Is it necessary to install a pressure gauge and a pressure reducing valve with by-pass in a standard installation of a thermal expansion tank

is it neccesary to install a pressure gauge and a pressure reducing valve with by-pass in a standard installation of a thermal expansion tank A pressure gage's always handy to test house pressure.
If the tank's installed on the cold water inlet of a water heater the answer's
No! The PRV valve's installed to reduce excessive water main pressure to acceptable house limits and a by-pass on a expansion tank would defeat its purpose. Regards, Tom

You should have PRV if your incoming house pressure exceeds 75psi. Thermal expansion tank is there to absorb - you guessed it: Thermal Expension. Therefore, it rather deals with high water temperature in your plumbing system.

I have to ask same question as Tom in his previous answer: Why bypassing thermal expansion tank ?

Just to make sure, you are talking about domestic water yes? Not a boiler system. Does your domestic water have a backflow preventer. This would be the only reason you need an expansion tank. Are you replacing an existing tank, or adding one to the system? If you could give us a little more info about your setup, we will try our best to help you do this correctly.

I agree with both answers above.