OK update:
My wife called 2 plumbers today and they came out. Here's what she said they said:
- Water pressure too high, need to replace the (either the man valve or pressure regulator, my wife wasn't clear). Both said it's common to our area. Both took pressure readings and said it was 90-100 psi, "way too high". One gave a quote of $465 the other aboutg $250 to replace the valve/pressure regulator.
Well, here's what I know: I just took a pressure reading with my guage and it's reading just under 80 psi, the same as it did when I bought the house 10 years ago and checked again after replacing a water heater about 4 years ago.
The high frequency water hammer effect only affects this one shower stall, none of the other showers or faucets, most of which are designed just like this one.
I installed a water expansion tank, about 1.5 cu ft. 4 years ago; I filled it with 80 psi air then. it now reads 70 psi; I guess I'll uninstall it, take it down to the garage, fill it back up and reinstall it and see if that makes any difference.
Any other ideas or comments? Anybody believe the plumbers?
Thanks,
Merlin