system filled with a glycol-water mixture instead of plain water. The glycol prevents the water in exposed pipe from freezing during cold weather.

Antifreeze loops are installed wherever sprinkler pipe runs through an area that can drop below 40°F — the threshold below which plain water in a pressurized pipe will freeze and rupture the system. In Western Washington, the most common locations are:

• Covered entry canopies. Retail and office buildings with a covered drive-up entry, parking structure entries, and similar exposed overhead zones.
• Loading docks. Open or semi-enclosed dock areas where overhead doors are frequently open to outside air.
• Refrigerated spaces. Cold storage, walk-in cooler rooms, and freezer corridors.
• Parking garage decks. Multi-level garages where exterior decks are protected by sprinklers but are exposed to ambient temperature.
• Exterior overhangs and covered walkways. Connected to the building's sprinkler system but exposed to freezing temperatures in cold snaps.

If your building was constructed before 2013 and has any of these features, there is a reasonable chance you have an antifreeze loop — and a meaningful probability that it does not comply with the current NFPA 13 standard.

What changed in 2012

The 2010 edition of NFPA 13 made a fundamental change to how antifreeze solutions are permitted in fire sprinkler systems. The change took effect as AHJs adopted the 2010 and 2012 editions.

The trigger was a UL testing program that demonstrated a problem: certain antifreeze solutions — specifically ethylene glycol at any concentration and propylene glycol above defined concentration levels — can ignite or significantly accelerate fire spread when atomized through a sprinkler head that activates during a fire. A system designed to suppress fire was instead capable of contributing to it, depending on the antifreeze solution in the pipe.

The 2010 NFPA 13 response was categorical: all antifreeze solutions in new fire sprinkler systems must be "listed" solutions — solutions that have been formally tested and approved (by UL or FM Approvals) to confirm they do not ignite or contribute to fire spread when discharged through a sprinkler head.

Two additional rules followed:

1. Ethylene glycol is permanently prohibited in fire sprinkler antifreeze systems, at any concentration, in any system.
2. Existing systems with non-listed antifreeze solutions are required to be brought into compliance over time as AHJs enforce the adopted code edition.

What "non-compliant" looks like in practice

Before 2010, there was no requirement to use a listed solution. Sprinkler contractors and building engineers routinely used:

• Automotive antifreeze (ethylene glycol-based) — convenient and cheap, completely prohibited now
• Propylene glycol mixed at whatever concentration the installer calculated for the local freeze depth
• "Food-grade" propylene glycol without formal testing for fire sprinkler use
• Commercial glycol products not specifically listed for fire sprinkler applications

A building installed in the 1990s or early 2000s almost certainly has one of these solutions. The solution may still be in the pipe today, unchanged. The concentration may have drifted from the original mix due to dilution or water makeup over years of operation. And unless an NFPA 25 inspection contractor tested the antifreeze solution and flagged it as non-listed, the issue may have gone unnoticed through multiple inspection cycles.

The risk is not theoretical. An antifreeze loop with ethylene glycol or a non-listed glycol concentration will pass a visual inspection — it is not visible to the eye. It only becomes a problem when a head activates and the solution atomizes into a fire compartment.

The three compliance paths

If your building has an antifreeze loop that uses a non-listed solution, there are three ways to reach compliance:

Option 1: Drain and refill with a listed antifreeze solution. The existing loop is drained, flushed, and refilled with a UL-listed or FM-approved antifreeze solution at the correct concentration for the lowest expected ambient temperature. This is the least disruptive option and typically does not require a permit amendment unless the system configuration changes. The new solution must be documented on the riser room tag and tested annually per NFPA 25.

Option 2: Convert the zone to a dry-pipe system. The antifreeze loop is converted to a dry-pipe zone — the pipe is drained and pressurized with air or nitrogen instead of water. A dry-pipe valve controls water entry when a head activates. This eliminates the antifreeze issue entirely and has no ongoing chemical-testing requirement. The tradeoff: dry-pipe systems have a delay between head activation and water discharge (typically 30–60 seconds), and the dry-pipe valve, air compressor or nitrogen supply, and associated trim require their own annual maintenance. Conversion requires a permit in most jurisdictions.

Option 3: Convert to a pre-action system. A pre-action system holds the pipe dry, like dry-pipe, but adds a detection trigger (typically a smoke detector signal) before the valve opens. This is the most complex and most expensive option and is typically used only in spaces where accidental discharge would cause significant damage — data centers, archives, refrigerated spaces with expensive contents. Overkill for most entry canopies and loading docks.

For most Western Washington commercial buildings, Option 1 (listed solution refill) is the fastest path and the lowest-cost correction. Option 2 (dry-pipe conversion) makes sense when the zone is large enough that the antifreeze volume creates ongoing testing and chemical management overhead, or when the freeze-depth requirement exceeds what the listed solutions can cover.

What NFPA 25 requires for antifreeze systems

NFPA 25 Chapter 5 covers sprinkler systems and includes specific requirements for antifreeze loops. Key requirements for building owners:

Annual solution testing. A sample of antifreeze solution must be drawn from the lowest point of the loop at least annually. The sample is tested for freeze protection point (to confirm it can still protect down to the required temperature) and for pH (degraded glycol becomes acidic and accelerates internal corrosion). The results must be documented in the inspection report.

Listed solution verification. The NFPA 25 inspection contractor should confirm that the antifreeze solution in use is a listed type. If the solution type is unknown — which is common in older buildings without good records — a refill with a known listed solution is the fastest resolution. Guessing is not compliant.

Concentration adjustment. If the sample shows the freeze protection point has drifted from the required minimum (due to water dilution from makeup water or system additions), the concentration must be corrected. A solution that tested at -15°F protection five years ago may now protect only to 20°F after years of small water additions.

Building owners who have not received an antifreeze test result in their annual NFPA 25 inspection report — or who do not have records showing a listed solution was installed — should treat this as an open compliance question.

Washington State context

Pierce County and South King County jurisdictions have adopted the IFC editions that reference NFPA 13 2010 and later. This means:

• New antifreeze loops installed after local adoption must use listed solutions. Any contractor installing a new antifreeze loop with a non-listed solution after 2012 was non-compliant at installation.
• Existing systems are addressed on a compliance-on-inspection or complaint basis. There is no statewide rollout program for antifreeze compliance. If the AHJ inspector observes a non-listed solution or requests documentation and none exists, the building owner will receive a deficiency citation.

In practice, enforcement of existing-system antifreeze compliance is highest when:

• The building receives an NFPA 25 inspection from a contractor who performs a proper antifreeze sample and test
• The building is involved in a renovation or TI that triggers a new sprinkler permit and an AHJ walk-through
• The building receives a fire-marshal inspection for a certificate of occupancy or change of use

If you're going into a TI permit that touches the antifreeze loop zone, bring the compliance question to the sprinkler contractor before the permit is filed. Discovering it at rough-in inspection — when the AHJ asks for documentation of the listed solution — creates a schedule problem.

What to do now

If you're a building owner or facilities manager and you're not sure whether your antifreeze loop is compliant, the practical next step is straightforward:

1. Pull your most recent NFPA 25 inspection report. Look for an antifreeze section. If it shows a sample was taken, what solution was tested, and the results — you have baseline documentation. If the antifreeze section is blank, or if you don't have a report, that's the gap to close.

1. Ask the inspection contractor to confirm the solution type. If they cannot confirm the solution is a listed type (with documentation), schedule a refill with a listed solution. The cost of a loop drain, flush, and refill with listed solution is modest compared to the liability of a non-compliant antifreeze system.

1. Update the riser room documentation. After a listed solution is installed, the antifreeze type, concentration, and freeze-protection point should be noted on the system tag in the riser room and in the inspection records.

We carry listed antifreeze solutions and can perform a drain, flush, and refill as part of an NFPA 25 inspection response or as a standalone service. If you're not sure whether your system is compliant, a phone call is faster than a deficiency citation.

Last reviewed by Michael Berger, Owner · 1st Choice Fire · WA L&I #1STCHCF770OF