Which type of fastener is most likely to be rendered useless by the pipe rerouting?

Pre-installed anchors are most likely to be rendered useless by pipe rerouting because they are typically set in place during the initial installation process of the piping system. When pipes are rerouted, the locations of these anchors may no longer correspond with the new alignment of the pipes, making them ineffective for their intended purpose.

When the routing of the piping changes, any pre-installed anchors that are physically anchored to a structure at a fixed point may not provide the necessary support required for the relocated piping. They are designed to hold pipes securely in place based on specific, initial configurations, and changes to the layout eliminate their utility.

In contrast, other fasteners like U-bolts, which are clamped around the pipes, can often be adjusted or relocated to accommodate new placements. Post-installed anchors might also have more flexibility since they can be installed after the pipe has been positioned. Undercut anchors depend on a different mechanism that may allow for minor adjustments, but pre-installed anchors do not have this adaptability. This rigidity in placement underscores why the pre-installed anchors would be rendered ineffective when rerouting pipes.