In general, increasing pipe diameter while keeping the same flow rate primarily affects which hydraulic parameter?

• A. Friction losses
• B. Pressure drop at the controller
• C. Water quality
• D. Electrical current in the pump

Answer: (C)

Increasing pipe diameter at the same flow rate lowers the fluid velocity (since Q = A × V). Slower movement means less wall shear and fewer interactions with the pipe surface, so friction losses in the pipe drop. Because these friction losses are what cause pressure to fall along the length of the piping, a larger diameter reduces the overall pressure drop in the line. Water quality by itself isn’t dictated by pipe diameter; it’s mainly influenced by source quality, treatment, and residence time, not the size of the pipe when the flow rate is fixed. Electrical current in the pump is linked to the head the system must overcome and the motor’s efficiency, which can be affected indirectly by reduced friction losses, but the primary hydraulic parameter changed here is the friction-related pressure drop in the piping.