Sprinkler System Commissioning Protocol: NFPA 13 Acceptance Tests

Standard: NFPA 13 (2025), Chapter 29 (underground piping: Chapter 6)
Scope: Hydrostatic testing, flushing, operational tests, documentation
Reading time: 10 min

What Is Commissioning (Acceptance Testing)?

Commissioning a sprinkler system is the final test process carried out after installation is complete and before the building is put into use. NFPA 13 Chapter 29 defines the steps and the acceptance criteria. Commissioning follows this order:

1. Flushing and hydrostatic testing of the underground piping
2. Hydrostatic testing of the aboveground piping
3. Air test for dry and preaction systems
4. Flushing of the aboveground piping
5. Operational tests (waterflow, dry pipe valve trip, deluge system)
6. Main drain test
7. Backflow preventer test
8. Owner training and documentation

This article covers the technical details, acceptance criteria and field practice for each step.

1. Underground Flushing and Hydrostatic Test

Flushing Procedure

The underground main must be flushed before it is connected to the aboveground piping. Flushing removes sand, gravel, weld slag and other debris from inside the pipe.

Flushing velocity: the velocity inside the pipe must be at least 3.0 m/s (10 ft/s). The flow needed to reach this velocity depends on the pipe size:

Source: NFPA 13-2025, Table 6.11.2.1.3 (extracted from NFPA 24 Table 10.10.2.1.3), flow required to produce a velocity of 10 ft/s (3.0 m/s). In systems supplied by a fire pump, the pipe is flushed at the greater of the Table 6.11.2.1.3.2 flow and the system demand from the hydraulic calculation; if the water supply cannot deliver that flow, at least 150 percent of the rated pump capacity is used, and if that is not possible either, the greater of the rated pump capacity and the system demand (6.11.2.1.3.2 (B), (C)).

Duration: flushing continues until the water runs completely clear; there is no fixed duration. In the field 5–15 minutes is usually enough, but large systems can take longer.

Critical point: if the aboveground piping is connected without flushing, debris reaches the sprinklers and blocks them. This is one of the most common causes of system failure.

Hydrostatic Test of the Underground Piping

• Test pressure: 13.8 bar (200 psi) or working pressure + 3.4 bar (50 psi), whichever is greater, read at the gauge at the lowest elevation (6.11.2.2.1, 6.11.2.2.3)
• Duration: 2 hours
• Acceptance criterion: pressure held within ±0.3 bar (±5 psi) and no visible leakage (NFPA 13-2025, 6.11.2.2.1 and 6.11.2.2.2)

2. Aboveground Hydrostatic Test

Test Procedure

All aboveground piping and attached appurtenances subjected to system working pressure are hydrostatically tested (29.2.1.1).

• Test pressure: 13.8 bar (200 psi); where the working pressure exceeds 10 bar (150 psi), working pressure + 3.4 bar (50 psi) (29.2.1.3). In systems with a fire pump, the working pressure is the pump churn pressure plus the maximum static pressure of the water supply (29.2.1.4). The pressure is read at the lowest point of the system (29.2.1.6)
• Duration: 2 hours
• Acceptance criterion: no loss of pressure, determined by a drop on the gauge or by visible leakage (29.2.1.2)

Important: the pressure is measured at the lowest point of the system; because of elevation, the pressure on upper levels can be below 200 psi (29.2.1.6). For example, with 200 psi on the lowest floor, seeing about 185 psi 10.5 m higher is normal (1 bar ≈ 10.2 m of water column).

Testing in Sections

On large projects the system can be commissioned floor by floor or section by section; portions that can be isolated may be tested separately (29.2.1.6). Each section is tested on its own and records are kept. This fits the project schedule, but a general test should be repeated once the whole system is complete.

Testing Modifications

Modifications to an existing system are also subject to testing:

3. Air Test for Dry and Preaction Systems

Dry pipe and double-interlock preaction systems receive an air pressure leakage test in addition to the hydrostatic test (29.2.2.1):

• Test pressure: 2.8 bar (40 psi)
• Duration: 24 hours
• Acceptance criterion: any leak that results in a loss of pressure above 0.1 bar (1.5 psi) in 24 hours is corrected

Cold weather: where weather conditions do not allow testing with water, this air test may be carried out temporarily; it does not replace the hydrostatic test, which must still be performed (29.2.1.5).

Piping specially investigated and listed for use in dry and double-interlock preaction systems may be tested in accordance with its listing (29.2.2.2).

4. Main Drain Test

Purpose

The main drain test verifies the condition of the water supply: it shows that water can reach the system and that the pressure is adequate.

Procedure

1. Record the static pressure (system full, no flow)
2. Open the main drain valve fully and keep it open until the system pressure stabilizes (29.2.3.4.1)
3. Record the residual pressure during flow; the static and residual pressures are written on the contractor’s material and test certificate and on the general information sign (29.2.3.4.2)
4. Close the valve and check that the static pressure returns

With a fire pump: the main drain test should be carried out with the pump running.

Acceptance Criterion

The residual pressure is compared with the value in the hydraulic calculation report. If the residual pressure is lower than the calculated value, there may be a problem with the water supply (a weakened supply, an obstruction, a partly closed valve).

5. Waterflow Alarm Test

Inspector’s Test Connection

Waterflow detecting devices are tested by flowing water through the inspector’s test connection, and an audible alarm must sound on the premises (29.2.3.1); where a fire alarm system monitors waterflow, the alarm signal must be produced in accordance with the applicable fire alarm code (29.2.3.1.1):

• Wet systems: the test connection is at the most remote point downstream of the flow switch
• Dry systems: the test connection is on the most remote branch line

Acceptance Criteria

The criterion is the same in both cases: any flow equal to or greater than that from a single automatic sprinkler of the smallest K-factor installed on the system must produce an audible alarm on the premises, lasting until the flow stops (NFPA 13-2025, 7.7.1, 7.7.2).

Practical note: with a test and drain valve, the main drain test and the waterflow alarm test can both be done from the same point.

6. Dry Pipe Valve Trip Test

Dry pipe systems receive a working test by opening the inspector’s test connection; the time for the valve to trip and the time for water to discharge from the test connection are measured (29.2.3.2.1, 29.2.3.2.3). Water delivery time requirements (8.2.4):

QOD: quick-opening device. For systems where water delivery time is demonstrated by calculation (8.2.4.3), Table 8.2.4.3.2 applies by hazard (e.g. 50 s for ordinary hazard, 40 s for high-piled storage); systems verified by calculation are not separately subject to a time requirement at the acceptance test (29.2.3.2.3.2).

Accepted methods of demonstrating water delivery time:

1. Single test connection
2. Multiple test connection manifold
3. Calculation with a listed computer program

Air filling: the system must reach the required pressure within 30 minutes of the air supply being opened; for systems maintained at -15 °C or colder, the time is 60 minutes (29.2.3.2.4.1, 29.2.3.2.4.2).

7. Deluge and Preaction System Test

Test Steps

Automatic operation of deluge and preaction valves is tested in accordance with the manufacturer’s instructions; manual and remote control operation, where present, is also tested (29.2.3.3.1, 29.2.3.3.2):

1. Manual trip test: pull station / manual release
2. Automatic trip test: detector or pilot line
3. Remote trip test (where provided)
4. Full-flow deluge test: a gauge at the most remote sprinkler is recommended

Test Certificate Requirements

The test certificate must confirm that:

• Supervision of the detection line is working
• The valves operate correctly
• The system is in a testable condition

8. Backflow Preventer Test

Forward Flow Test

The backflow preventer is subjected to a forward flow test to confirm that it operates correctly; the minimum test flow is the system demand, including hose allowance where required (29.2.5.1, 29.2.5.2):

• The result is recorded on both the underground and the aboveground test certificate
• A flow equal to the system demand is passed through the backflow preventer
• The pressure loss is measured and compared with the manufacturer’s data

Note: this test is done once at acceptance and then repeated annually under NFPA 25.

9. Final Inspection and System Readiness

Visual Checklist

The final site walk checks the following:

Installation compatibility:

• Is the system consistent with the owner’s certificate and the intended use?
• Where there is storage: are the approved storage arrangement, rack layout, storage height, commodity class and pallet type documented?
• Are there obstructions or structural changes that were not present at the rough-in inspection?

Sprinklers:

• Are the escutcheons fitted?
• Have protective caps and straps been removed? (29.1.1)
• Have any sprinklers been painted? (painting is prohibited)

Heat sources:

• Are radiant heaters where the drawings show them?
• Are the temperature ratings of sprinklers near fireplaces and supply diffusers appropriate?

Spare Sprinkler Stock

Spare sprinklers must match the types, orientations and temperature ratings installed (16.2.7.2, 16.2.7.5); they must be kept in a cabinet where the temperature never exceeds the maximum ceiling temperature permitted for the sprinklers inside (16.2.7.3); and the cabinet must contain a sprinkler wrench for each sprinkler type (16.2.7.6) and a list of the sprinklers installed (16.2.7.7).

10. Documentation Requirements

Contractor’s Material and Test Certificate

Once commissioning is complete, the contractor prepares the following documents (29.1.1):

1. Underground certificate: flushing completed, hydrostatic test passed
2. Aboveground material and test certificate: all components listed, tests recorded
3. Hydraulic calculation report: design density, design area, water demand
4. As-built drawings: the installation as actually built

Signs and Tags

Permanent metal or rigid plastic signs must be provided at the following valves:

Owner Training

The contractor must train the owner before the system is put into service:

• How the system works
• NFPA 25 maintenance requirements
• Manufacturer’s instructions for the products the contractor installed
• What to do in an emergency (fire department, maintenance contractor contacts)

Documents handed to the owner:

• A copy of NFPA 25
• Manufacturer’s instructions for the installed products
• System drawings
• Hydraulic calculation report
• Test certificates

Field Practice: Common Mistakes

Commissioning Checklist (Summary)

• ☐ Underground piping flushed (until the water runs clear)
• ☐ Underground hydrostatic test: 200 psi (or working pressure + 50 psi), 2 hours, ±5 psi
• ☐ Aboveground hydrostatic test: 200 psi, 2 hours, no loss
• ☐ Dry/preaction air test: 40 psi, 24 hours, no more than 1.5 psi loss
• ☐ Main drain test: static and residual pressures recorded
• ☐ Waterflow alarm test: ≤ 100 s for an electrical device, ≤ 5 min for a mechanical device (7.7.1, 7.7.2)
• ☐ Dry pipe valve trip test: water delivery time meets the table
• ☐ Deluge/preaction system test: manual and automatic release tested
• ☐ Backflow preventer forward flow test: system demand flow passed
• ☐ Visual check: escutcheons, paint, obstructions
• ☐ Heat sources and sprinkler temperature ratings checked
• ☐ Spare sprinkler stock: in the cabinet, listed, with wrenches
• ☐ All signs and tags fitted (permanent, corrosion resistant)
• ☐ Hydraulic design sign and general information sign at the riser
• ☐ Owner trained (NFPA 25 + manufacturer’s instructions)
• ☐ All test certificates completed and signed
• ☐ As-built drawings updated and handed over

References

1. NFPA 13 — Standard for the Installation of Sprinkler Systems, 2025 Edition, Chapter 29 (Systems Acceptance). National Fire Protection Association. https://www.nfpa.org/codes-and-standards/nfpa-13/standard-development/13

2. NFPA 24 — Standard for the Installation of Private Fire Service Mains and Their Appurtenances, 2025 Edition, Table 10.10.2.1.3 (Flushing Flow Rates). National Fire Protection Association. https://www.nfpa.org/codes-and-standards/nfpa-24/standard-development/24

3. NFPA 25 — Standard for the Inspection, Testing, and Maintenance of Water-Based Fire Protection Systems, 2026 Edition. National Fire Protection Association. https://www.nfpa.org/codes-and-standards/nfpa-25/standard-development/25

4. NFPA 72 — National Fire Alarm and Signaling Code, 2025 Edition. National Fire Protection Association. https://www.nfpa.org/codes-and-standards/nfpa-72/standard-development/72

5. BOABC — Field Inspection / Acceptance Testing of Fire Sprinkler Systems, Matt Osburn (2024). British Columbia Building Officials Association. https://boabc.org/wp-content/uploads/2024/06/Acceptance-Testing-Commisioning-of-Sprinkler-Systems-Matt-Osburn.pdf

6. NFPA 20 — Standard for the Installation of Stationary Pumps for Fire Protection, 2025 Edition. National Fire Protection Association. https://www.nfpa.org/codes-and-standards/nfpa-20/standard-development/20

7. ASME A17.1 — Safety Code for Elevators and Escalators. American Society of Mechanical Engineers. https://www.asme.org/codes-standards

8. FM Global — Property Loss Prevention Data Sheets. https://www.fmglobal.com/research-and-resources/fm-global-data-sheets

9. SFPE — Society of Fire Protection Engineers. Fire Protection Engineering Resources and Guides. https://www.sfpe.org

10. AWWA M17 — Installation, Field Testing, and Maintenance of Fire Hydrants. American Water Works Association. https://www.awwa.org/standards

Frequently Asked Questions

What is the hydrostatic test pressure for a sprinkler system?

Under NFPA 13-2025 29.2.1.1 the hydrostatic test pressure for a sprinkler system is 200 psi (13.8 bar), held for 2 hours; where the working pressure exceeds 150 psi, working pressure + 50 psi is applied. The pressure is read at the lowest point of the system and there must be no loss of pressure.

What velocity is required to flush sprinkler piping?

Under NFPA 13-2025 Table 6.11.2.1.3 (extracted from NFPA 24), the flushing flow must produce a velocity of at least 3.0 m/s (10 ft/s) in the pipe. Flushing continues until the water runs clear. For example, a 100 mm (4 in.) pipe needs 1,500 L/min (390 gpm).

What is a trip test on a dry pipe sprinkler system?

The trip test on a dry pipe system measures the time for the valve to trip and the time for water to discharge from the inspector’s test connection (NFPA 13-2025, 29.2.3.2). Where the system capacity exceeds 750 gal (2,839 L), water must reach a single-outlet test connection within 60 seconds (8.2.4.2). A quick-opening device (QOD) may be needed.

How is the backflow preventer tested in a sprinkler system?

The backflow preventer is subjected to a forward flow test to confirm that it operates correctly; the minimum test flow is the system demand, including hose allowance where required (NFPA 13-2025, 29.2.5). That flow is passed through the backflow preventer and the pressure loss is measured. The test is done once at acceptance and then repeated annually under NFPA 25.

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