Southside Plumbing replaced an existing Navien tankless unit with a new unit from Navien. The new model is the A2 instead of the A1 like the previous model. The gas line had to be completely reworked in order to provide the unit with proper gas flow. The existing venting was a little bit too low, so both the intake and the exhaust were raised up in height to avoid obstruction during snowstorms. A new expansion tank and new service valves were also installed with the new heater.