Jerry, my house is three years old. About a year ago I would hear my pipes "banging" when I turned on the hot water in my shower and one lav in the master bath. I looked through every reply for every month on this board. I tried every suggestion to no avail. I finally went into the basement and traced the hot water line. The hangers that the plumbers used to secure the hot water lines to the floor joists had worked loose. I put insulation between the pipe and the joists and tightened the hangers. That's all it was, just a couple of loose pipes rattling. I can't believe that most simple suggestion hasn't been posted here! Good luck !
: Jerry:--Could be something as simple as a floating washer in the shower valve; that would be a good place to start....Akmed..