An assembly of screens made of connected joints with exterior bypasses that span the threaded connections among the joints features common fluid connections for the bypasses adjacent joint threaded ends that are connected with a coupling. A mandrel spans from one joint to the next inside the threaded coupling and is sealed to the respective bases pipes on opposed ends of the coupling. At each end of the mandrel the surrounding base pipe has openings from the common fluid connection where the bypasses terminate to define an annular flow path between pairs of common fluid connections. The bypasses can have slanted gravel outlet passages or no gravel openings at all. The bypasses can span over screen or blank pipe with an option to mount a shroud over the generally parallel bypasses.