Water Supplies (hydrants or draft sites) are "attached" to Structures or Preplans, and can be "removed" or "detached" as well.

You can also permanently DELETE a Water Supply -- maybe you added two of the same water supplies? Deleting a water supply cannot be undone, naturally. So be sure you never want to see the water supply again.

Delete is only available when you are viewing the detail page for the water supply:
​