This information came to me completely by coincidence. I have a user who has been having lots of issues with drawings opening very slowly when they have pipe network data references in them. We've tried several options on how to resolve this with no luck. It was slowing down production really bad. It just so happened that this user, who happens to be one of the best Civil 3D minds I know, was invited to sit at a "round table" discussion among other great Civil 3D minds. In the discussion this exact topic came up and one user in another city, another state had figured out the fix.
This fix is not documented anywhere (at least to my knowledge) and was not provided to us by Autodesk. It has only been tested on a few computers with no known issues, so I can't promise that it will not affect anything else within software negatively, but the few people who are currently using the fix have not reported any issues thus far.
The issue - After installing installing Civil 3D 2014, Service Pack 1 you begin to experience slowness when opening drawings that contain pipe networks or references (data shortcuts) to pipe networks.
The resolution - it turns out that the service pack overwrote two files that somehow are the root of the issue. Replace the following two files with the original ones that shipped with the Civil 3D media:
• C:Program FilesAutodeskAutodesk AutoCAD Civil 3D 2014AeccNetwork.dbx
• C:Program FilesAutodeskAutodesk AutoCAD Civil 3D 2014AeccUiNetwork.arx