Pressure adjustment apparatus and method

A method of adjusting a pressure in a system, the system including a pump fluidly coupled to a chamber through a selector valve comprising a first valve block and a second valve block facing the first valve block, the pump having a pump body that defines a variable volume therein, the pump body further defining a first aperture and a second aperture therethrough, the first aperture and the second aperture being located at a distal end of the pump body such that the first and second apertures are in fluid communication with the variable volume, the method comprising:

• orienting the selector valve to a first position of a plurality of positions relative to the pump body by rotating the first and second valve blocks;
• flowing a first fluid from the variable volume in a first flow direction through the first aperture and into a first flow channel of the selector valve via a first check valve disposed in the first valve block by decreasing a volume of the variable volume, the first flow direction of the first fluid through the first aperture being a flow direction out of the variable volume;
• and
• flowing a second fluid from a fluid source in a second flow direction into a second flow channel of the selector valve via a second check valve disposed in the second valve block and through the second aperture by increasing the volume of the variable volume, the second flow direction of the second fluid through the second aperture being a flow direction into the variable volume.