I have a 40 gal natural gas water heater that's at least 17 years old and so is past its prime, but still heats up the water just fine and quite quickly, so there are no performance issues with it.
However, I've noted that over the past few years that whenever it fires to heat the water back up after hot water is drawn off for use that the water pressure in the house goes up significantly. I do have a one-way pressure reducer valve at the water service entrance that does not permit any back flow which was installed a few years ago, but the timing does not seem to correlate with the start of the increase in pressure after using hot water.
I do not have any expansion tank installed, but I know that when I originally moved into this house that this pressure increase was not present, so that's not the core issue.
Once I draw off some water from the pipes (a cup or two or water will bring the pressure back to normal) the pressure remains where it should. Is this increased pressure when water's been heated a sign that the heater's ready for replacement, or is the root issue somewhere else?
Thanks!