When you select the "Empty Pipe" tool and set the priority to something other than 5 (I usually go 7-9), the selected sub-priority level is not set to the placed tasks.
Steps to Reproduce
When there is a filled pipe, switch to the "Empty Pipes" tool, then select a sub-priority other than 5. Then and you place "Empty Pipe" tasks on the pipes. Then switch to the priorities view, and see that the placed tasks have priority 5.
This issue has not been confirmed by a developer yet.