When you are in the market for a new water heater you also need to consider a thermal expansion tank. An expansion tank is required in many cities in the KC area, including Shawnee, Overland Park, Lenexa, Leawood, Olathe, and Kansas City Missouri. The expansion tank is only required in homes and businesses that have a closed loop systems. A closed loop system is usually created by a backflow device in commercial applications and a pressure reducing valve in residential applications.One of the biggest topics for water heaters are the new energy efficiency requirements that will go into effect in 2015. The energy factor for water heaters was raised in 2004 to be a minimum of .59 EF on all tanks.