What is the term for the condition of zero flow when the fire pump is running but the only water passing through the pump is a small flow discharged or used for cooling?

What is the term for the condition of zero flow when the fire pump is running but the only water passing through the pump is a small flow discharged or used for cooling?

• A. Peak Load
• B. Alternate Power
• C. Open Motor
• D. No Flow (Churn, Shutoff)

Answer: (D)

The main idea here is recognizing a no-flow condition. When a fire pump is running but virtually no water is moving through the pump—only a small amount used for cooling or leakage—the pump is delivering head without delivering flow. This state is described as no flow, and it’s often called churn or shutoff because the impeller is turning against almost a closed discharge. In this scenario the pump reaches its shutoff head, the maximum pressure it can develop with zero flow, which is important to know for protection and piping design. This matters because running in no-flow for an extended time can cause overheating of the pump or motor since there’s little fluid circulating to carry away heat, even though pressure is high. It’s distinct from actual flow where the pump operates along its curve under system demand. Other terms listed don’t describe this condition. Peak load is about electrical demand, alternate power is about power sources, and open motor isn’t the standard term for the situation described.

The main idea here is recognizing a no-flow condition. When a fire pump is running but virtually no water is moving through the pump—only a small amount used for cooling or leakage—the pump is delivering head without delivering flow. This state is described as no flow, and it’s often called churn or shutoff because the impeller is turning against almost a closed discharge. In this scenario the pump reaches its shutoff head, the maximum pressure it can develop with zero flow, which is important to know for protection and piping design.

This matters because running in no-flow for an extended time can cause overheating of the pump or motor since there’s little fluid circulating to carry away heat, even though pressure is high. It’s distinct from actual flow where the pump operates along its curve under system demand.

Other terms listed don’t describe this condition. Peak load is about electrical demand, alternate power is about power sources, and open motor isn’t the standard term for the situation described.