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Marathon 75 Gallon Heavy Duty Water Heater


Quick Overview

MHD75245 Electric Water Heater
SKU: MHD75245


The MHD75245 Rheem Marathon water heater with a tank capacity of 75 gallons is a good choice for installations in homes with 3+ bathrooms or more than 4 family members. The MHD75245 Marathon water heater can deliver on average 78 gallons of hot water per hour (first hour rating).

Marathon water heaters are considered to be the best electric water heaters on the market. Marathon heaters carry a limited lifetime warranty against water heater leaks. All Rheem Marathon water heaters have a high efficiency design with a lightweight tank that cannot rust through or corrode. Marathon heaters are stronger and higher quality by virtue of being built without using steel or other metals. Rheem Marathon water heaters are made of cross-fiber polybutene. This material is ten times stronger than steel. Cold water heavily infused with minerals cannot damage this water heater tank’s strength. As a result Marathon water heaters last much longer than electric water heaters made of steel.

Marathon water heaters are built with one fused upper heating element made of copper to help protect against dry firing. The Marathon 75 gallon electric water heater’s lower heating element is made of titanium to provide resistance against lime and sediment build up. While slightly smaller, the MHD75245 Marathon water heaters can make a good replacement for standard 80 gallon electric water heaters.


  • Seamless, blow-molded, polybutene tank impervious to rust and corrosion.
  • Multiple layers of filament wound fiberglass to give tank extra strength.
  • A recessed drain valve so it's out of the way of brooms and scrubbers.
  • Tough molded polyethylene outer shell to resist against dents and scratches.
  • High temperature polysulfone dip tube.
  • Factory installed conduit between element control boxes.
  • All plastic tank eliminating the need for an anode rod.

Energy Savings

The 75 gallon Heavy Duty Rheem Marathon water heater  is unrivaled in its energy savings. All Rheem Marathon water heaters use electric immersion water heater elements which transfer 100% of their energy into heating the water. Rheem Marathon water heaters significantly reduce heat losses by insulating the water heater tank with Polyurethane Envirofoam. The use of Envirofoam traps the heat inside the tank and keeps the water hotter for longer periods of time without the elements cycling on and off to re-heat the water.

Standard electric water heaters suffer from high standby losses; up to 20% of the energy used in old standard electric water heaters is to compensate for heat loss. This is not the case for Rheem Marathon water heaters due to the Envirofoam insulated tank. Replacing a standard electric water heater with a Rheem Marathon water heater can result in significant savings on the home owner’s electric utility bills over the course of a year.


Capacity: 75 Gallons
Element Size: 4500 Watts (240 Volts)
Tank Height to Water Connection: 62 and 5/8 Inches
Tank Diameter: 28 1/4 Inches
Weight: 112 lbs
Standards: Meets or exceeds ANSI standard and is UL listed. 
Energy Factor:

All Marathon water heaters 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.

This 75 gallon marathon electric water heater should be taken into consideration for replacing standard 80 gallon water heaters.


Rheem Marathon water heaters come with a residential limited lifetime tank warranty as long as you own your home. If the home is sold, the warranty transfers to 15 years from the date of installation and the next owner receives coverage for the time remaining. All elements and parts are warranted for 6 years from manufacture date against factory defects.

Additional Information

Manufacturer Rheem
Energy Source Electric
Tank Size (gal) 75
Certifications None
First Hour Rating 70 - 79