Rheem Water Heaters has announced the availability of a new parts guide covering authorized replacement components and parts for all Rheem and Ruud brand water heaters, as well as for most other domestic makes and models. The newWater Heater Parts Guide 2005is a 75-page guide divided into three major sections: Preferred Parts for Rheem and Ruud brand residential water heaters, both gas and electric, and including elements, thermostats and various replacement parts; a second Preferred Parts section covering Rheem-Ruud commercial water heaters, including electric, heavy-duty gas, light-duty gas, and low NOx models; and Universal Parts for all makes of residential electric water heaters and certain makes of residential gas water heaters. Rheem Water Heaters.