Which term is used to indicate the coefficient that governs sprinkler discharge capacity?

• A. Discharge characteristics
• B. K-factor
• C. NFPA 251
• D. Nominal K-5.6

Answer: (B)

The main idea is that a sprinkler’s ability to discharge water is governed by its K-factor, the discharge coefficient. The K-factor comes from the sprinkler head’s orifice and flow-path design and is used in the relationship Q = K * sqrt(P), where Q is the flow rate and P is the pressure at the head. This means that for a given head pressure, a higher K-factor head will deliver more water, so the K-factor directly controls discharge capacity. You’ll find the K-factor on the sprinkler’s data sheet or catalog, often listed as a value like 5.6 or 8.0. The other terms aren’t the standard coefficient: “discharge characteristics” is a vague descriptor, NFPA 251 is a separate standard, and “Nominal K-5.6” is just a specific example value, not the generic term used to indicate the discharge coefficient.