Fire Sprinkler System Installation
What this domain tests
Installation covers turning approved drawings into a working system: pipe and fittings, hangers and bracing, sprinkler positioning around obstructions, flushing, and hydrostatic and acceptance testing.
Core rules
- Support piping at NFPA 13 hanger spacing, generally 12 ft for 1-inch and smaller pipe and 15 ft for larger pipe, with a hanger near the end of each branch line.
- Standard pendent and upright deflectors sit 1 to 12 in below the ceiling. Sidewall deflectors sit 4 to 6 in below the ceiling.
- Apply the obstruction rules. A sprinkler must throw water over an obstruction; where it cannot, add a sprinkler beneath the obstruction.
- Hydrostatically test at 200 psi for 2 hours, or at 50 psi above working pressure when working pressure exceeds 150 psi. Test the whole system, not a single section.
- Flush underground and aboveground piping before installing sprinklers, then perform main drain, alarm, and trip tests as acceptance tests.
- Provide seismic bracing, sway bracing, and flexible couplings where the building code requires them.
Worked example
A system has a working pressure of 175 psi. Because 175 psi exceeds 150 psi, the test pressure is 175 + 50 = 225 psi, held for 2 hours with no leakage. If the working pressure were 120 psi, the test would be 200 psi for 2 hours.
Traps
Hydro-testing before flushing; leaving sprinklers installed during a flush; reading pressure at the pump instead of at the high-point gauge; omitting sway bracing where seismic design applies; failing to record test pressure and duration.