In ArcGIS (ArcCatalog or ArcMap), there is no ability to undo your changes after they have been made. Skelebrator makes transactions against the GEMS database without the ability to rollback those changes. From within WaterGEMS , changes can be undone on a global level by not saving the model after skeletonizing. However, any changes made prior to skelebration will also be lost if this method of avoiding committing skeletonization changes is used.

Making a copy of your model up front will ensure that you can always get back to your original model if problems occur.