Testing, Inspection, Flushing, Commissioning and Documentation
What the exam tests
This domain tests the final stages of a project: flushing, hydrostatic testing, alarm and trip tests, commissioning, and the records the owner receives. Questions often ask for the test pressure, duration or document that proves the work was done.
Core rules and concepts
- Flushing. Underground mains must be flushed before connection to the sprinkler system. Flush at the required flow until the water runs clear, and do not flush through sprinkler heads or alarm devices.
- Hydrostatic test. NFPA 13 requires a hydrostatic test at 200 psi for 2 hours, or 50 psi above the working pressure where the working pressure exceeds 150 psi. Test with the system isolated, gauges at the low point, and all air vented.
- Air test. Dry pipe and preaction systems require an air test, commonly 40 psi for 24 hours with no loss, before the hydrostatic test or as required by the standard.
- Main drain test. Record static and residual pressures at the main drain and compare with the original results to detect supply deterioration.
- Trip test. Dry pipe, preaction and deluge valves require trip tests to confirm operation and alarm timing.
- Commissioning. Confirm valve positions, alarm and supervisory signals, pressure settings, spare heads, signage and owner training.
- Documentation. Complete the contractor's material and test certificate, as-built drawings, hydraulic calculations, O&M manuals and NFPA 25 inspection records. The owner needs these to maintain the system.
Worked example
A new wet-pipe system has a maximum working pressure of 175 psi. Because the working pressure exceeds 150 psi, the hydrostatic test pressure is 175 + 50 = 225 psi, not 200 psi. Fill the system, vent air, pressurize to 225 psi, hold for 2 hours and check for leaks and pressure loss. Record gauge readings, test duration, location and witnesses on the contractor's material and test certificate. Then complete the main drain test and alarm test.
Traps that cost marks
- Testing with compressed air instead of water for the hydrostatic test.
- Forgetting to flush the underground main before connection.
- Using 200 psi when the working pressure requires 50 psi above working pressure.
- Missing the contractor's material and test certificate or as-built drawings.