Marathon Water Heater

The Rheem Marathon water heater is the most durable water heater on the market. 

Price:From: $935.38

SKU: N/A Categories: ,


The Rheem Marathon water heater is the most durable water heater on the market. The lifetime tank warranty makes purchasing easy. The Marathon water heater is easy to install and lightweight making installation and maintenance quick and cheap. Over the course of a year Marathon water heaters can account for significant savings on a homeowner’s electric bills. The water heater contains a plastic inner tank preventing rust and corrosion. It is insulated with 2.5″ of polyurethane to reduce heat loss and save energy. The tank is then sealed in layers of wound fiberglass, giving it outstanding strength. Built in protection ensures that elements are only turned on when submerged in water. Every Marathon water heater uses electric immersion water heater elements which transfer 100% of their energy into heat. Standard electric hot water heaters suffer from high standby losses. Water temperatures in old electric water heaters can drop by up to 30 degrees if the water heater was not used for a 24 hours period. This is not true for Rheem Marathon water heaters, making them the best on the market.

  • All units come complete with factory installed temperature and pressure relief valve, replaceable brass drain valve, and vacuum relief valve. The connections for cold inlet and hot outlet are 3/4 inch NTP, and should be roughed in at 5 3/4 inches on center.


Rheem Marathon water heaters (MR and MTS models) used in single family dwellings come with a lifetime tank warranty as long as you own your home. If the home is sold, the warranty transfers to a 10 year warranty from the date of the original installation. The next owner receives warranty coverage for the time remaining. All elements and parts are warranted for 6 years from manufacturing date against factory defects. Units must be registered within 90 days of installation to qualify for Rheem’s Limited Lifetime Warranty. 

If you have questions about shipping, find our policy here.

Specifications 15 Gallon 20 Gallon (2000W) 20 Gallon (3000W) 30 Gallon 40 Gallon 50 Gallon 50 Gallon (Low Profile)
Capacity: 15 Gallons 20 Gallons 20 Gallons 30 Gallons 40 gallons 50 Gal 50 Gallons
Element Size: 2000 Watts 2000 Watts 3000 Watts 4500 Watts 4500 Watts 4500 Watts 4500 Watts
Tank Height: 31.75″ 30.5″ 30.5″ 49.5″ 65.5″ 66.75″ 47.25″
Tank Diameter: 19.56″ 23.5″ 23.5″ 21.75″ 21.75″ 23.5″ 28.25″
Weight: 58 lbs 61 lbs 61 lbs 75 lbs 90 lbs 100 lbs 100 lbs
First Hour Rating: <50 Gallons <50 Gallons <50 Gallons <50 Gallons 50-59 Gallons 61 Gallons 61 Gallons

Additional information

Weight Select options for details
Dimensions Select options for details

15 Gallon, 20 Gallon (2000W), 20 Gallon (3000W), 30 Gallon, 40 Gallon




15-20 Gal Spec Sheet
30-50 Gal Spec Sheet

You may also like…