Marathon Water Heater Warranty Guide
Manufactured by Rheem Manufacturing Company · Warranty info last verified: March 2026
Marathon water heaters are manufactured by Rheem Manufacturing Company. Warranty coverage on this page reflects one product line, the Marathon Electric Tank (All Sizes). On that line, the Marathon Electric Tank (All Sizes) carries a lifetime tank warranty, parts reach 6 years, and no labor coverage is included on standard warranties. The warranty is transferable to later owners at the same address, registration is required within 60 days of installation, and claims run through 800-374-8806.
Quick Warranty Facts
Tank / H.E. Coverage
Lifetime
Parts Coverage
6 years max
Labor Coverage
None
Transferable
Yes
Extended Warranty
N/A
Registration Required
Yes: within 60 days
Warranty by Product Line
Coverage periods vary by model series. Check your model against the table below.
| Product Line | Tank / H.E. | Parts | Labor |
|---|---|---|---|
Marathon Electric Tank (All Sizes) Lifetime tank warranty due to blow-molded polybutene tank that cannot rust or corrode. Parts (heating elements, thermostats) covered for 6 years. No labor warranty. Available in 30, 50, 85, and 105-gallon sizes. | Lifetime | 6 yr | None |
How to Register Your Marathon Water Heater
Marathon requires registration within 60 days of installation to activate full coverage on your Marathon Electric Tank (All Sizes). Missing that 60-day window can reduce your coverage, so complete it right after install.
You will need:
- Serial number (from the rating label)
- Model number
- Installation date
- Installer's name and contact info
- Your name and address
Have these ready before the 60-day Marathon deadline passes.
What's Covered
- Defects in materials and workmanship under normal residential use
- Marathon Electric Tank (All Sizes): a lifetime tank warranty, 6-year parts, and no labor coverage
- Lifetime tank protection on the Marathon Electric Tank (All Sizes) against tank failure
What's NOT Covered
Marathon lists 5 situations that fall outside coverage on its Marathon Electric Tank (All Sizes):
- Damage from improper installation
- Physical damage to the tank exterior
- Labor costs (no labor warranty provided)
- Parts after 6 years
- Damage from excessive water pressure or water hammer
How to File a Marathon Warranty Claim
- 1
Locate serial number on the rating label (MMYY format followed by sequence number)
- 2
Register your Marathon at rheem.com/warranties
- 3
Contact Rheem customer service at 800-374-8806
- 4
For tank claims under the lifetime warranty, Rheem will arrange tank replacement
- 5
Note: Labor is not covered - you will need to arrange and pay for installation
Marathon warranty line: 800-374-8806
Warranty Transferability: Yes
The Marathon lifetime tank warranty is transferable to subsequent owners because it covers the tank itself (which cannot corrode) rather than the installation. Confirm transferability with Rheem as terms may vary.
Additional Notes
The Marathon is Rheem's specialty electric water heater with a unique blow-molded polybutene (plastic) tank that cannot rust or corrode, which is why it carries a lifetime tank warranty. The tank is heavier duty than conventional glass-lined steel tanks. Parts (heating elements, thermostats) are covered for 6 years. No anode rod is needed because the tank is non-metallic. Marathon is an excellent choice for areas with corrosive water conditions.
Related brands with similar warranty terms:
Marathon Warranty FAQ
How many years does the Marathon tank warranty last?
The Marathon Electric Tank (All Sizes) carries a lifetime tank warranty from Marathon. Parts are covered for up to 6 years, and Marathon standard warranties include no labor coverage.
Can I transfer a Marathon water heater warranty to a new owner?
Yes. Marathon warranties are transferable. The Marathon lifetime tank warranty is transferable to subsequent owners because it covers the tank itself (which cannot corrode) rather than the installation. Confirm transferability with Rheem as terms may vary.
How do I check whether my Marathon water heater is still under warranty?
Decode your serial number with our free tool at WaterHeaterChecker.com to find the manufacture date, then compare it against the coverage for your line (Marathon Electric Tank (All Sizes)). You can also call Marathon at 800-374-8806 with your serial number.
What voids a Marathon water heater warranty?
Common warranty voiding issues for Marathon include: Damage from improper installation; Physical damage to the tank exterior; Labor costs (no labor warranty provided).
Does Marathon sell an extended warranty for the Marathon Electric Tank (All Sizes)?
The Marathon Electric Tank (All Sizes) carries only the standard Marathon factory warranty shown above; no separate extended plan is listed. Ask about dealer coverage when you call 800-374-8806.
What should I do if my Marathon water heater fails under warranty?
Locate serial number on the rating label (MMYY format followed by sequence number). Then register your Marathon at rheem.com/warranties. The Marathon warranty line is 800-374-8806.
More for Your Marathon Water Heater
Not sure which of Marathon's models you have?
The Marathon Electric Tank (All Sizes) is Marathon's tank line covered here. Decode your serial number to confirm its age and estimated lifetime warranty status.
Decode Your Marathon Serial NumberThe coverage figure shown above was last verified in March 2026 and is provided as a helpful reference only. Warranty terms are set by Marathon and may change at any time. Always refer to the warranty certificate that came with your water heater for the definitive terms of your coverage. WaterHeaterChecker.com is not affiliated with Marathon or Rheem Manufacturing Company.