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Review Rheem Marathon Water Heater


Marathon water heaters at Amazon


Manufactured by WHI Water Heater Innovations
Owned by Rheem
Marathon at Rheem
Marathon use and care guide
Marathon warranty, and claim procedure
2008 Sell Sheet with model numbers
2012 Sell Sheet with model numbers
Rheem Marathon parts list
Rheem marathon parts list 2011/ pdf
Marathon troubleshoot walk-thru/ pdf
Rheem parts warranty claim form

Quick review Marathon non-metallic water heater

Rheem Marathon is ordinary 240Volt residential electric water heater,
except with foam tank instead of metal tank.
The purchase price is 4x ordinary water heater, and Marathon offers few advantage that cannot be achieved with less expensive water heater. Except lifetime tank warranty offered with Marathon, and anode-free tank that does not cause odor.

Marathon will not pay back the purchase price in most instances, but there are benefits for buyers wanting longer tank warranty for home installation, those wanting tank that can be installed in damp environment with possible reduced warranty, those needing lighter-weight tank that can be lifted more easily, and those experiencing chronic odor problems caused by anode rod that is found inside all steel-tank water heaters. Read about anodes


According to mfg, there are no toxic chemicals from using Marathon polybutylene water heaters. However Page 1 of Marathon use and care manual has following warning: 'Calif Proposition 65: This product contains chemicals known to State of California to cause cancer, birth defects.' Manufacturer's stated purpose for disclaimer is avoidance of lawsuit, which means you-the-consumer cannot claim harm since you were warned. On other hand, much information on this page is also from product manual so Rheem is offering transparency.

Is Marathon polybutylene cause for alarm? My opinion:  Probably no cause for alarm. Polybutylene is widely used for household water pipe and other products, for years, both pre and post scientific era. And all household products pose risk, from bug-spray to pills to gasoline.
My friend who owns a Marathon heater remains full of strong-headed opinions, same as before he owned the product. No change observed.
Keep in mind following things
1) You do not drink large amounts of hot water from the water heater tank. Cold water line does not take water from water heater. See image
2) All steel tanks have anode rod. Marathon does not have anode rod. There are health concerns over aluminum anode rods. Read
3) EPA permeation and leaching science 2002  Read pdf   Polybutylene is better than pvc
  Water is universal solvent. Don't drink the water? or beer from a can or bottle? or breathe the air or eat the food? ... especially if you're older than 30 and want to live. 

Advantages and Disadvantages

Rheem Marathon
Advantages for Marathon:
1) Tank will not rust 2) Limited lifetime warranty on tank for single-family residential tank installation, 3) No anode rod: eliminates odors caused by harmless bacteria reacting with anode rod, 4) Lightweight tank is easy to carry, 5) Larger element openings make it easier to remove sediment build-up, 6) Non-metallic water heater can be installed in moist environments such as boat or agricultural installation, with diminished warranty 7) Parts have 6 year warranty, 8) Brass drain valve instead of plastic drain valve, 8) Dip tube stirs sediment off bottom to resist sediment build-up, but this is also available on other brands 9) No need to inspect anode rod once each 2-4 years 10) Thermostats have higher temperature range than typical water heater, which can lead to more hot water. 11) Available in large capacity sizes: Good for homes with oversize bathtub: The 85 gallon and 105 gallon size will work with oversize bathtub. 12) Higher temperatures and pressures are acceptable. Marathon is often used as solar water heater storage tank, since solar temps can reach 180 degrees F, which exceed max 150 degree rating for ordinary steel tanks.

Similarities to other water heaters: 1) Electric water heaters are simple to install and repair. Homeowner repair and installation is generally easy 2) No energy-saving advantage buying Marathon vrs other electric water heater, 3)  Marathon insulation is generally thicker, but .94 EF energy factor and operating cost are same as ordinary electric water heater per gallon of heated water, and has 20 gallon per hour recovery same as other electric water heater, assuming 4500 watt elements 4) Maintenance schedule is same as typical electric water heater, except no anode inspection needed, 5) Installation is same as typical electric water heater, except Marathon is easier to lift 6) Marathon is non-simultaneous so both elements are not ON at same time, so Marathon can replace any ordinary electric water heater without electric wiring change. Use 10 gauge wire with 4500 watt elements 7) All electric water heaters can be re-wired to meet off-peak objectives. Rewiring inside tank can void warranty. Read more about off-peak 8) Adding timer to any electric water heater will not void product warranty

Disadvantages for Marathon: 1) Marathon costs 4x more than ordinary steel-tank heater, and will not pay back in ordinary household circumstance. 2) Marathon TP valve, thermostats, elements and other parts are non-generic and should be ordered in advance to avoid repair delays, How to troubleshoot and fix water heaters 3) Marathon elements burn out more frequently, Parts sheet 4) If home has hard water, Marathon elements should be changed to 3800 watts, which slows heating and recovery  5) Marathon warranty is significantly reduced if water heater installed anywhere except residential home, but this is true for all brands residential water heaters gas and electric. So if you move, and take Marathon with you, then warranty is voided. However by leaving the unit in old home, the new homeowner will benefit up to 15 years extended warranty assuming they have the purchase receipt.

Limited Lifetime Warranty

Tank: Lifetime
Parts: 6 year
Order extra elements.

Marathon Warranty/ Certificate of warranty comes with each product
Marathon warranty, and claim procedure
Rheem offers extended warranty for Marathon and for ordinary steel tanks
Limited LIFETIME tank / 6 YEARS parts
Privately owned, single family dwellings – the tank is warranted not to leak “for as long as you own your home”. If the home is sold, the warranty reverts to fifteen years from the date of the installation and the second owner received coverage for the time remaining. Parts are warranted for 6 years from the date of manufacture or 5 years from the effective date, whichever is greater.
Tank must be maintained as outlined in product manual

10 YEARS tank /1 YEAR parts
Apartments, condominiums, restrooms in office and commercial buildings, multifamily housing or any light duty commercial/industrial use – the tank is warranted for 10 years from the date of installation. Parts are warranted for 1 year from the date of manufacture.

Any application where water is used as process
5 YEARS tank/ 1 YEAR parts

Warranty Claims:

WHI Technical Service Department
Claim must be made within 90 days of in-warranty failure
Tip: Save plumbing contractor's invoice to verify installation date
burned out element

Elements fail frequently

Install smaller watt element.

Marathon elements burn out frequently

Install 3800 watt element to prevent early failure of elements.
Element installation page 18 manual
How to replace elements
Buy Rheem marathon elements from my affiliate links
Parts sheet

Some companies offer 'Lifetime Element Warranty' or '5-year element warranty.' Warranty means nothing if you cannot find foreign manufacturer. The company selling element is not the warranty carrier, and sellers generally do not underwrite warranty. Applies to all water heaters.
Marathon water heater

Marathon tank has 2-1/2" foam insulation

By contrast, most electric water heaters have 1" to 2" foam insulation.
However both Marathon and ordinary electric water heaters have same EF energy factor and same expected annual cost of operation.

Water heater blanket / recommended/ does not void warranty

Water heater insulation blanket can be installed on any electric water heater, including Marathon.
Do not install blanket on hybrid electric water heaters, or tankless electric.
Insulation blanket can cover entire tank and pipes (excluding TP valve which must be un-obstructed).
TP valve overflow tube installation code

Larger image or energy factor comparison chart
Compare Marathon EF / energy factor  (Higher EF is better)
"Energy Factor indicates combined thermal efficiency and standby efficiency of a water heater."  Government EF information site

There is no energy-saving advantage from buying Marathon vrs box store electric water heater because the EF ratings are same or very close.

Reference chart for typical box-store electric water heater
Reference chart for Marathon
Cost chart for all types water heater

Marathon energy cost It costs $400-500 per year to operate residential electric water heater
Same for Marathon or ordinary steel-tank electric water heater

Marathon does not save money vrs ordinary box-store electric water heater
Figures are for comparison only, and assume average household.
There is no energy-saving payback from buying Marathon

You can lower cost by reducing consumption, and/or re-wiring water heater for off-peak. Same applies for Marathon or any electric water heater.
9 ways to save with water heater
Off-peak options
Cost chart for all types water heater

First hour delivery is how much hot water can be used from fully heated tank before water turns cold. For example 40 gallon Marathon will deliver 52 gallons.
Same figures are typical for most electric water heaters. Exception: water heaters with 5500 watt elements, and when water heater thermostats are set for higher temperature
Recovery is how many gallons hot water the water heater can make in 1 hour.
Generally, all electric water heaters make 20-21 gallon hot water per hour with standard 4500 watt elements, or 18-19 gallon per hour with 3800 watt elements.
If Marathon elements are changed to 3800 watts, or water heater is wired for off-peak operation, the recovery number will drop, and it takes longer to heat water.

Contrast electric with gas: Gas water heaters will have higher first-hour delivery numbers, and higher recovery numbers. This is because gas heats water faster than electric. See chart
Water heater size chart

Choose correct size water heater

First hour rating (same as first hour delivery) chart generally applies to all water heaters
First hour rating can be increased by raising thermostat temperature

Homes with oversized bath or whirlpool bath: Install minimum 80 gallon electric, or 50 gallon gas
Size guideline
Size and specification

Home with 7 or more people/ install 2 water heaters  Read about 2 water heaters
Ways to increase amount of hot water
Marathon water heater thermostat
Marathon thermostats are factory set at 120 degrees
Raise temperature to increase first hour rating

Marathon thermostat has higher range than typical water heater

Typical steel-tank thermostat range is 90 to 150 degrees.
Marathon temperature range from 110 to 170 means Marathon water heater can supply more hot water if thermostat is turned up.
When temperature is higher, less hot water is used per shower, and more cold is added to moderate temperature. So Marathon can provide more showers. Read hot water scald advisory manual page 15
When temperature is set higher, the first hour delivery increases, but EF factor decreases and tank generally costs more to operate.
Temperatures above 140 can distill chemicals out of water that will harden inside plumbing pipes and valves. Temperature for killing bacteria is
140 Read advisories and cautions for hot water
Marathon TP valve, thermostats and elements are not generic parts available from local hardware. Marathon parts should be ordered ahead of time to avoid repair delays. Parts list
Select high temperature and regular temperature Marathon thermostats
How to replace thermostats
How to install meter on electric water heater
Change water temperature using timer
Control water temperature using Z-wave

High heat from solar

Solar water heater installation can produce hot water up to 180 degrees.
Ordinary tanks may warn against use as solar collectors because high heat and temperature will damage tank.
Rheem Martathon product literature does not mention solar.
Unknown if solar application will void product warranty.
Marathon is often used for solar applications, and saves buying special-order high-heat-rated steel tank
Remove sediment from marathon

Larger 1-7/8" element gives larger opening for cleaning out sediment.
Use element wrench SP610070, or buy 1-7/8" socket at local auto parts.

The SP610070 is ordinary cheapo element wrench, while auto parts socket will grab elements better
Marathon SP610070 element socket / Amazon

Marathon dip tube reduces sediment/ does not prevent sediment

Marathon dip tube can help stir sediments off bottom of tank, but this does not prevent sediment from forming.
Many new heaters offer same dip tube feature. Read about dip tubes
You can buy curved dip tubes that help prevent sediment and can install in any water heater. Dip tube site

Element advisory: Marathon elements burn out more frequently in some cases. Homes with hard water should install 3800 watt element to reduce sediment, and to reduce problem with elements burning out frequently.  Rheem Marathon parts list

Removal of sediment is easier with Marathon water heater, because element opening is larger.
Full efficiency is restored to all tank-type electric water heaters when sediment removed. Unlike gas water heater,  remaining sediment will not affect efficiency on electric since the element sits several inches above tank bottom.
Remove Marathon elements using 1-7/8" socket

All gas and electric water heaters that are exposed to hard water will form sediment deposits. Calcium-based sediments are not harmful, but must be removed periodically. All water heaters should be flushed every 6 months to prevent problems.  Read about sediment and flushing

Water heater element Buy:
Rheem marathon elements from my affiliate links
Professional 1-7/8" sockets

Parts sheet

Marathon element socket / Amazon

Marathon has Brass drain valve

Brass drain valve is more reliable, and will not crack and fail like plastic and can be repaired by replacing washer. If drain valve is dripping, screw hose cap over end of dripping drain valve.
Plastic drain valves will break off when removed, leaving broken plastic inside threaded port. This causes considerable work chiseling and drilling to remove pieces. How to replace drain valve

Leave access to drain valve when installing any water heater.
All water heaters should be flushed each 6 months to prevent sediment build-up. How to flush

Odor and water issues

Marathon does not have anode rod
Anode rod can cause odors in certain types of water
Purpose of anode rod is prevent steel tank from rusting
Marathon is not steel tank, does not need anode rod

Comparison: For ordinary steel tank: Install power anode rod can also solve anode-related odor problems.
Buy powered anode rod for steel water heaters up to 75 gallons

Marathon does not have anode rod because tank is non-metallic

Anode rods are installed in steel tanks to prevent rusting.

Marathon advantage: Homes that must replace anode rod frequently because of odor problems will benefit from Marathon water heater.  Read more about odors
Marathon does not eliminate all water heater odors, nor eliminate other water problems such as hard water, etc. If odor is present at all hot water faucets, and not at cold, then problem is inside water heater. But other causes can also cause tank odors such as dirt inside the line or inside the tank.

Typical anode problems are solved by installing Marathon:
1) Anode rod prevents rusting.  If steel-tank anode is not inspected and replaced each 2-4 years, then steel tank will rust, eventually leading to tank failure. Marathon tank will not rust and solves this problem.

2) Harmless bacteria is in all water. Some bacteria, usually found in well water, can react with anode rod inside steel tank. This reaction results in odor, requiring anode rod replacement, and/or periodic cleaning of tank with hydrogen peroxide. Marathon solves this problem.

3) Other rare anode problems can occur if steel-tank water heater has not been used for several weeks. Certain bacteria react with anode rod to produce hydrogen gas, which is flammable and explosive, and can ignite when faucet is first turned on and then light switch turned ON. Marathon solves this rare tank problem, but does NOT prevent natural gas from entering water well due to local hydrocarbon drilling and fracking.

Marathon under-counter water heater
Larger image

Marathon 120Volt under-counter water heater

15 and 20 gallon
22 x 36

Marathon Point-of-use sell sheet with specs
How to install under-counter water heater
Marathon water heater is lightweight
Drop 81 lb water heater on head will void warranty

Marathon water heater weighs less than steel tank

For example 40 gallon Marathon weighs 81 lbs, Marathon 50 gallon weighs 91 lbs
Contrast: typical 40 gallon steel tank weighs 100 lbs or more
This makes Marathon water heater easier to install
Two people should lift water heater to prevent damage

Marathon weight and specification chart
How to recycle or re-purpose old water heater
Marathon water heater connections

Marathon water heater connections

Read page 7-13 manual
Read warranty exclusions page 22

Electric connection: Read manual Page 10. Typical electrical connection is made with flexible conduit.
Use 10 gauge wire and 30 amp breaker for elements larger than 3800 watts.
Read label on side of tank to check element wattage. Wattage also printed on end of each element.
Marathon requires 10 gauge wire and 30 amp breaker

See wire sizes
See basic water heater circuit

Water connections: Cold and Hot must be connected to correct side, or water heater will not work as expected. If unsure which pipe: Before disconnecting old heater, run hot water for a few moments and feel which pipe is hot. Note also that incoming cold water pipe usually has shut off valve.

Vacuum relief valve: Do not connect anything to relief valve, except cold water connects at top.

TP valve: All water heaters today have temperature-pressure relief valve to prevent high-temperature causing tank failure.
Marathon water heater installation
Larger image
Use flexible copper to connect Marathon to water supply
Flexible copper connections are reliable. Use new flex lines, since old flex lines can leak
Insulate pipes completely when finished
Marathon installation starts page 4

Save $4.50 per year energy cost by installing heat traps Read about heat traps
Add #6 copper jumper wire between hot and cold pipes to properly bond water pipes

Do not make solder joints at water heater, or within 12" of water heater.
Otherwise heat from torch can damage Marathon tank.
Same is true for all water heaters. And all appliances.
Pre-assemble copper pipe and then thread pre-assembled copper pipe onto tank.
When using soldered joints instead of flexible connections, then plan for at least 12" space above heater. 
How to solder pipe

How to install TP valve overflow tube:

Applies to all water heaters
Use overflow pipe off old heater. Connections do not have to be water-tight, but joints must be secure so pressurized scalding hot water is released downward away from people. Overflow tube must be same diameter as valve discharge connection. Do not downsize pipe into smaller pipe. Overflow tube can have maximum 4 elbows and 30 feet length. End of overflow tube cannot be threaded. Tube cannot be lower than top edge of drip pan. Tube must terminate 6" above open drain. TP valve can draw water back into water heater if overflow tube is under water. Do not cap off TP valve or obstruct overflow tube.  Overflow tube cannot have shut off valve installed, or any obstructive valve. TP valve is first line of safety for water heater. TP valve releases water when pressure or temperature is too high, and prevents possible water heater explosion  How to test and replace TP valve
Water heater element

Marathon tank must be full of water before power is turned ON

All electric water heaters must be full of water before power is turned ON.
Otherwise elements burn out instantly.
Fill tank until bathtub tap runs full with no air gaps, then open Marathon TP valve for a moment to bleed last of air from tank. Then turn power ON. Marathon will heat 20 gallons per hour, so expect tank to be fully heated in 2-3 hours depending on tank size.
Remove Marathon elements using 1-7/8" socket
Read manual for advisories
Page 14 manual

Required maintenance

Maintain Marathon water heater
Warranty void or diminished if tank improperly maintained.
For example if water pressure exceeds 80-100 psi limit, or water temperature exceeds 180 degrees, or if TP valve not opened and tested each year.
Page 16 manual
Manual says to flush water heater each month, typical metal-tank water heaters say once per six months.
Troubleshoot Marathon water heater
Page 17 manual

Replacement parts and element installation for Marathon
Page 18 manual

Cleaning Marathon

'Car-bumper tough polyethylene exterior' can be cleaned with soap and water and/or grafitti remover
'Seamlessly blow-molded polybutylene tank surrounded by a filament wound fiberglass outer tank' is resistant to moist locations.

Hard water and Marathon

Install 3800 watt element to prevent early failure of elements.
Element installation page 18 manual

Upper 3800 watt, order part SP610130  
Lower 3800 watt, order part SP210197
marathon water heater

Marathon can resist water

Installation in damp or wet location might reduce warranty, but tank will not rust.
If water heater is flooded, the electrical parts can be replaced and water heater put back into service as soon as surfaces, covers and conduit channels are dry.

Warranty is reduced for wet location
Flooded water heater must be replaced:
Read about Flooded water heater

Recovery calculation maybe

Recovery = wattage divided by 2.42 divided by temperature rise degrees F
4500 watt/ 2.42 divided by 90 = 21 GPH
3800 watt/ 2.42 divided by 90 = 19 GPH
1 watt = 3.412 Btu
Marathon wiring
Larger image

Marathon is ordinary Non-Simultaneous water heater

Non-simultaneous means both elements are not ON at same time.
Upper element is ON, or lower element is ON, or both elements are OFF
This is typical for residential 240Volt water heaters
How electric water heaters work
How to troubleshoot electric water heaters

Water heaters can be rewired
How to wire thermostats
Advantage of electric water heater vrs gas water heater (Applies to non-hybrid electric water heaters)
Electric prices are stable. Electric heater avoids price fluctuations of NG and LP gas.
Electric water heaters can be installed anywhere inside a home as long as area does not flood. (Page 5 manual) No air supply required, while gas water heaters require fresh air for combustion. Can be installed in closet, or below grade, or in attic.
Electric needs no air supply. New gas water heaters can have FVIR problems and cannot be exposed to flammable vapors, or dust, or stored household chemicals.
Maintaining electric water heater is easier than gas. Gas water heaters require yearly service cleaning the air intake, burner and combustion parts
Electric heater are 'not as dangerous.' No danger of CO poisoning, or gas leak. No need for CO detector or gas detector.
Electric water heaters need no vent pipe, and do not draw air into house that will cause heat-air systems to run more.
Electric heaters are easier to install. Unlike gas water heaters, electric water heaters can be installed in direct contact with carpet, and personal belongings without creating fire hazard, assuming no obstruction over TP valve and wiring is up to code and inside approved conduit..
Electric heaters can be controlled by a timer and home automation. See timers
Disadvantage of Electric water heater vrs gas water heater
Burning coal to produce electricity produces more greenhouse gas than burning NG or LP gas. However power plant gasses are released at one central location instead of venting out at each home. Offsetting the lower carbon from burning natural gas, is that HVAC unit runs more because gas water heaters draw air into house from outdoors.
Yearly operating cost for electric water heater is usually higher than gas.
Gas heats water faster than electric, so gas water heaters have higher recovery and first-hour delivery.
Difference between gas and electric water heater EF energy factors
Electric water heaters have higher EF energy factor rating than gas water heaters. Higher EF is better.
Gas water heaters have lower EF, or worse EF than electric water heaters. But gas water heaters cost less per year to operate, despite gas water heaters having worse EF.
This is generally because burning gas releases more BTUs into water than electric. Gas heats water faster than electric.
Electric water heaters have higher EF rating because the element is immersed in water, and no heat is wasted up a vent pipe like gas water heater.
Gas water heaters can increase EF rating by recycling more heat from combustion by-product. This means less waste up the vent pipe. Read Effex water heater review
Gas and electric water heaters Support the economy:
Buy water heaters  from my associate links:

50 gallon Gas water heaters at Amazon
40 gallon gas water heaters at Amazon
50 gallon Electric water heaters at Amazon
40 gallon electric water heaters at Amazon
Hybrid / heat pump/ water heaters at Amazon

How to install gas water heater
Troubleshoot gas water heater
Troubleshoot electric water heater
Intermatic control centers Intermatic control centers:
+ manuals and parts

Intermatic freeze control centers
Intermatic basic control centers
Intermatic digital control centers
Z-wave water heater

Control water heater remotely

Control electric water heater with z-wave

Control gas water heater with remote control

Off-peak water heater strategies
box timers Compare box timers
programmable timer Compare programmable timers
Countdown timers Compare countdown timers

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