If your commercial building has an antifreeze loop, the section of your fire sprinkler system filled with glycerin or propylene glycol to protect against freezing, summer is the time to test it. Not October. Not when the first freeze warning hits. Now, while contractors have availability and any repairs can be made without pressure. By the time most Front Range property managers think about antifreeze, the season has already closed in.
What Is an Antifreeze Loop and Who Has One?
An antifreeze loop is a portion of a wet-pipe sprinkler system filled with a liquid that won’t freeze at low temperatures. It’s used in areas that can’t be kept above 40°F: loading docks, parking garages, covered walkways, unheated storage areas, and cold rooms are the most common locations on Front Range commercial properties.
Instead of running a full dry-pipe system in those areas, contractors will often run a small antifreeze loop off the main wet-pipe system. The loop contains either glycerin or propylene glycol mixed with water at a specific concentration. If that concentration is wrong, too weak, the solution freezes, pipes burst, and you have a water damage claim and a sprinkler system that won’t protect the space.
At Denver’s altitude and with Front Range freeze cycles that can swing 50 degrees in 24 hours, an improperly maintained antifreeze loop is a real risk from October through April.
What NFPA 25 Requires
NFPA 25, the standard for inspection, testing, and maintenance of water-based fire protection systems, requires antifreeze concentration to be tested annually. It specifically requires that testing be done before the cold weather season. That means you need results in hand before October, not after.
The standard also requires multiple samples taken from different parts of the loop. Because antifreeze solutions can separate in the pipes over time, a single test from one location isn’t enough. A sample near the fill point may test fine while a sample at the far end of the loop is dangerously diluted. Your contractor must test multiple points and document each one.
Concentration limits under NFPA 25 are strict:
- Glycerin: 38% maximum
- Propylene glycol: 30% maximum
If any sample exceeds the allowable concentration, or falls below the freeze-protection threshold, the system must be completely drained and refilled with a correctly proportioned solution. That’s a bigger job than a simple test, and it requires a licensed contractor.
Why Summer Is the Right Window
Most property managers schedule antifreeze testing in September or October, which creates two problems. First, contractors are fully booked as everyone rushes to beat the deadline at the same time. Second, if your loop needs to be drained and refilled, you may be waiting days for a contractor to get back to you while early freezes are already happening at Front Range elevations.
June through August gives you:
- Open contractor schedules. No waiting.
- Warm weather. Easier working conditions for the technician.
- Time to fix problems. If the loop needs to be drained and refilled, or if a check valve or fitting needs replacement, you have weeks instead of days.
The Colorado Division of Fire Prevention and Control enforces NFPA 25 statewide. AHJs in Denver, Aurora, Fort Collins, and Boulder all expect systems to be maintained to the current standard. Getting your antifreeze test done now and documented means one less item to scramble on in the fall.
What the Test Involves
An antifreeze loop test is straightforward when the system is properly labeled and accessible. Here’s what to expect:
- Locate the antifreeze loop. It should be clearly marked. If it isn’t, that’s a problem worth fixing during this visit.
- Identify the antifreeze type. Glycerin and propylene glycol have different concentration limits. The system should have documentation showing which one is installed.
- Pull multiple samples. Your contractor will draw fluid from test points at different locations along the loop and test each one with a refractometer.
- Compare to freeze-protection charts. The refractometer reading is matched to a temperature chart to confirm the solution will stay liquid at the lowest expected temperature for your location.
- Document everything. Test results go in your inspection records. If your insurance carrier or AHJ asks for proof of maintenance, this is the document you need.
If any sample fails, the loop is drained and refilled. If fittings, check valves, or other components show corrosion or wear, those are addressed at the same time.
What to Check Before You Call
Before scheduling the test, do a quick walk of the affected areas:
- Find the antifreeze loop. Look for the labeled section of pipe in your loading dock, garage, or unheated space. If you can’t find it, that’s worth investigating.
- Check the documentation. Your inspection binder should have the last antifreeze test results and the type of antifreeze installed. If you don’t have records from the last two years, assume it needs attention.
- Look for visible issues. Corrosion at fittings, discoloration on the pipe, or any history of leaks in that section are all reasons to prioritize this test.
What This Means for Your Building
An antifreeze loop failure in winter is expensive and disruptive. Burst pipes, water damage to inventory or finishes, and a sprinkler system that’s out of service until repairs are made. It’s also preventable. A 30-minute test this summer closes the risk for the entire heating season.
Elevation Fire Protection tests and services antifreeze loops throughout Denver, Aurora, Boulder, Fort Collins, and Cheyenne. If you’re not sure when your loop was last tested or what antifreeze type is installed, we can check during the same visit as your annual NFPA 25 inspection. Call us at (720) 382-9669 or visit our service and repair page to schedule.