I was told by the Rheem rep that the difference between the 6-9 and 12 year warranty's is the 6 is un-lined the 9 and 12 years are coated and different metals.
Researching this - Rheem is not enjoying a very good reputation of late, and yes it does seem that there are various grades of models dependent on where purchased even on the exact same model. Must be something relatively recent as the last Rheem I installed 10 years ago at a different home) was flawless until I sold that home last year. Power vent type 50 gal. natural gas. My only bitch is there was no back draft damper on the flue nor is any type of one supplied. I acquired one and installed same. So it is possible that some of the complaints about leaks I have read are related to this,as in new install and not reading the little tid bit about first firing and possible condensation. Additionaly cold moist air flowing backwards ( no back draft damper) when the unit is not actively heating and again condensation- course for the average home owner this would be way way over their heads ( and for some of the techs also). Old guy little bit of everything stuffed in my noggin. ( no standing pilot as in the olden times)
