What indicates that the pump has been successfully primed?

The indication that the pump has been successfully primed is demonstrated by positive pressure on the discharge gauge. When a pump is properly primed, it creates a solid column of water, allowing the fluid to be moved efficiently from the intake to the discharge. This results in the discharge gauge showing positive pressure, reflecting that the pump is operating correctly and water is being pushed out under pressure.

Each choice provides different metrics. A decrease in the vacuum reading can sometimes indicate successful priming as it represents a reduction in air trapped in the pump, but it is primarily the establishment of discharge pressure that definitively indicates effective priming. The increase in engine temperature is generally related to engine performance rather than the pump status itself, making it less relevant for determining priming success. Therefore, monitoring the discharge pressure is the most direct and definitive method of confirming that a pump is primed and functioning as intended.