Marathon Water Heater Warranty Guide
Manufactured by Rheem Manufacturing Company · Warranty info last verified: March 2026
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
Registration is required within 60 days of installation to activate full warranty coverage. Don't skip this step. Missing the deadline may reduce your coverage.
You will need:
- Serial number (from the rating label)
- Model number
- Installation date
- Installer's name and contact info
- Your name and address
What's Covered
- Defects in materials and workmanship
- Tank leaks from manufacturing defects (during tank warranty period)
- Internal component failures under normal use
- Heat exchanger failure (for tankless units)
- Manufacturer's defects discovered during warranty period
What's NOT Covered
- 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 long is the warranty on a Marathon water heater?
Marathon offers a lifetime tank warranty on certain models. Other models have tank warranties ranging from null to null years. Parts are typically covered for 6 years and labor for 0 year(s).
Is a Marathon water heater warranty transferable?
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 if my Marathon water heater is still under warranty?
Use our free serial number decoder at WaterHeaterChecker.com to find your manufacture date, then compare the age to Marathon's warranty period for your model. You can also contact Marathon directly 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 offer an extended warranty?
Marathon does not currently offer a standard extended warranty program. Contact them at 800-374-8806 for current options.
What do 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. Contact Marathon at 800-374-8806 for assistance.
More for Your Marathon Water Heater
Not sure which Marathon model you have?
Check your Marathon water heater's age, model info, and estimated warranty status with our free serial number decoder.
Decode Your Marathon Serial NumberThis information 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.