Draft on sewer design with software


The topic is not so simple as could appear. Starting from the beginning, what is the final aim? The dimensions of each pipe of our sewer system.
The steps to do that are:

  1. Design the planar view of the sewer system;
  2. Evaluation of the maximum discharge for each pipe;
  3. Calculation of the pipe’s diameter, as a consequence of 2 and 3

Design of the sewer system

So we need a sewer system, that can be create based on the urban destination of the area and of the position of the roads. In this draft is done with QGIS interfaced by GISWATER.
In this way is possible to obtain an input file for EPA-SWMM.

Evaluation of the maximum discharge

The discharge is a result of the simulation done in EPA-SWMM. However this result is based on different models (for infiltration, evaporation, etc) with different complexity. So to evaluate the maximum discharge in a node is necessary that the user select the appropriate part of the models. This is also done using GISWATER.

Calculation of the pipe’s diameter

At this point, the calculation of the diameter related to the evaluated discharge is very simple. Once the maximum discharge is estimated the diameter is directly obtained through the Gauckler-Strickler relation.

Install all the software


The software used in this exercise are three: QGIS works on all operative systems, GISWATER and SWMM (with GUI) only on Windows. So for the complete design you need (unfortunately) a working Windows OS.

How to install the software

To install QGIS 2.18 click here. ( To install QGIS 2.14 click here. )
To install GISWATER click here.
To install EPA-SWMM click here.

The “flowchart” of the design

To explain better the path of how use these software to design a sewer here is reported the flowchart-like scheme of the complete project:sewer design

Use of the software


QGIS is an Geografic Information System. It can be use to represent spatial quantities and infrastructures. In this case, aqueducts and sewers. To learn how to use QGIS please refer to QGIS Documentation. Instead, to understand how to use QGIS interfaced with GISWATER follow these series of videos that explain very well how to do.

The result of the use of GISWATER is an input file with all the GIS based and other fields fully filled directly in QGIS. To understand how to do that follow these other videos.


What is Docker?

Docker is lightweight virtual machine that simulates a Linux environment. It allows to abstract the characteristic of any operating system, and make easy the management of programs/models that needs to work everywhere. Here the complete official explanation.

Why Docker?

Because it makes our life easier and is a OS-free tools. Unfortunately, the first step above is not OS-free, because GISWater does work only in Windows, Docker can allow to replace the use of EPA-SWMM GUI which is also OS dependent.

How to install Docker?

To install DOCKER click here.

How use Docker?

For general uses of Docker please follow the official site documentation.
In our case the use its very simple, just follow below scheme:

In this post case we use a standard example of SWMM. To prepare the simulation first prepare a directory (say SWMMex) and put inside it the files you find at the following this link.

The steps to do to run the analysis with Docker are:

  1. Launch the Terminal: Quickstart Terminal for Docker Toolbox or Command-line/PowerShell Terminal for Docker;
  2. Move into the working directories where there are the input files: use the command cd to do that;
  3. Verify if the files are inside the directory: type ls and all directories and files should list, if not check if you are in the right directory;
  4. Launch the command depending on OS and Docker tool you are using: actually the commands are two..
    1. With Quickstart Docker Terminal or Command-line Terminal on OS X and Linux OS:
      docker run --rm -v $(pwd):/data ftt01/swmm5.1 <name of input file without extension>
    2. With Docker in PowerShell on Windows OS:
      docker run --rm -v ${pwd}:/data ftt01/swmm5.1 <name of input file without extension>

    NOTE: is meaning that if the file is called 2D.inp the command should be
    docker run –rm -v $(pwd):/data ftt01/swmm5.1 2D

  5. A directory with the same name (i.e. 2D in the case above) of the input file should be created, with the tree explained before. If not something went wrong! Check to have done all previous steps right.

For any problems related on Docker errors please check inside the installation post depending on your OS and Docker/Docker Toolbox choice or the Official troubleshooting page (here for Docker Toolbox).


If you prefer the GUI old way, please follow the manuals on the EPA-SWMM official page downloads. It doesn’t create a directory tree but you can manually copy the data from the report file.


The right way is to create a pipe, an area and a node. Analyze this, dimensioning the pipe. Then create the second pipe, area and node and so on.
The way that we adopted is a bit different due to software limits. So here the steps:

  1. Create the entire sewer tree on QGIS and set up with GISWATER:
    • Draw the sewer on QGIS following plan rules;
    • Set first dimension of the pipes;
    • Set other dimension with QGIS tools;
    • Set the constant intensity of rainfall for different time obtained from DDF (LSPP);
    • Set all the models to use in the analysis;
    • Run GISWATER for each different rainfall time to obtain an input file.
  2. Run Docker (and so behind it SWMM) to create the directory tree;
  3. Evaluate the maximum discharge and the diameter of each pipe starting from externals:
  4. Check if the entire sewer system respects law and technical aspects (degree of filling, velocity, etc).


This guide is under construction, so every advice, improvements and comments are appreciated. Thanks for reading!
Thanks to Prof.Rigon for the needed corrections.

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Published by Daniele Dalla Torre

I'm a Civil Engineering but I love to learn everything about technology, from the basics to the new frontiers! Here my gpg public key!

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