In a well pump handling hot water, when the pump is not in operation, those components above the static water level (SWL) are typically at a temperature substantially lower than when the pump is in operation. At start up the pump fills the column with hot water resulting in a lengthening of the column and shaft due to the thermal expansion. The difference in the change in length between the shaft and column resulting from the thermal expansion and other forces is a significant factor in pump design and selection