I am experiencing low water pressure in one shower on the second story in my condo. The water heater is on the first floor. The shower downstairs has good water pressure. Every sink and toilet seem to have good water pressure too. Neither shower has a bathtub faucet. Both faucets are single handle.
I have tried the following:
1) Removed the shower head from both showers. Water pressure is significantly lower coming out of the pipe upstairs than it is downstairs.
2) Switched the cartridges between the showers. Performance for both showers did not change.
I have limited access to the rough-in valve, but can't access any of the pipes unless I remove drywall.
Additionally I have noticed that there is intermittent vibration in the pipe when turning the faucet from cold to hot. The handle starts pointed downward, and the vibration starts when the handle is about 90 degrees counter clockwise. The vibration stops if I continue to turn it all the way to 180 degrees, and turn it slightly harder at the end.
I'm not sure if these two problems are related or not.
Any ideas on what may be occurring here?