We do recommend a thermal expansion tank for those who want to extend the
life of their new water heater(s). In the future, we expect expansion
tanks will be required by city code. Expansion tanks are a small additional
cost that will save the homeowner money in the long run. The expansion
tank helps reduce stress on valve stems, safety valves and ball seals,
and it is a pressure safety component.
As of April 16, 2015, new energy efficiency regulations have been put in
place by the Federal government, which have resulted in a 20-30% increase
in water heater prices. Warehouse supplies of older water heater units
were expected to be depleted an estimated three months after the regulatory date.
Third party YouTube video that explains the importance of a thermal expansion tank.