2,3 or 5 gallon expansion tank?

[Nate848]

I have a heat pump electric water heater with 65psi and 50 gallon water heater. What size do I need as several people all told me difference sizes?

Thanks

 

[frodo]

I have a heat pump electric water heater with 65psi and 50 gallon water heater. What size do I need as several people all told me difference sizes?

Thanks

 

[breplum]

As I like to say: LMGTFY heard of a search engine?
https://www.amtrol.com/resources-rewards/selection-tools/
Techincally, you only need an expansion tank if you have a closed system. In other words, if you have a city water pressure supply, with even a pressure reducing valve (as long as that PRV has built in bypass) then no expansion tank is required.