Rinnai introduces a tankless water heater that allows for both concentric or twin-pipe PVC venting from the same unit. These new Ultra Series condensing tankless water heater models, RUC98i and RUC80i, feature a built-in system with maximum flexibility for installers and dealers, who can now know that the unit they’ve specified or have on-hand will be compatible with whichever venting installation is preferred or required when they arrive on the jobsite. For concentric venting, installers simply remove and discard the exhaust adapter ring. For twin-pipe PVC configurations, the intake cap is removed and discarded. With the twin-pipe option, the installer can use 3” or 4” PVC/CPVC pipe for the intake and exhaust. Rinnai.