Since 2013 is the first version to have pressure networks, do I need to explode the objects before saving to a previous version? Or is there another method? I will lose all my properties if I explode the objects I believe...
Unfortunately EXPLODE or EXPORTTOAUTOCAD seems to be the only options to get your pressure pipes objects back to earlier versions. Of course this will reduce them to AutoCAD primitive objects, but they should still resemble the original objects.
If you would like to leave feedback about pressure pipes functionality please follow this link: http://usa.autodesk.com/adsk/servlet/index?siteID=
There is no way to save any civil 3d objects back to previous versions. Can't be done. Civil 3D is not backwards compatible. If you need the data in a previous version, you have to convert it to AutoCAD entities (as Seth says) or export to LandXML and then import that back into the previous version. However, since previous versions didn't have pressure networks, you can't import them into the previous versions.
In other words, if you want to use pressure network tools, you have to use Civil 3D 2013 (at least until the next version comes out then you could probably use that as well).