Water Heaters - Thermal Expansion Tank

I installed a Watts thermal expansion tank on my closed system. The pressure was running 150-160 psi. My incoming water has a pressure reducer taking it from 180 to 60 psi. I pumped up the tank to match the incoming 60 psi.
I placed a pressure gauge on the drain of the hot water tank last night. This morning, it had reached 160 again.

I am clueless as to what is wrong. Any advice?
Thanks,

An expansion tank will absorb a short-term expansion caused by the heating of the water in the tank. Once the burner turns off, that excess pressure is also released back into the system by cooling of the pipes, and of course as soon as any tap is operated, the system equalizes also.

An expansion tank cannot absort a permanent increase in supply pressure. Your symptoms are classic for a pressure regulator with a bad seat or pinhole in the diaphragm. During periods of no water use, the house side gradually creeps up to street pressure, and an expansion tank cannot absorb this. Does your pressure return immediately to ~60 when any tap is opened briefly? That would confirm this situation.

Yep, that is exactly what happens. It returns to ~60psi. If I were to turn off the hot water heater that would eliminate the expansion factor and tag the pressure regulator as the culprit?
Thanks,

Monte

That would be it. I guess the same situation applies once when I thought it was a non functional Mercedes Benz Expansion Tank, but, upon reading this http://www.eurobzparts.com/mercedes-benz-expansion-tank/ , it has nothing to do with the problem. It’s just that the pressure regulator fails.