Courtesy Rheem
This Rheem Marathon 40-gallon electric water heater’s tank is made with cross-fiber polybutene that is impervious to rust and corrosion. Because of this, it requires no sacrificial anode rod and carries a limited lifetime warranty against leakage. It has an EF of 0.95, meaning that it has standby losses (heat transfer through the tank walls) of 5% or less per 24-hour period.