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Marathon Water Heaters Review And Buying Tips

Note: This post may contain affiliate links. This means that at no cost to you, we may receive a small commission for made purchases.

The Marathon electric water heaters are heating appliances that are cutting-edge but easy to use.

They come with three excellent qualities, including a lifetime warranty, efficient performance, and simple installation.

The company that manufactures these electric water heaters says that they’re “the most durable water heater ever created.

” If you are thinking about buying one of these products but aren’t sure if they are right for you, then you have come to the right place. 

In this article, we will cover all of the features of the Marathon Water heaters, as well as cover some of the many models that you can buy. Keep reading to see if these are the right products for you!

Advantages And Features

The water storage tanks of these water heaters are covered by a lifetime warranty, which is one of the primary benefits, if not the best feature. 

There is guaranteed to be no tank leaks for as long as you own this device, and there is no need to replace the heater every six to ten years due to corrosion as this doesn’t happen.

You will save more money and produce less waste with such an ingenious design.

The Marathon is distinguished from conventional water warmers by its water holding tank.

The PermaGuard seamless blow-molded polybutene eliminates the need for the anode rod, which is a corrosion-prevention component.

The removal of the anode rod eliminates odorous water and rotten egg aromas and reduces maintenance requirements. 

In addition, this material ensures a lightweight construction, which makes installation inexpensive, straightforward, and secure.

The bulk of today’s electric water heaters are constructed of steel and covered with porcelain enamel and an anode rod, leaving them susceptible to water’s corrosive effects.

Marathon Water Heaters Review and Buying Tips

Therefore, electric water heaters from Marathon are a reasonable investment as this will not be an issue for you. 

Here are a few more of the key features of the Marathon water heaters. 

Very Efficient Due To Thick Insulation

The Marathon heating tanks are insulated with R-20 rated, 2.5″ thick Envirofoam insulation.

The 4′ pipe insulation is included in the package, which, along with the high-quality tank insulation, increases energy efficiency and reduces energy loss. 

The maker of the Marathon says that the water tank wall loses only 5 degrees Fahrenheit each day due to the tank’s superior insulation construction.

The Marathon models have a high energy factor ranging between 0.90 and 0.94. (exclusive to 30, 40, and 50-gallon versions).

Very Durable

The outside strong molded tank of Marathon water heaters is built of polyethylene with numerous layers of filament-wound fiberglass to boost the unit’s durability, allowing it to tolerate more hot water pressure than normal heaters while remaining resistant to dents and scratches.

Professional Quality Dip Tube

The distinctive shape of a commercial-grade dip tube (see also ‘Water Heater Dip Tube Explained‘) provides turbulence in the entering cold water and at the bottom of the tank to prevent silt accumulation.

The tank’s bowl-shaped base facilitates simpler drainage and removal of sediments.

Exceptional Heating Elements

The standard water heaters use two heating elements that are made out of stainless steel  with low-watt density coatings for enhanced performance, durability, and energy economy.

The thermally fused top element prevents “dry fires,” while the Incoloy stainless steel lower element prevents lime buildup.

Maximum heating power on 240 V heating elements is 4500 kW, while minimum heating power on 120 V elements is 2000 kW.


Rheem Marathon water heaters are built primarily for use in residential applications such as whole-house and point-of-use heating, however, certain models are also suitable for use in light commercial settings.

These water heaters are available in a variety of sizes and outputs to accommodate a wide range of needs.

Marathon Water Heaters Review and Buying Tips

The Marathon brand comes in a wide variety of various electric heaters.

These types range from the smallest, which is the 15-gallon point-of-use unit known as the MR15120, to the largest, which is the MR105245. 

The most recent iteration is a thermal storage tank that has a capacity of 105 gallons and was intended primarily for use in alternative means of heating water, such as solar, geothermal, or indirect heating.

The tank was designed exclusively for use in these kinds of heating systems.

Standard sizes of forty, fifty, and eighty-five gallons are suited for families with fewer members, and this model is recommended for homes that can accommodate up to seven people.

The MR50245 is a tall type with a capacity of 50 gallons and is around 62 inches in height.

It is the “standard” model that is the most sought after by Marathon customers. 

You may also get it in a smaller “short” version, which has a height of around 43 inches, is 5 inches wider, weighs 5 pounds less, and has the same recovery but a lower first-hour rating. The short version is also available.

Here are a few of the most popular models. 


Because of its space-efficient and compact point-of-use (POU) design, Marathon point-of-use water heaters are an excellent choice for installation in constrained spaces.

POU heaters have the same high-quality characteristics as bigger heaters, but because of their diminutive size and capacity, they are suited for applications that include point-of-service delivery. 

Under the sink, toilets, apartments, condominiums, campers, and restrooms in offices are the most common locations for their installation.

There is a vast range of sizes and capacities to choose from when shopping for a POU heater.

The assortment of point-of-use devices may be purchased in either a 15- or 20-gallon capacity, depending on the user’s specific needs.

In residential applications, the warranty on tanks is for life, while the guarantee on other components is for six years. 

If, however, the system is used for light-duty commercial applications, the warranty on tanks is increased to ten years, while the warranty on other parts is reduced to just one year. 


Marathon Water Heaters Review and Buying Tips

Heavy-duty electric water heaters produced by Marathon are designed for installation in challenging environments and high-temperature applications.

This is because they can heat water to temperatures as high as 175 degrees Fahrenheit, which is the maximum temperature they are capable of reaching.

Heavy-duty models with capacities ranging from 85 to 105 gallons may be found in both the 85-gallon and the 105-gallon sizes.

Both models have a towering height. They are also providing a better design by making use of enhanced titanium sheath components, which are employed in circumstances in which intense water is present.

If you want to use an alternative energy source, such as geothermal or solar water heating, either by itself or along with the built-in hydronic system, then the “Multi-Port” storage tank from Marathon is the product that is best suited to meet your requirements. 

You can use it either by itself or along with the hydronic system.

You have the option of selecting from one of three distinct varieties, with tank sizes typically ranging from fifty to eighty-five to one hundred and five gallons respectively.

The heavy-duty water heaters come equipped with insulation that is exceptionally substantial, which helps to limit heat loss much more than it would otherwise be possible. 

The multi-port look and design takes advantage of both the huge water connections, which are situated in an accessible place in front of the unit, as well as the electric heating components, which are used as a backup heating source.


If you are interested in purchasing an electric water heater from Marathon, your best bet is to go with one of their regular, heavy-duty, or point-of-use models. 

Choosing this brand is a safe bet in any situation. The Rheem Marathon heaters are pretty pricy products, but they have several fantastic features that are not found on typical types.

These features include no tank corrosion, a lifetime warranty, the absence of an anode rod, less involved maintenance, easy draining and sediment removal, increased savings, and decreased pollution.

author avatar
Anthony Barnes
Anthony Barnes is the founder of Water Heater Hub and a second-generation plumber by profession. Before developing Water Heater Hub, Anthony Barnes was a full-time plumber, and he has undertaken a wide variety of projects over the decades. As a second-generation plumber, it was easy for Anthony to get used to the technicalities of all from a tender age


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