Deflation via Dump Valve / Flat E-valve / Flat Valve

BCs have either one, two or three additional dump valves / Flat E-Valves / Flat Valves, depending on the specific BC model. Their primary function is to relieve excess air pressure inside the bladder, but some may be equipped with a knob and cord assembly and can be opened manually by pulling on the knob and cord assembly to quickly dump air.
To dump air as quickly as possible, always use the dump valve / Flat E-Valve / Flat valve at the highest point in the water column. For example, the lower rear valve works best while making a headfirst descent, or swimming in a facedown position; the right shoulder valve works best when in an upright position.