no hot water presuure

i just replaced my water heater and still have no hot water pressure...unit replaced was 11 yrs. old and both elements were out. i've had very little hot water pressure for some time now, all faucets in house have been replaced in the last year. i had previously flushed heater, but only had crystal clear discharge from drain. water supply is very high in calcium deposits and i have cleaned shower head and removed aero's. hot water discharge supply lines are all 3/4" copper...cold water has good pressure throughout house. when hot water faucets are first turned on i have good pressure for a minute and then quickly die to just a trickle and to nothing if another faucet is opened. i "flushed" each hot water line with air (90psi) prior to connected water supply line. (there are no plumbing leaks)

Greetings Dean welcome to the Forum.

Sure sounds like it's in the CW supply line to the Heater.

Valve not opened fully, some restricton there, maybe even before the Valve.

Have a good Day !
S.W.

that's what i thought, even started to go ahead and replace when i did heater, but then figured it might be heater itself restricting flow. you know what they say about hindsight being 20/20 ! thanks for the input i'll let you know if it works