You are required to size a single-barrel inverted siphon (depressed sewer) under a small stream….
You are required to size a single-barrel inverted siphon (depressed sewer) under a small stream. The inverted siphon is 75 m long with a Hazen-Williams C-factor of 120. You would like to maintain a velocity of at least 0.6 m/s even at low flow. Important elevations are shown in the following figure.
Try diameters of 600, 750, and 900 mm. You would like to select a pipe that will not surcharge the upstream manhole, yet will carry a minimum flow of 300 L/s at a velocity of 0.6 m/s and a maximum flow of 2000 L/s. The downstream gravity sewer has enough capacity to set the water level in the downstream manhole to 310.00 m. For each diameter pipe, draw a curve of flow vs. upstream head and flow vs. velocity. Using the graphs, select the optimal pipe size and justify your decision.