A vent apparatus is used to install a tankless water heater or similar equipment inside an attic without going onto the roof. The vent apparatus may include a main housing and an umbrella assembly movably disposed therein. The main housing (e.g., PVC pipe) is installed through the roof. The umbrella assembly may have a central rod with a flexible umbrella cover on top and an engagement member on bottom. The umbrella assembly is pushed up through the main housing until the engagement member hits the bottom of the main housing and the umbrella cover exits the top of the main housing to cover it and prevent rain from entering the main housing. The bottom of the main housing is then connected to the tankless water heater. Additional embodiments are disclosed for tankless water heaters with an air intake port and a gas exhaust port.

An exhaust pipe system for conducting exhaust gas from a combustion device to an exhaust system includes a first exhaust pipe with an inlet end and an outlet end, and a second exhaust pipe having a first line end and a second line end, wherein the inlet end of the first exhaust pipe is connectable to the first line end of the second exhaust pipe via a detachable coupling connection. A locking member is arranged to be movable between a closed position closing a passage and an open position opening the passage inside the first exhaust pipe. When the coupling connection is released, the locking member is automatically arranged in the closed position, and the second exhaust pipe has an actuating member which, when the coupling connection is established, urges the locking member into the open position.