Which of the following factors affect head loss due to friction?

The selection of density, temperature, roughness, and velocity as factors affecting head loss due to friction is correct because these parameters directly impact the resistance encountered by fluid flow in a pipe.

Density plays a role because it affects how viscous a fluid is. A denser fluid may result in higher friction losses since it typically has a higher inertia when flowing. Temperature influences fluid viscosity; as temperature increases, the viscosity of liquids generally decreases, which can lead to lower head loss.

Roughness is critical because the texture of the pipe's internal surface creates turbulence in the flow, significantly increasing frictional resistance. A rougher pipe will typically have higher head losses compared to a smoother one, due to increased drag and turbulence in the fluid moving through it.

Velocity is an essential factor as well; as the flow velocity of the fluid increases, the frictional head loss also increases. This is due to the greater interaction between the fluid and the pipe walls, leading to more turbulent flow conditions.

Thus, all of these factors together help explain the total head loss due to friction within a piping system, making them crucial for plumbing design considerations.