A backflow prevention device,,, comprising: a distal portion,, defining a distal opening; a proximal portion,, defining a proximal opening; a valve member positioned at a location between the distal portion,, and the proximal portion,,, the valve member including a valve flap,, with a first portion held between the distal portion,, and the proximal portion,,, with the first portion being trapped between the distal portion and the proximal portion as the distal portion and proximal portion are connected together, and a second portion automatically moveable from a first position substantially blocking fluid flow between the distal opening and the proximal opening, and a second position moved toward the proximal opening to permit fluid to flow between the distal opening and the proximal open upon application of a vacuum force to the valve member, with the first portion being a bottom end portion of the valve flap,, and the second portion being a top end portion of the valve flap,,; at least one valve retention member positioned between the proximal portion,, and the distal portion,,, the at least one valve retention member configured to engage the valve member to retain the valve member in a predetermined orientation relative to the proximal portion,, and the distal portion,,, with the at least one valve retention member including a connection protrusion; connecting means to secure the distal portion,, and the proximal portion,, together in permanent connection or in a connection arrangement in which the distal portion,, and the proximal portion,, are releasably engaged with each other; and alignment means for aligning the distal portion,, and the proximal portion,, relative to each other when connecting the distal portion,, and proximal portion,, together characterized in that: one of the proximal portion and the distal portion includes an axially aligned rib, and the other of the proximal portion and the distal portion including an axially aligned channel sized to receive the rib when the proximal and distal portions are connected together; and the connection protrusion of the at least one valve retention member extends at least partially through a thickness of the valve member. a distal portion,, defining a distal opening; a proximal portion,, defining a proximal opening; a valve member positioned at a location between the distal portion,, and the proximal portion,,, the valve member including a valve flap,, with a first portion held between the distal portion,, and the proximal portion,,, with the first portion being trapped between the distal portion and the proximal portion as the distal portion and proximal portion are connected together, and a second portion automatically moveable from a first position substantially blocking fluid flow between the distal opening and the proximal opening, and a second position moved toward the proximal opening to permit fluid to flow between the distal opening and the proximal open upon application of a vacuum force to the valve member, with the first portion being a bottom end portion of the valve flap,, and the second portion being a top end portion of the valve flap,,; at least one valve retention member positioned between the proximal portion,, and the distal portion,,, the at least one valve retention member configured to engage the valve member to retain the valve member in a predetermined orientation relative to the proximal portion,, and the distal portion,,, with the at least one valve retention member including a connection protrusion; connecting means to secure the distal portion,, and the proximal portion,, together in permanent connection or in a connection arrangement in which the distal portion,, and the proximal portion,, are releasably engaged with each other; and alignment means for aligning the distal portion,, and the proximal portion,, relative to each other when connecting the distal portion,, and proximal portion,, together characterized in that: one of the proximal portion and the distal portion includes an axially aligned rib, and the other of the proximal portion and the distal portion including an axially aligned channel sized to receive the rib when the proximal and distal portions are connected together; and the connection protrusion of the at least one valve retention member extends at least partially through a thickness of the valve member. one of the proximal portion and the distal portion includes an axially aligned rib, and the other of the proximal portion and the distal portion including an axially aligned channel sized to receive the rib when the proximal and distal portions are connected together; and the connection protrusion of the at least one valve retention member extends at least partially through a thickness of the valve member.