Water Pressure Loss after Water Heater Replacement

Yesterday I replaced my water heater. I also replaced the shut off valve to the water heater because that had started to leak. We noticed a drop in water pressure in the house, the hot water in particular. I have done a little research and l guess it could be the pressure relief valve going bad. But it seems coincidental that that would go bad now. Since we had to replace the shut off valve, we had to shut off the main. Would that have disrupted the prv, causing it to go bad? Or could it be the water main valve itself since it has only been turned a handle full of time since 1986?

Most likely cause is crud flushed down the line downstream of the tank. Take off your faucet aerators and turn the hot water on high and flush the pipes out. Clean out the aerators.

Otherwise you may have a flake of rust wedged in a pipe somewhere, which will require a pro to diagnose/ repair.

If the main shutoff was a gate valve, it may not have fully opened. When old, the gate tends to break off from the spindle that pushes or pulls it into place. This would require replacing the main shutoff, which can be a pain since you have to get the water company involved to shut off the water at the road. Crud caught in strainers at your fixtures could also be clogged up by the debris dislodged by turning water off and on at the main. If you have the heat traps at the WH installed backwards, your hot flow will decrease radically, but it would not affect the cold. Pick up a water pressure gauge for about $10, screw it onto say a hose bib, or the drain on the WH, or with adapters, nearly anywhere. This will tell you if your PRV is messed up. They often fail by not reducing the pressure, not having it too low, unless the inlet screen filter is clogged. Clogging this filter would reduce volume, but static pressure would likely be okay when no flow is occuring.

Thanks for the responses. I will check to see if there is any crud trapped in any aerators but I noticed the pressure loss at the bath tub as well which does not have aerators. Also I do not have heat traps installed on the water heater.

If I get a water pressure gage, what kind of pressure am I looking for that would tell me if the PRV is bad?