How can I stop my handheld shower head from leaking?
I found the problem. Debris from a ruptured water filter (for the entire house) had come through the pipe and partially blocked a small filter between the pipe and the plastic T that holds the pivot ball. When I completely remove the shower head (so that I just had a pipe coming out of the wall in the shower), I could see a small screen filter in the plastic T of the shower head, and it had some junk partially blocking it. When I remove that and re-attached the shower head, the problem went away.