Originally Posted by YoungRascal
Any ideas on how I can fix this or to further troubleshoot it?
Was there water pressure issues before you attempted to flush your tank?
Was the shower/tub you used to measure the hot/cold flow a single handle or two handle system?
Does the faucet in the bathroom with the low pressure shower show signs of low pressure as well? If you leave it off for a minute then turn it on, does it blast normal pressure before quickly dropping off? If so, does it do it on just hot? or both hot and cold?
Because of the pressure drop at the tank drain, I'm inclined to suggest the issue is before the tank, perhaps the gate valve. But if you are having a 50% pressure drop on a cold water hosebib when the hot water is turned on, then it suggests it's probably debris clogged in the PRV, or the PRV is shot (unlikely given it's age, but possible).