Rinnai introduces a new line of condensing tankless water heaters, featuring a breakthrough in recirculation technology to help users save time, money and natural resources. Along with the recently introduced dual-venting options on interior units (RUC98i and RUC80i ), the RUD98i and RUR98e, the newest additions to the Ultra series condensing tankless water heater family, come equipped with an integrated pump, internal bypass line and thermal bypass valve, and will work with either a dedicated return line or a crossover valve.