Disconnecting union on a 2"" water line that was connected to a 4"" water line that was being supported by the 2""line. When the 2""line came apart,the pipe dropped causing the pipe hangers on the 4""line to break allowing the line to come down and rest on top of employees head. during a follow up visit on 2/10/06, it was determined by the dr that dr therapy was needed at this time.