What can cause unavoidable resistance to flow in a venting system?

In a venting system, unavoidable resistance to flow is primarily caused by physical barriers and changes in direction that disrupt the smooth passage of gases. Obstacles such as elbows, tees, and horizontal runs create additional turbulence and friction, which can hinder the proper movement of combustion byproducts. Each bend or angle in the piping can add a certain amount of resistance that needs to be accounted for in the design and installation of the venting system.

This resistance is inherent to the design of the venting system and must be carefully considered to ensure adequate venting performance. For instance, more elbows or longer horizontal runs can significantly increase the resistance compared to a straight, unobstructed path, making it essential for technicians to follow manufacturer guidelines and best practices during installation to minimize this effect.