What is wrong with my water pipes?
I have an issue with my water pipes that I don't quite understand. It only happens with my shower, and it only happens early in the morning. I turn on the hot and cold water in the shower and turn on the diverter. When the problem happens (not all the time), I hear a loud whining and rattle and I seem to lose a little water pressure. I can usually fix the noise by un-diverting and re-diverting, but the slight drop in water pressure remains and a very faint hum is noticeable. Also, when I un- and re-divert, the water temperature temporarily loses its heat (over maybe 15 seconds).
This only seems to happen when I shower around 7:30-8:00am, and it happens somewhat consistently (maybe 80-90% of 8am showers). It almost never happens, though, if I shower in the afternoon. Those always have top water pressure and no noise. Furthermore, the shower is the only place where there is noise and a drop in water pressure - no other taps do this.
Any ideas on where to start?