Final answer:
A water heater that is constructed and installed so that all air for combustion is derived directly from the outside atmosphere and all flue gases are discharged to the outside atmosphere is a direct vent water heater.
Step-by-step explanation:
A water heater that is constructed and installed so that all air for combustion is derived directly from the outside atmosphere and all flue gases are discharged to the outside atmosphere is a direct vent water heater.