What is an expansion tank and what would this have to do with the water pressure regulator valve?
Answer Connie, An expansion tank is designed to prevent thermal expansion in a piping system. Here is a link that explains what it is: http://www.watts.com/pro/divisions/watersafety_flowcontrol/learnabout/learnabout… It is helpful to have one for each individual water heater, but, not necessary if you aren’t having problems with your system now. The pressure regulator will reduce the pressure only, the expansion tank helps check excessive water temperature. Hope this helps.
