You should switch from pressure to volume mode when

• A. More than half the rated capacity of the pump will be needed
• B. Discharge is blocked
• C. Suction pressure is low
• D. Engine temperature rises

Answer: (A)

Understanding the two pump modes helps you know when to switch. Pressure mode uses a governor to hold a target discharge pressure, adjusting flow to keep that pressure steady. Volume mode, on the other hand, aims to deliver a set flow (gpm) and lets the discharge pressure rise or fall with system demand.

Switching to volume mode when you expect to need more than about half of the pump’s rated capacity makes sense because trying to maintain a high fixed pressure at that level becomes hard and can lead to unstable flow or excessive engine load. By shifting to volume mode, you prioritize delivering the needed water volume over keeping a strict pressure, which is more reliable when large flows are required (for example, multiple lines or long runs).

Discharge blockage, low suction pressure, or rising engine temperature point to other issues or actions and don’t justify changing modes for the purpose of meeting high flow.