Marathon Water Heaters
Review and Buying Tips

Marathon water heaters are unique but very simple electric heating appliances with the three great features; lifetime warranty, high efficient operation, and easy installation. According to Rheem manufacturer, Marathon is "the most durable electric water heater ever made". Check out the features and benefits that are making it one of the preferable products for heating potable water in residential homes.

Features and advantages of Marathon water heaters

Marathon water heaterMarathon water heater

One of the main advantages, or if I can say the best features we can see on the Rheem Marathon electric water heaters is Marathon's lifetime warranty on the water storage tanks.

Lifetime warranty means no tank leaking for as long as you own this unit - no need to buy a heater every 6-10 years, due to the corrosion problems. With such a unique design, more savings for you and less garbage into the landfills.

The water storage tank is what makes Marathon water heater different from others. It is made of the seamless blow-molded polybutene patented as the PermaGuard, and such a tank design eliminates the need for the anode rod, a component part used for corrosion protection. With the absence of the anode rod, smelly water problem, or rotten egg smell is eliminated and there is less maintenance involved. Also, such a material ensures lightweight construction and that means inexpensive, easy and safe installation.

Most of the electric water heaters today, either coming from AO Smith, Bradford White, Kenmore, GE, Rheem and other, are made of steel and protected by the porcelain enamel and anode rod... still fully unprotected from the corrosive water action.

This is why Marathon electric water heaters are a good buy.

Thick insulation for the high-efficient operation

Marathon heater tank is insulated with the 2.5" thick Envirofoam insulation with the high insulation value of R 20. The 4' pipe insulation is included in the package so together with the good tank insulation provides higher energy efficiency values and reduced energy loss. Due to its superb insulated tank design Marathon manufacturer claims that there is only 5 F of heat loss in 24h through the wall of the water tank.

All of the Marathon models are designed with the high energy factor ranging from 0.90 to 0.94 (found only on 30, 40 and 50-gallon models).

Resistant to stress and impact

Outer tough molded tank on Marathon water heaters is made of the polyethylene with the multiple layers of filament wound fiberglass to increase the durability of the unit so it can withstand higher hot water pressure, when compares to the standard heaters, making it resistant to the dents and scratches.

If you require professional assistance, contact a local water heater expert today!

If you need HELP contact an expert today!

Professional grade dip tube

A dip tube is the commercial-grade with the unique design, to provide the turbulence in the incoming cold water and at the bottom of the tank, in order to reduce the sediment build-up. Bowl shaped bottom of the tank allows easier draining and removal of the deposits.

High performing heating elements

Standard Marathon water heaters are equipped with the two stainless steel heating elements, low watt-density coated elements for greater performance, durability, and efficiency. Thermally fused upper element provides protection against "dry-firing" and stainless steel Incoloy lower element provides protection against the lime build-up.

Maximum heating power is 4500 kW on the heating elements, which uses 240 V, while the minimum is 2000 kW found on elements using 120 V.


Rheem Marathon water heaters are mainly built for the whole house and point of use residential applications, while some can be used in light commercial applications.

There are several types of Marathon electric models to buy, which are different in the capacity and size; from the smallest MR15120 as the 15-gallon point of use unit to the largest MR105245. The latest model is a 105-gallon thermal storage tank, designed for alternative water heating applications, such as solar, geothermal or indirect heating.

It is recommended for large homes with up to 7 members, while for smaller families, popular sizes of 40, 50 and 85 gallons can be used.

The most popular "standard" model from Marathon is the 50-gallon model MR50245, tall in size with the height of approximately 62", also available as the short type with the height of approximately 43", which is 5" wider, 5 pounds lighter, has the same recovery but smaller first-hour rating.

Marathon point-of-use models

Marathon point-of-use water heaters are design for space-saving and installation in limited spaces. They utilize the same quality features as the larger heaters, but due to its small size and capacity, they are used for point of service applications and are usually installed under the sink, in lavatories, apartments, condos, camps, and restrooms in offices.

The group of point-of-use models comes in two sizes - 15 and 20-gallon. The warranty in residential applications is also lifetime and 6 years on other parts, and if used for light duty commercial applications, the warranty on tanks changes to 10 years and for other parts only one.

Marathon heavy duty

Marathon heavy-duty electric water heaters are designed for installation in harsh environments and for high-temperature applications as they can heat water up to 175 F.

There are two heavy duty models with the capacities of 85 and 105-gallon, both tall in size. They are also providing a superior design with the upgraded titanium sheath elements, used for the extreme water conditions.

If you are planning to use an alternative energy source, like solar water heating or geothermal, or in combination with the hydronic system than Marathon "Multi-Port" thermal storage tank is an ideal solution for you. You can choose between three models, standard sizes of 50 gallons, 85 and large 105 tank size.

Heavy duty Marathon water heaters are equipped with the thick insulation to reduce the heat loss even more. The multi-port design utilizes the large water connections, conveniently located in front of the unit, and for backup heating, electric heating elements.


Either you are buying a Marathon electric water heater with the standard height, heavy duty or point of use, you will not go wrong with the selection of the brand. Yes, Rheem Marathon is an expensive water heater, but it provides many awesome features which are not found on standard type; no tank corrosion, lifetime warranty, lack of anode rod, less maintenance involved, easy draining and sediment removal, more savings, and less pollution.

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