An all-polymer reciprocating pump (100) is contemplated. The pump body (160) receives a sliding insert (170) that may be locked in a down position to minimize the extension and profile of the actuator (120) while the pump (100) is not in use (e.g., for purposes of shipping in e-commerce). Projections (171) slide within guides (181) formed on an insert housing (180). Even in this down locked position, minimal compression is applied to the biasing members (130) so as to avoid fatigue, wear, and/or failure of the plastic components.