My problem started a few months ago. I started to notice my cold water pressure was spiking to over 140 and broke one of my Whole home water filter tanks.
I had the pressure-reducing valve replaced thinking that was the problem. Then I continued to notice it happening, so I tried shutting off the supply to the hot water heater at night and would check the pressure in the morning and it was fine. I did this for several nights and every night it was fine, so obviously the pressure increase is migrating back out of the hot water heater into the cold water supplying it.
Why does this happen and how the heck do I fix it?