You can use the Rotate grip 
to rotate plumbing in-line parts, fittings, and takeoffs 180 or 90 degrees in the direction indicated by the grip.
Rotating a 3-way valve 90 degrees in plan view
AutoCAD MEP 2023 toolset displays Rotate grips on the plumbing line in-line parts, fittings, and takeoffs with connectors on opposite ends. However, when necessary to preserve the connectivity of plumbing runs, the software limits the available rotation options or hides the grips.
When you rotate a part, fitting, or takeoff that is connected to other objects, the software adjusts the connected objects to maintain their connectivity. For example, the software might make minor adjustments to the lengths of connected plumbing line segments after you have flipped a fitting. If it cannot adjust the objects, it disconnects them.
The rotate grip turns a part 180 degrees. The flip grip orients a part (in-line or anchored MvParts, fittings, or takeoffs) for flow direction.
