NFPA 13 System Components, Hydraulics, and Water Supply
Components and their functions
Know the purpose and behavior of the major components: control valves, check valves, alarm valves (wet and dry), preaction and deluge valves, pressure reducing and relief valves, flow switches, tamper switches, inspectors test connections, main drain, and the fire department connection. Understand the difference between wet, dry, preaction, and deluge systems and when each is appropriate - especially dry pipe for unheated spaces and preaction where water damage is a concern.
Hydraulics fundamentals
Be comfortable with the concepts behind hydraulic calculation: density, discharge from a sprinkler (Q = k√P), friction loss, elevation pressure, and the balance point between supply and demand. Understand supply curves, static and residual pressure, and how to read a waterflow test. Know that the fire department connection supplements but does not replace the supply, and understand the role of safety margins.
Water supply evaluation
Candidates should understand how to evaluate a supply: available flow at a given residual pressure, the effect of demand increases on residual pressure, and the need to account for private mains, tanks, and pumps. Know the difference between a flow test and a static-only reading, and why static-only data is insufficient.
Rule of thumb
A sprinkler's discharge is proportional to the square root of pressure - doubling pressure increases flow by about 41 percent, not double. Use that relationship to sanity-check answers.