Only Marathon (by Rheem) offers the one thing you're looking for in a water heater. KEM Electric carries the 50-gallon and 105-gallon Marathon water heater, which is the best water heater available. It features an all polybutene tank that is guaranteed not to leak, rust or corrode for as long as you own your home. It also is one of the most efficient water heaters on the market. To save money off the purchase price and receive a lower energy rate, KEM members can place the Marathon water heater on one of our load management programs.