4" Z-Vent Universal Appliance Adapter w/Backflow Preventer
Z-Vent 2ZVB04 is an appliance adapter, which connects to the 4" flue outlet of the Takagi tankless water heater and is used to adapt the unit to 4" Z-Vent pipe and venting parts. Has a built-in backflow preventer. This adapter is required for all types of installations.
