Select
the piping segment to mirror.
Click the 
toolbar icon. The cursor changes to indicate mirror mode.
Select a node that defines the mirror
plane. The segment mirrors relative to this plane.
The Mirror dialog appears:
Select the mirror plane. Choose from global coordinate planes or local pipe planes.
Check "Copy selected piping" to create a mirrored copy of the segment. Leave unchecked to mirror the original segment.
Click Apply then OK. The program prompts to insert a tee at the branch node.
The mirror operation includes these elements:
Pipe uniform loads
Nodal concentrated forces
Custom restraint definitions
Custom expansion joint restraints
Nodal deformations
Restraint displacements
Tools > Mirror