Tankless Water Heater installation, You will love this Marvel! Navien Tankless Water Heater all Stainless Steel. and talk to Steve about a Tankless Water Heater.. Year Warranty Rheem Water Heater. year warranty water heaters are the basic level series for Rheem. These are fantastic water heaters, but they do require annual maintenance to drain the tank. This prevents harmful mineral deposits from forming anding the gllining of the storage tank. These Rheem water heaters come with a year warranty on parts tank, and a year warranty on labor..To find the right Rheem Installation Guide either select the Product Category from the drop down menu or enter the water heater number below..If the water heater is being installed as a replacement for an existing power vented water heater, a thorough inspection of the existing venting system must be performed prior to any installation work..