Manifold Flow in Wastewater Pressure-Distribution Systems

By properly considering well-established concepts of theoretical and experimental fluid mechanics, inadequacies of methods in widespread use for wastewater pressure-distribution system design are revealed. Erroneous concepts include deficient consideration of pressure changes and velocity-head recovery in the manifold and lateral across takeoffs, and oversimplified, inaccurate consideration of the head loss in the branch (riser) entrance. Improvements are presented that can result in correct design with better performance and economy. For design purpose it is useful to have a simplified method for selecting design parameters for laterals and manifolds and a computer-based method to check and refine the design; that is the approach utilized by the writer and to be elaborated upon in a future paper. A larger perspective is also presented, by noting numerous other concepts of "established practice" that the author has overturned and for which he has provided corrective methods. This is offered as encouragement to others to not simply accept published design methods, but rather to critically review their validity and applicability and modify them for specific applications and more generally when appropriate.