Final answer:
The pipe that connects a fuel-gas-burning water heater to a gas vent or chimney is called a flue pipe.
Step-by-step explanation:
The pipe or duct that connects a fuel-gas-burning water heater to a gas vent or chimney is called a flue pipe. This pipe is specifically designed to safely carry the exhaust gases produced by the water heater out of the building. It is usually made of metal and has insulation to prevent heat loss.
The flue pipe is an essential component of the water heater system, as it ensures that the combustion byproducts are properly vented to the outside. Without a flue pipe, the exhaust gases could accumulate indoors, leading to the risk of carbon monoxide poisoning.
In some cases, the flue pipe may be connected to a larger vent pipe or chimney pipe, depending on the design of the building and the specific requirements of the water heater. These pipes provide further ventilation and help to safely disperse the exhaust gases.