Marathon Water Heater Age Lookup

Marathon is Rheem's answer to the way water heaters usually die. Instead of glass lined steel, the tank is seamless blow molded polybutene, which cannot rust, corrode, or scale. There is no sacrificial anode rod to replace because there is no steel to protect, and the tank carries a lifetime residential warranty, the only one of its kind in the industry.

The line is electric only, in 30, 50, 85, and 105 gallon sizes, covering household and light commercial use. Thick foam insulation keeps standby loss low. Elements and thermostats are ordinary replaceable parts, which changes the repair calculation on an old unit: when an element fails on a twenty year old Marathon, replacing a part on a tank still under warranty usually beats replacing the heater. Marathon is sold through Rheem contractors rather than retail.

The serial opens with a four digit month and year code, so a serial beginning 0189 is January 1989. Units from before the mid 1990s used a different scheme, a single letter followed by the two digit year and then a dash and a sequence, which gives the year but not the month. A year only answer on an early Marathon is the correct answer, not a failed decode.