Direct Vent Piping

How Does it Work?

Direct vent is a sealed, specially designed gas venting system which provides all of the combustion air to the appliance from outside the house through one pipe and which discharges combustion by-products to the outside through another pipe. Providing outside combustion air as part of the venting system and sealing out contact between the combustion process and the dwelling are the distinguishing characteristics of direct vent technology. Because they do not interact with the indoor environment, direct vent systems are less likely to be affected by normal negative pressure situations in a house.

Coaxial Direct Vent Systems

Coaxial systems use a pipe inside a larger pipe. The smaller pipe is centered and fixed in position with spacers in the larger pipe. Combustion products exit through the smaller inner pipe. Outdoor combustion air flows in through the space between the two pipe. Coaxial systems may be rigid or flexible.

Colinear DV Systems

Colinear systems use two separate pipes, which are usually flexible pipes. One pipe, usually smaller, brings in outdoor combustion air. The other, usually larger, pipe handles combustion products. The pipes may be the same size, so it is important to make sure the pipes are used and installed correctly.

Manufacturer's instructions may call for the exhaust pipe to be insulated and maintain minimum clearances to combustibles.