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Exactly How Bad Is the Hazen-Williams Head Loss Equation for Water and Wastewater?

First of all, we need to forget about the word ā€œexactlyā€ 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

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Do You Need Help? We Have It.

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 ā€œProvide additional training, demos, and webinars.ā€

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A Family-Owned Company on a Mission to Ensure Access to Water and Sanitation for All

TSA – Tecnologia em Saneamento Ambiental (which translates to Technology in Environmental Sanitation in English) has a passion for the betterment of the communities they serve. TSA’s headquarters are in Porto Alegre, in the state of Rio Grande do Sul in Brazil, but they also work on projects that support cities across the southernmost part of the state. This family-owned business focuses on designing resilient and efficient water and wastewater networks. Engineers JosĆ© Vilmar Viegas and Matheus Viegas —a father-son team—and a handful of other employees work hard to bring a better quality of life to underserved communities. Their goal is to design water infrastructure that will grant access to water and sanitation services and improve water networks. These projects are key to social and economic development and that is what drives JosĆ© Vilmar and Mathues to do this work. Connected Data Brings Real-World Impact In Brazil, the most vulnerable communities lack access to water and sanitation systems. Many people live along rivers where raw sewage is dumped and are exposed to it daily. They also deal with intermittent water services that do not meet potability standards. TSA knows that by designing reliable, effective, and efficient sustainable sewage networks, they

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Are Two Heads Better Than One?

When I started in the water profession many years ago, there was a clear distinction between the American Water Works Association (AWWA) and the Water Pollution Control Federation (WPCF), now known as the Water Environment Federation (WEF). AWWA dealt with drinking water while WPCF handled wastewater.

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How Many Isolation Valves are Enough?

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.

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