Water heater expansion tanks were introduced in the late 1950s. Before that, residential water heaters were designed as “closed systems,” where water was stored in a single tank without any way of accommodating the thermal expansion of the water in it. This expansion can lead to pressure bui...
Install the expansion tank on the cold water supply line to the water heater at a point between the water heater and backflow preventer or other one-way device (see Amtrol's instructions Figure 2.) Mount [hot water thermal expansion] tank vertically only Once the expansion tank is installed,...