First of all, we need to forget about the word “exactly” in the title. When dealing with turbulent flow in water and wastewater systems, there is no theoretically perfect equation for head loss. All turbulent flow head loss equations for water are empirical to a certain extent. If you ask university faculty who teach hydraulics, they will tell you that the Darcy-Weisbach equation is the correct equation, and they will denigrate the Hazen-Williams equation. My fluid mechanics textbook from my school days, Streeter, Fluid Mechanics, did not even mention the Hazen-Williams equation. However, if you walk down the street to the local water utility or engineering consultant office, they will be using the Hazen-Williams equation. Why the discrepancy? There are some good reasons why the Darcy-Weisbach equation is theoretically better. It is based on a force balance between pressure and gravity forces driving the flow and the friction/turbulence restraining the flow. This equation applies to any Newtonian fluid, not just water at room temperature. It can accommodate not only a range of roughness but also a range of boundary layer types. Why don’t practicing engineers use Darcy-Weisbach? Looking at the Darcy-Weisbach equation below, everyone understands the independent variables: head loss

We regularly seek feedback from our users on how we’re doing. In a recent survey, we received excellent scores across the board on our OpenFlows products like OpenFlows Water and OpenFlows Sewer. One individual noted it would be great if Bentley were to “Provide additional training, demos, and webinars.”

The story of the history of water distribution system analysis (WDSA) is pretty fascinating, at least to me. There have been a large number of contributors to where we are today in water distribution modeling.

Just as there are classics in literature like Shakespeare’s Hamlet and Steinbeck’s Grapes of Wrath, there are classic works in water and wastewater.

I explained that a single hydrant flow test was pretty useless for evaluating system capacity or model calibration.

Isolation valves are essential components of water distribution systems. Without them, repairing a pipe break or performing other maintenance would require shutting down the entire water distribution system or resorting to some heroic work on pressurized pipes.