While pumping ballast the Chief Mate reports there is a decrease in vacuum on the pump suction when drawing from a partially full saddle tank. Which of the following could be a possible cause?

Correct Answer: Option A — An air leak in the suction piping from the tank.

A decrease in suction vacuum indicates that the pump is drawing air rather than liquid. An air leak in the suction piping allows atmospheric pressure to enter the system, which reduces the vacuum level and prevents the pump from maintaining a prime, especially when drawing from a partially full tank.