Throttling the discharge valve to approximately system flow should be done when?

• A. During peak demand
• B. After elevated storage is full
• C. Elevated Storage is not available
• D. During low demand

Answer: (C)

When elevated storage isn’t available, there’s no large buffer to smooth out demand fluctuations, so you throttle the discharge valve to roughly match what the system is actually consuming. This keeps the pump from delivering more water than is needed, helping to avoid excessive pressures, wasted energy, and rapid flow changes that can cause water hammer. Storage, when present, provides that buffer, so throttling to system flow isn’t as critical in that case. During peak demand you’d want more flow, not less; once storage is available or full you rely on that buffer to maintain pressure, so throttling to system demand isn’t the primary approach.