A Legacy of Accuracy. For decades, Hach Flow Products and Services, along with our legacy brands Sigma and Marsh-McBirney, have been leading the open-channel wastewater flow monitoring industry. From utilizing new technologies for the improvement of tried-and-true flow monitoring practices to innovating completely new ways to approach the industry, Hach Flow has pioneered both approaches. And we have the case studies to prove it. Following are examples of our products and services in action. Please feel free to Request Additional Information if you’d like to see additional case studies on a particular product or service.