The shut off head shall not exceed what percent of the rated head for any pump?

• A. 120%
• B. 140%
• C. 100%
• D. 150%

Answer: (B)

Shut-off head is the maximum head a pump can produce when there is no flow, read at zero flow on the pump curve. In sprinkler pump design, this limit is set as a percentage of the rated head to prevent dangerous overpressure when the discharge is closed. The standard limit is 140 percent of the rated head. Keeping the shut-off head under this limit protects piping, valves, and fittings from excessive pressure that can occur in dead‑head conditions, while still allowing the pump to operate safely across its range. If the shut-off head were higher, pressures could spike with no flow; if it were lower, the system might not reach required pressures or could overwork the pump at lighter loads. So, 140 percent is the correct safeguard.