For some reason fittings were removed from the Stormwater Data Model at version 4. They were under Stormwater Junctions. Clean Outs were also removed from Stormwater Junctions but they were added to Stormwater Devices. The current data dictionary for 10.9.1 still does not have any reference to fittings that I can find.
Please add fittings back to the Stormwater Data Model. Maybe it could be similar to how fittings are setup in the Sewer Data Model?