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Marathon water heater elements
Elements are probably weakest point of marathon water heater because they burn out frequently, and are non-generic, and expensive.



Marathon elements
Note ...Marathon upper element has 'internal fuse' (a resistor) that might prevent dry fire ... when upper element burns out ... caused when power is turned on before the tank is full of water.

In real world testing, the Rheem resistoried element is not 100% proven benefit, except Marathon elements are expensive.
And if you fill tank completely with water before applying power, then Marathon upper element won't dry fire ... and then if you choose, then Marathon upper and lower elements are interchangeable as long as length of element does not conflict with tank diameter.

Lower element does not come with a resistor or need a resistor since only the upper element will burn out if power is applied to tank before tank is full of water.

Either upper or lower Marathon element can be resistorized, and either element can be 4500 watt or 3800 watt or 3000 watt etc, but typically Marathon upper elements are 4500 watt for slightly faster heating, while lower elements are 3800 watt to help prevent burn-out, since lower elements run more hours than upper elements ... which is true on all residential water heaters.

13.3" length elements for 40-50 gallon
16.5" length 50, 75, 85, 105 gallon models.

Rheem marathon elementBuy best value:
-SP610160/ 13.38" 4500 watt
Copper .. Is listed at Rheem and in Marathon parts sheet as resistorized upper element

-SP213790 14" 4500 watt
Titanium resistorized upper element

-SP213670/ 16.5" 4500 watt
Titianum non-resistorized lower element

Other choices
SP210197/ 3800 watt
SP210201/ 3000 watt
SP210198/ 3800 watt
SP213480/ 3000 watt

SP213540/ 2000 watt
120 volt Point of use element

A new gasket is provided with each new element.
A new washer is usually needed each time an element is taken out of tank, for example when cleaning the tank.
 Possible Part # for Marathon gasket is SP310060 with 1.4" inside diameter, except the Marathon element opening is 1.5" and so the SP310060 gasket is slightly too small by .3".
Contrast with ordinary water heater, the gasket part # is SP6708 with 1.2" inside diameter while the element opening is 1.0".

http://waterheatertimer.org/pdf/Rheem-Marathon-parts-2.pdf
Read parts .pdf before buying
Resources
2020 marathon replacement parts
2020 3-phase light duty parts
2011 Marathon parts sheet/ pdf
2011 other parts
Tank parts
Regular water heater elements/ identify and replace
Resource
See all Marathon .pdf  manuals on this site

Question from Bob:
 Do I really need resistorized upper element if I am smart enough to never dry fire the upper element?
Seems to me its just another part to fail.
Dry fire
Answer: A Fused upper element is NOT required for tank to operate normally.
Dry fire is caused when tank receives power but tank is not full of water.
The upper element burns out instantly. The resistorized element offers 'resistance' to dry fire, but is not 100% prevention.
Lower element is not affected by dry fire because Marathon tanks are wired for non-simultaneous operation.
Fuse is not ordinary fuse that you can reset... it is a resistor that is added inside head of element.
Upper element dry fires.. but lower element typically does not.
No other manufacturer 'installs resistorized' elements, and there is no science that proves benefit to end-user.

Bob asks, Why is the upper element affected, but not lower element?
Because 30 amp residential water heaters (including Marathon) are non-simultaneous, which means upper element receives power first... so it is first to burn out. With non-simultaneous water heater, the lower part of tank never receives power until upper element has heated top of tank ... but if upper element dry fired, the top of tank never gets heated, so lower element never receives power... and lower element is fine, not burned out.
Symptom of dry fire is that heater will not produce any hot water.
Resource
How electric water heaters work

Marathon elements are expensive by comparison to ordinary elements.
If you dry fire ordinary element, the replacement cost is $20 from local hardware store.
Marathon elements are not available at local hardware, and cost more
Resources:
How to wire thermostats
How thermostats work
Bob says:
I think I will get the marathon titanium element for the upper because of the way I use my water heater as a solar energy battery, the upper does come on a lot.  Much more so than in a standard instantaneous grid install.

My opinion: the condition of water is probably more of an issue, but everybody's experience is unique, so it's hard to find a common thread that fits all sizes.
Better value?
SP610160/ 4500 watt copper/ non-fused/ Best value

Steve asks about element for 105 gallon Marathon MR105245
I have a MR105245 B 0905w56019  Marathon water heater and would like to replace the elements as a precaution.  I would like an upper and lower element.

Answer
Rheem has several new models, but your 105 gallon model appears on the 2008 spec sheet, so I am attaching 2011 parts sheet.
The 4500 watt lower element is 16.5" 3800 watt SP213670, and 4500 watt upper element is 14" 4500 watt SP213790.

I suggest just buying the cheapest element ... from links on this page, or if elements burn out frequently, use 3500 watt instead of 4500 watt. Pay attention to length so you don't get short element that fits the 20 gallon tank.
Resources:
Marathon-2008-Spec-Sheet.pdf
Marathon-parts-sheet-2011.pdf
Older warranty. pdf

If your heater is old like 2008 etc, your tank probably still has limited lifetime warranty for residential installation, but warranty does not cover elements and thermostats.
You lifetime warranty might not cover 105 gallon without you paying more to upgrade to the commercial-grade 100+ gallon tank.
Older resources
Marathon-Water-Heater-Warranty.pdf
Policy for Rheem- water heater innovations Marathon warranty.pdf

Thermostats
Today's Marathon has thermostat temperature range of 90-150°F ... vs older models that generally had higher temps 110-170°F.

Marathon is lighter weight than steel tank, making it easier to install, and does not need anode rod like steel tank since Marathon will not rust. Marathon can be exposed to moisture with diminished warranty, while steel tanks must have dry location.

Marathon has exactly same energy factor as regular steel metal tank.... UEF .88-.92, with actual overall efficiency of .91% to .84%, with larger tanks having less efficiency due to more surface space causing more heat loss..
Marathon does not have higher efficiency or more insulation value than ordinary steel tank.

Marathon tank has limited lifetime warranty for residential installation, as long as you own your home.
Warranty also covers parts for 6 years when heater is installed by instructions given in manual.
Resource
2020 manual
2020 spec sheet
2020 warranty
2009 Water heater Innovations warranty

Marathon can be installed in damp location without risk of rusted tank, but the heater has reduced warranty coverage.
Resource
Read review Marathon water heater
2020 Marathon-specification-sheet.pdf
Marathon-parts-sheet-2011.pdf
Do your Marathon elements burn out frequently?
Solutions:
Hard water, acidic water, and other water conditions contribute to burn-out.
Turn up water softening, have water tested for condition, install good filter on incoming water.
Install lower wattage elements ... replace 4500 watt with 3800 volt ... and you get slightly slower heating.
Select the foldback or low density elements so element has more surface area, so the heating is spread over wider area and element still gives 3800-4500 watt of heating but element is not as hot.

Reduce temperature on both thermostats ... or reduce temperature on lower thermostat since it tends to run more hours than upper thermostat.
Typical shower bath is 104°F.  Turn down thermostats ... from 120° to 112°F. Higher temperatures percolate more chemicals out of water, and will increase sediments that affect element.

Reduce temperature on thermostat will also reduce first hour delivery, or reduce amount of usable hot water inside a fully heated tank, but to compensate, you can add another 240 volt line and then rewired thermostats for simultaneous operation to increase delivery:
Resource How to rewire for simultaneous operation
Change tank wiring will void tank warranty.

Resource:
Marathon thermostats
Removal of sediment
All gas and electric water heaters that are exposed to hard water will form sediment deposits that can cause element to burn out.
Calcium-based sediments are not harmful to potable (drinking) water, but must be removed periodically to prevent elements from burning out and to maintain efficiency.
Read about sediment and flushing

Sediment removal is easier with Marathon water heater, because element opening is larger (1-1/2" diameter vs 1" for ordinary steel tank).
Full efficiency is restored to all tank-type electric water heaters when sediment is removed. Unlike gas water heater,  remaining sediment inside electric heater will be at very bottom of heater and not affect efficiency since element sits inches above tank bottom.
Remove Marathon elements using 1-7/8" socket.

Buy:
1-7/8" socket
Rheem marathon element wrenchRheem marathon element wrench
The SP610070 is ordinary cheapo element wrench, instead buy socket and handle online or at auto parts store to remove elements easier.
Do not use impact wrench for removal or re-installation of Marathon element.

Elements are installed 'snug-tight' ... not torqued heavily. Threads do not require teflon tape of other sealant. New rubber gasket is required on every element replacement so element will seal.
Buy:
1-7/8" water heater element wrench/ Use screwdriver for handle
Professional 1-7/8" sockets/ use ratchet

Buy socket:
1-7/8" socket with 3/4" drive
1-7/8 sockets at Amazon
24" breaker bar with 3/4" drive

Thermostats and elements
Marathon Upper thermostat
Upper thermostat
Larger image
Marathon Lower thermostat
Lower thermostat
Larger image
Marathon is ordinary non-simultaneous residential water heater
30 amp breaker, 10 gauge wire, 4500 watt elements.
Same EF and efficiency as ordinary steel tank, nothing special except lifetime warranty, tank is made of polybutene instead of steel, will not rust, does not require anode rod, ... downside is elements can burn out frequently, elements cost a lot to replace and are not generic.
Thermostats are generic off-the-shelf, and are widely available.
Residential installation: limited lifetime warranty on tank and 6 year warranty on parts. Online registration required.
Commercial installation: 5 year tank, 1 year parts.
Resources:
2020 Spec sheet
2020 manual
Review Marathon water heater

Marathon Upper and lower thermostats are generic
Installing any ordinary thermostat will not void produce warranty
Resource
Marathon parts sheet/ pdf
Identify Marathon thermostats
Inspection finds leak around Marathon element
: Leaking element on Marathon should have little effect on brass threads where elements screw in, and leak will not cause rusted tank, because Marathon is Polybutene, not steel.

Some marathons experience damaged metal plate that holds thermostat. The problem usually accompanies a leaking element, but unknown if deteriorated plate caused the leak, or the leak caused the deteriorated plate.

Steel tank vs Marathon poly tank: Leaking element can damage ordinary steel tank, causing rust, and possible short circuit.
Long term leak on ordinary steel tank can rust the threads on element opening so element will never seal and heater must be replaced.

Resources
Leaking marathon element with damaged plate
Replace element and gasket
Leaking water heater resources

Marathon thermostats High temperature commercial thermostats:
Commercial use thermostats will fit Marathon.

Mararthon heavy-duty has 170°F thermostat range.

Voids product warranty for most tanks, including light duty Marathon tanks.
high temps risk scalding and very serious burns..

Buy: Rheem Upper thermostat:
Camco 08304
Rheem SP8293
Rheem SP8293
Rheem SP8294

Buy: Rheem lower thermostat
Rheem SP8295 / 170°
Camco 08314 / 180°
Upper and lower thermostats
thermostat temperature range
Ordinary residential upper and lower thermostats/
 rated 150 ℉/ fits any Marathon 120-240 Volt water heater

Thermostats are interchangeable/
Each works with Marathon water heater

Buy: 90-150 degree F for residential tank:
Water heater thermostats at Amazon
Camco thermostats at Amazon
More thermostats

Therm-o-disc thermostat protectors
Thermostat protectors fit any therm-o-disc thermostat
Protectors cover the electric terminals.
When you adjust temperature, or push reset button, covers will protect you from electric shock

Buy:
SP310040 upper protector
SP310010 lower protector
Marathon bushing ... convert element to regular element
Discontinued product
Voids Marathon warranty, but when installed, the bushings allowed customer to use ordinary cheapo elements from local store, instead of expensive Marathon elements.

For a shop wanting to fabricate a brass bushing, Marathon probably has 1.5" UNF straight fine thread with 12-14 threads per inch.
Thread on ordinary steel tank element is 1" NPSM straight thread with 11.5 threads per inch.

Resource:
Marathon bushing




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