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.