✔ Warranties
There are 3 main manufacturers that make all other brands: Rheem, AO-Smith, Bradford White. Most warranties are the same and protect against defects in workmanship.
Water heater manufacturers
Kenmore water heater warranty is printed in each product manual Example Kenmore water heater warranty
Rheem:  Example 6 year Rheem water heater manual from 2003
Rheem warranty claim form
Rheem parts warranty claim form
American Residential: Example American residential warranty 2006
Reliance power vent: Reliance power vent warranty
Rheem Marathon: Example Marathon warranty
GE Heat pump GE Hybrid water heater manual
GE: GE water heater warranties