Today we will talk a little about expansion tanks. What is it? A very basic explanation would be that it is a type of overflow for your water heater. Heat makes things expand, therefore your water heater makes water expand. When there is no where else for the water to go, the expansion tank is there. Why do you need one? It helps minimize any damage to your plumbing in general. Do I have to have one? It is, by code, required to install an expansion tank. Customers may choose to not have one installed, but the manufacturer warranty of the water heater and the plumbers warranty may be void. Be sure you know the facts about it first before you decide not to have one installed. Below is a small diagram of what the thermal expansion tank does, and why it is needed as a part of your plumbing system. Please post any questions below. Thank you!