A condensate pump includes a condensate reservoir, a liquid level float
sensor operable to sense a liquid level within the condensate reservoir,
and a pressure/vent valve including a pressure source, a pressure vent,
and a primary piston slidably supported in a primary cylinder and sliding
in the primary cylinder responsive to the liquid level sensor. A
secondary piston is slidably supported in a secondary cylinder and moves
responsive to a movement of the primary piston between a first
secondary-piston position wherein the pressure source is in communication
with a gas space of the condensate reservoir and the pressure vent is
isolated from the gas space, and a second secondary-piston position
wherein the pressure source is isolated from the gas space and the
pressure vent is in communication with the gas space.