A testable back pressure valve can include a body. The valve can also include a first flow regulating device movably disposed within a top end of the body, where the first flow regulating device is configured to move from a first default position to a first position based on first flow characteristics of a first fluid that flows into a top end of the body toward a bottom end of the body. The valve can further include a second flow regulating device movably disposed within the bottom end of the body. The valve can also include a network of channels disposed within the body between the first flow regulating device and the second flow regulating device.