I have posted previously on my son's house he just bought which had the hot/cold reversed on the hot water heater, no pressure reducing valve, and an expansion tank that had failed. We replaced the TP valve on the water heater over Christmas because it was dripping. His house pressure was at 90 PSI.
Well, his hot water heater failed this week, brown water that never cleared even after flushing. So, he had a local plumbing company come in and replace the water heater, add a pressure reducing valve, and replace the expansion tank.
The outcome was that the water heater drip tube had not been switched so the hot and cold reversed was bad. The anode rod was just a wire so completely depleted. The expansion tank was on the hot side. The plumber fix both of these problems. My son ask about setting the expansion tank pressure equal to the house pressure and the plumber basically said it was pre-charged and fine. The plumber set the PRV to 70 PSI. This weekend my son set the PRV to 60 PSI and set the expansion tank to 60 PSI also, it was preset to 40 PSI.
So, my question to all plumbers why do you not offer a yearly test of your expansion tank and PRV? I always get brochures in the mail about a yearly checkup for my heating/cooling system. But, in my area nothing on the plumbing side. It would seem if folks would do this alot of expansion tanks and PRV valves would be fixed.