A rotary positive displacement pump has a front-loading seal arrangement to better accommodate servicing and cleaning of the pump body. The pump includes a sliding seal subassembly disposed in a volume between a central portion of a rotor that is received on a shaft of a gear case and the hub of the pump body. A related method of modifying a rotary positive displacement pump enables a conventional pump with a rear-side seal arrangement to be transformed into a pump having a front-loading seal arrangement. In addition to the reduction of a dead zone in which turbulent flow does not occur by inclusion of the sliding seal subassembly, other modifications to the pump body improve the ability of the pump to be cleaned in place.