If you are using the OpenRoads Survey tools in Power GEOPAK, you can use the VBA "LinearFeatureDescription" to automatically annotate the pipe sizes. To do this, the pipe size would have to be imported as a description for the linear feature:
Then you can set up the VBA Macro to annotate the linear feature description:
For an example of setting up Survey to use the VBA Macro, check out this video: 