Which joint type is flexible and connects a sprinkler head to a pipe?

The correct choice is the swing joint because it is specifically designed to allow flexibility and movement, which is essential in connecting a sprinkler head to a pipe. This type of joint compensates for any misalignments or shifts in the sprinkler system that may occur due to ground settling or pressure variations. It enables the sprinkler to pivot slightly while still maintaining a watertight seal, effectively preventing breakage or damage at the connection point.

In irrigation systems, having that level of flexibility is crucial to ensuring that the sprinkler head can adjust as necessary for optimal coverage and performance, without the risk of leakage or failure at the connection. This characteristic makes swing joints particularly advantageous in applications involving a lot of movement or terrain that isn't perfectly level, hence their widespread use in irrigation setups.