I'm not a pro so there are things I am not aware of. That said, the topic of thermal expansion comes up frequently on this forum. The only way I am familiar with is the thermal expansion tank as pictured in the previous post. These are used when the home has a closed system. A closed system is created when either a pressure regulator valve is installed or a meter with a check valve such as you describe. What happens is as we all know when water heats, it expands. If the system is open, the expansion is absorbed by the city water main. However, when the system is closed, there is no place for the expansion to go, so it will trip the T/P valve on the water heater. The thermal expansion tank is installed in the cold water intake between the PRV or check valve and the water heater. It is air charged to equal the house water pressure and will absorb this expansion. It is really a small volume of water that has to be absorbed, but with the tank, pressure in the water heater will rise rapidly and will exceed the 150 psi that the T/P is designed for. Installation is quite simple, it requires a tee in the cold water line to which the screw adapter is soldered. The tank screws on to the adapter. The tank does have to be very well supported. Tanks cost around $50 and come in at least 2 sizes to best fit the home. You will have to do this if the meter change is made while you are in the home, the T/P will immediately trip once the system is closed and the heater turns on.
