PE Exam Practice Problem #43: Water Resources | Sewer Designs - Equivalent Flows - Mannings Equation

Welcome to SolvedIn6: Free practice problems for the Professional Engineering Exam! Each question is styled after those created by the NCEES, and is usually solved in under 6 minutes, which is the average time you will have to solve each question on the Professional Engineering Exam.
In this problem, there are two 12-inch sewers draining to a junction manhole, which then drains into a third 12-inch sewer at a different slope. To find the slope of this sewer, we can perform the following steps.
Step 1: Use Mannings equation. Set up Mannings on both sides of an equation. One side will be for the 2 upstream sewers, and the other side will be for the downstream sewer. Cancel out terms and solve for the slope of the downstream sewer.
Step 2: Use Mannings equation again. Solve for the velocity in the downstream sewer using the slope you calculated in Step 1.
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