With all of the other pluming I am doing right now it would be an easy time to add an expansion tank. The question is do I need one? Should I add one just because? I got a new water meter a few months ago and I have a 40 gallon gas HWH that is about 2 years old. The city is doing lots of work on the water plant and water lines in the streets. I could also add a permanent pressure gage. Any thoughts on this?