PUMP ASSEMBLY

A pump has power and fluid ends wherein one or more of the drive rods are offset from the plungers. An offset coupler connects a drive rod to an offset plunger. A method includes connecting the offset power end to the standard fluid end using the offset coupler. A repair and maintenance system includes inventories of standard fluid ends, power ends including offset power ends, and adapters, and a population of in service pumps, whereby the pumps can be repaired by removing and replacing the power ends from inventory using the adaptor where the replacement power end unit is offset. Another method includes removing and replacing the power end with one from the inventory, wherein the adapter is used in the case of an offset power end, whereby the offset and standard power ends may be used interchangeably.