Roof plumbing vents and methods including for tankless water heaters with concentric venting

A vent apparatus comprising:

• a main housing having an upper end and lower end;
• and
• an umbrella assembly including a central rod, a lower member, at least one stabilizer member, and a flexible upper cover, the lower member being adapted for engagement with the lower end of the main housing, the at least one stabilizer member being attached to the central rod above the lower member, the flexible upper cover being secured to an upper end of the central rod above the at least one stabilizer member,
• the lower member including a body and a lip disposed around the body, the lip being adapted for engagement with the lower end of the main housing, the lip being engaged with the lower end of the main housing when the flexible upper cover is in a deployed position above the upper end of the main housing.

A concentric vent assembly comprising:

• an outer housing having an inner surface and an intake passageway, the intake passageway extending away from the outer housing and in communication with the inner surface of the outer housing;
• a main housing having an upper end and lower end, the main housing have a flex cap disposed around the main housing and between the upper end and lower end of the main housing, the main housing being disposed within the outer housing and defining a flow passageway between an outer surface of the main housing and the inner surface of the outer housing, the flow passageway extending from an upper end of the outer housing to the intake passageway;
• and
• an umbrella assembly including a central rod, a lower member attached to the central rod, and a flexible upper cover attached to the central rod above the lower member, the lower member being adapted for engagement with the lower end of the main housing, and the umbrella assembly being adapted for slidable engagement within the main housing.