Do You Have a Dry Sprinkler System?
Full flow test due soon? Here's what most people miss...
What You Need to Know About the 3-Year Full Flow Trip Test
If your facility has a dry sprinkler system, do you know when the Full Flow Trip Test is due?
If you do—great.
If you don’t—pause here, go find your most recent Full Flow Trip Test report, then come back and finish reading. This could save you time, hassle, and confusion during your next survey.
Why Dry Sprinkler Systems Are Unique
Dry sprinkler systems operate differently than wet systems, and they come with specific and unique testing requirements. One of the most commonly requested documents during a Life Safety Code or Fire Marshal survey is the 3-Year Full Flow Trip Test.
Many facilities confuse the annual partial trip test with the full flow trip test—but they are not the same.
What to look for:
When reviewing your reports, don't stop when you see something like “trip time: 20 seconds.” That’s likely the annualpartial trip. What you need is a test labeled “Full Flow Trip Test” that documents the time it took for water to reach the inspector’s test connection.
Knowing the difference helps ensure you're meeting the correct requirement—and it will save time during audits or surveys.
When Is a Full Flow Trip Test Required?
There are two times when a Full Flow Trip Test is required:
Every 3 years, per NFPA 25
Whenever the dry sprinkler system has been altered
What Is a Full Flow Trip Test?
A Full Flow Trip Test simulates a sprinkler activation in a dry pipe system.
The valve at the sprinkler riser is tripped, allowing water to flow through the system piping and discharge from the inspector’s test connection, which is located at the farthest point from the riser.
The goal is to measure how long it takes for water to reach that end point—providing insight into how the system would perform in a real fire situation.
How Long Should It Take for Water to Reach the Inspector’s Test?
In healthcare settings, which are typically classified as Light Hazard, a 60-second delivery time is often referenced.
However, whether that time applies depends on system size and design—and here’s where the code comes in:
NFPA 13 – Standard for the Installation of Sprinkler Systems states:
7.2.3.3
A system size of not more than 500 gal (1893 L) shall be permitted without a quick-opening device and shall not be required to meet any specific water delivery requirement to the inspection test connection.
7.2.3.4
A system size of not more than 750 gal (2839 L) shall be permitted with a quick-opening device and shall not be required to meet any specific water delivery requirement to the inspection test connection.
What does this mean?
Systems under 500 gallons do not require a water delivery time.
Systems up to 750 gallons with a Quick-Opening Device (QOD) also do not require a water delivery time.
If a system under 500 gallons exceeds 60 seconds, it may indicate a design flaw or a restriction in the system. Likewise, a system with a QOD should trip faster due to the device’s function—if not, it may need evaluation.
What Does NFPA 25 Say About the 3-Year Full Flow Trip Test?
Here’s the requirement straight from the code:
NFPA 25 – 13.4.4.2.2.2*
Every 3 years and whenever the system is altered, the dry pipe valve shall be trip tested with the control valve fully open and the quick-opening device, if provided, in service.
Annex (Explanatory – Not Enforceable)
A.13.4.4.2.2.2
A full flow trip test generally requires at least two individuals, one of whom is situated at the dry pipe valve while the other is at the inspector’s test. If possible, they should be in communication with each other. A full flow trip test is conducted as follows:
The main drain valve is fully opened to clean any accumulated scale or foreign material from the supply water piping. The main drain valve then is closed.
The system air or nitrogen pressure and the supply water pressure are recorded.
The system air or nitrogen pressure is relieved by opening the inspector’s test valve completely. Concurrent with the opening of the valve, both testers start their stopwatches. If two-way communication is not available, the tester at the dry valve is to react to the start of downward movement on the air pressure gauge.
Testers at the dry pipe valve note the air pressure at which the valve trips and note the tripping time.
Testers at the inspector’s test note the time at which water flows steadily from the test connection. This time is noted for comparison purposes to previous tests and is not meant to be a specific pass/fail criterion. Note that NFPA 13, Standard for the Installation of Sprinkler Systems, does not require water delivery in 60 seconds for all systems.
When clean water flows, the test is terminated by closing the system control valve.
The air or nitrogen pressure and the time elapsed are to be recorded as follows:
a. From the complete opening of the test valve to the tripping of the valve
b. From the complete opening of the inspector’s valve to the start of steady flow from the test connectionAll low-point drains are opened and then closed when water ceases to flow.
The dry pipe valve and quick-opening device are reset, if installed, in accordance with the manufacturer’s instructions, and the system is returned to service.
For dry pipe systems that were designed and installed using either a manual demonstration or a computer calculation to simulate multiple openings to predict water delivery time, a full flow trip test from a single inspector’s test connection should have been conducted during the original system acceptance and a full flow trip test from the single inspector’s test should continue to be conducted every 3 years. The system is not required to achieve water delivery to the inspector’s test connection in 60 seconds, but comparison to the water delivery time during the original acceptance will determine if there is a problem with the system.
A Common Misunderstanding: The 60-Second Rule
One of the most common misconceptions about the Full Flow Trip Test is the belief that water must reach the inspector’s test connection in 60 seconds or less—but that is not a requirement in NFPA 25.
Here’s what the codes actually say:
NFPA 25 does not require a 60-second water delivery time for Full Flow Trip Testing.
That 60-second benchmark is found in NFPA 13, which applies to system design and installation, not ongoing inspection and testing.
Surveyors may reference the 60-second rule, but if they do, ask for clarification and request the code section in NFPA 25 that requires it (there isn’t one).
System under 500 gallons → No water delivery time is required, even without a quick-opening device.
System up to 750 gallons with a Quick-Opening Device (QOD) → No water delivery time is required.
If your system meets either of these exceptions, and your delivery time exceeds 60 seconds, it does not automatically mean you’re out of compliance.
Pro Tips to Stay Ahead
Know the exact date of your last 3-Year Full Flow Trip Test.
Be able to explain the difference between the annual partial trip and the 3-year full flow trip.
Organize your sprinkler reports clearly and by test type.
During surveys, if questioned about timing, ask for code reference and point out the applicable system exemption based on NFPA 13.
Remember: NFPA 25 governs the testing—not the installation timelines.
Perform the 3 year test in late spring to give the system time to clear or dry out so there is a less likely chance of a sprinkler pipe freeze from condensation left over.
How I Can Help
Staying ahead of Life Safety Compliance doesn’t have to be overwhelming. At Dustin Phillips Consulting, I make it easier for your team to understand what’s required, prepare for surveys, and improve safety across your facility.
Whether it’s mock surveys, staff training, or reviewing your documentation and fire plans, I bring real-world experience with practical solutions. My job isn’t just to point out issues—it’s to help you fix them before they become citations.
If you're looking for clear guidance and a partner who makes life safety surveys easier, let’s connect. A quick conversation today could save you a major headache tomorrow.
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