Sewerage Calculation

Sewerage Calculation using Manning Equation For Vitrified Clay Pipe and Reinforced Concrete Pipe. The Excel spreadsheet titled “SEWER RETICULATION DESIGN CALCULATION” is used to design a sewer system by calculating various parameters for each section of the sewer line associated with different manholes. Here’s a breakdown of how the calculation works:

• Total Population Equivalent (PE): This is an estimate of the wastewater load produced by a population. It’s used to determine the size and capacity of the sewer system.
• Manning Coefficient (n=0.013): This is a constant used in the Manning Equation to calculate the flow rate in open channels like sewers. It accounts for factors like the roughness of the pipe’s interior.

For each manhole (MH), the spreadsheet calculates:

• Online Population (POPLN): The population served by the sewer section between two manholes.
• Cumulative Population (CUMUL POPLN): The total population served up to each manhole.
• Peak Flow Factor: An adjustment factor for peak usage times, which multiplies the average flow to account for times of high demand.
• Cumulative Flow (CUMUL FLOW l/s): The total flow rate at each manhole, considering the cumulative population and peak flow factor.

The Sewerline Details are calculated using the Manning Equation:

• Diameter (DIA mm): The internal diameter of the sewer pipe.
• Gradient (1 : X): The slope of the sewer line, which affects the velocity and flow rate.
• Velocity (VEL m/sec): The speed of the wastewater flow in the sewer line.
• Capacity (Q l/s): The maximum flow rate that the sewer line can handle.
• Length (m): The length of the sewer section between two manholes.

Manhole Details include:

• Fall (m): The vertical drop between consecutive manholes.
• Ground Level (GL m) and Invert Level (IL m): The elevation of the ground and the bottom of the sewer pipe at the manhole location.
• Depth (m): The depth of the manhole.
• Type: Indicates whether it’s a new or existing manhole.

The spreadsheet uses these calculations to ensure that the sewer system is adequately designed to handle the expected wastewater load from the served population.