Designing rainwater drainage installations

Product	InstalSystem 5
Type of article	DESIGNING LESSON
Source for translation	2023-12-06

Scope of lesson

This article presents the basic design path for the gravity rainwater drainage installation. The gravity rainwater drainage module is intended to design and calculate drainage network of a flat roof or another flat area, like a terrace. Gutters are not included, so tilted roofs are not in the project scope. The calculations are based on EN 12056-3.
The module is enabled by a separate checkbox in the Project scope. It has its own General data, piping and calculation options, element styles and own editing scope in the graphic editor and model view. The button to start calculations is shared with the sanitary sewage module, as well as Check connections button.

Modules and program configuration

InstalSystem 5 with the module:

Rainwater gravity systems.

Project file

The project file used in this lesson: Rainwater drainage installation in a multifamily building (example for the lesson).

Initial state

The project contains complete default data configured in the template file. The building structure has been elaborated on the basis of DWG layouts.

Steps to perform

Opening the project file

When creating a new design, select from the list the template that contains the default data for the drainage system,
(or): upload an existing building structure file - minimum content is correct ordinates and slab thicknesses.

Verify and correct if necessary data that has a significant impact on the geometry of the drainage installation:

the Ground elevation or the Ground modeling;
the Thickness of the slabs on particular storeys (ATTENTION! this may affect previously completed or planned designs of other installations in this file) - applies to terrace drainage;
the Elevation of roof top and shape of the roof if the file contains the complete building structure.

Editing the general project data

Fill in the default data in the General data window:

Project scope - determine project scope: Rainwater drainage systems.

1. Project scope.
Catalogues – select and move necessary catalogues to the Catalogues in project: table. To speed up the selection, the filters can be used. For more information, see: Using catalogues and catalogues data in the project.
Calculation standards and options – verify and correct if necessary:
- Precipitation intensity,
- Gradients and fill ratio.
  
  2. Calculation standards and options.
Rainwater drainage systems / Distribution system / Types and default data – append default types:
- Default pipe type: Rainwater drainage,
- Default methods of implementation of connections.
  
  3. Types and default data.
Verify and correct if necessary settings on the tab Pipe sizing options.
Storeys management – verify and correct if necessary:
- Point of passage of the stack to the collector - Determination of the ordinate of points, where the stacks turn into the drainage network. To be set for the storey on which the drainage network is drawn.
  
  4. Point of passage of the stack to the collector.
- Distance from the floor of the connection points to the stack - For a given storey, the default distance from the floor of the point at which the branches from the appliances will be connected to the stack. For each branch, this can be changed in the data table of the pipe-run connected to the stack.
  
  5. Distance from the floor of the connection points to the stack.
If the layout is the same on each floor, copy repetitive parts of the installation to other storeys using Copy selected elements to the storey above or Copy selected elements to multiple storeys function.

Editing the installation and its data

Carry out inserting and graphic editing operations using the AUTO and ORTO modes.

Select editing scope Drainage (R);
Insert the Drain elements: Roof gully and Drain, taking into account the building construction. Divide the catchment into parts according to the roof slopes;
Specify the Catchment area for each using the Area measurement function.
Insert the Stack elements and enter its data in the Data table window:
- In the Position section, declare the range of storeys of the Stack.
- Choose the Element on top of stack;
  
  6. Stack data.
  - For the Roof gully check and correct if necessary its Type and insert the value of the Catchment area;
  - For the case when the Connection to the stack above is chosen declare the point Connect to the stack having symbol and set the Distance from ceiling of the conn. to stack above.
Insert the Rainwater outlet and verify its position in the model. ATTENTION! In one rainwater drainage installation can be only one Rainwater outlet element. But there can be several installations in one project.
Connect the Stack with the Drain elements using the Rainwater drainage pipe-runs. If the Drain should be connected on an elevation different than the default, change Method of declaring the point of connection to the stack to User defined, then set manually the required value of Distance from the floor of connection to the stack.

7. Method of declaring the point of connection to the stack.
Connect Rainwater outlet with the Stack elements on the lowest storey to form the sewer collector network. This network is configured with consideration of the value of Point of passage of the stack to the collector set in the General data window.
(Optional) If needed, change the way of realizing chosen pipe-run's nodes to other than the default, set in general data. It is possible in the Data table window for the Junction element.
Insert necessary Fittings in the 2D editor or on the 3D view:Bypass bend and Sediment trap.
Choose the Type from available catalogues and, if necessary, adjust the Rotation angle.

8. Insert Fittings.

Verifying the correctness of the installation structure.

Verify the correctness of the connections of the installation components using the Check connections function (Shortcut: Shift + F2);
Verify the correctness of the installation structure using the 3D view;
Adjust the layout of the pipe-runs according to external factors, e.g. passages through walls, overlaps with other installations.

Running the calculations

Start the calculation of the Drainage systems by clicking in the Calculations section of the toolbar;
Сheck messages the Diagnostics window. First of all, eliminate Errors;
Verify and adjust if necessary the layout of the installation: gradients, collisions, overlapping junctions, etc.

After the calculations, the vertical passage of the installation can be corrected by:

imposing proper values in the Data table window for the Gravity stormwater drainage pipe-run element in the following fields: Real gradient, Elevation of first node, Elevation of second node,
dividing the chosen pipe-runs into parts and modifying their data.
It is recommended to implement such changes gradually and to observe their influence upon the system, as the change in one node after calculations may have a significant impact on positioning of its greater part.

Note: Defining the vertical passage of pipe-runs, the program does not exceed the value imposed in the Maximum gradient field in the General data window in the Calculation standards and options tab. This value is also automatically propagated to data of all pipe-runs. In case a difference of ordinates between the end of the calculated pipe-run and another pipe-run or a sewage outlet occurs, an additional vertical pipe-run is generated. To avoid it, allow for a greater gradient, by augmenting individually for each pipe-run a new value in the Maximum gradient field of the Data table and then recalculating the project.

Verification of results

After calculations, the system layout should be verified visually by means of the 3D view;
If the calculations end with at least one error, the layout may be unreliable;
The sized diameters of the pipe-runs and fittings can be verified directly in the drawings.

9. Visual verification in the 3D view window.
If a catalogue with visualisation of fittings (like tees, bends etc.) is used in the project, it can helpful in assessing the correctness of fittings selection and sizing for pipe-run nodes (junctions). To do so, node visualisation should be turned on in the General data window, on the Drawing options tab, or using the icon of the Installation elements' visibility directly in the 3D view.

10. Visualization of sewage fittings.

Note: By default, only the nodes with correctly selected fittings, for which there are no warnings in the Diagnostics window, are visualised.
Other forms of presentation of calculation results are: component labels and tables of results For more information, see: Presentation of the calculations result.

11. List of pipes, pipe fittings and couplings.

Preparing drawings for export/printing

To have the results for pipe-runs and installation nodes included in the printout of a drawing, appropriate labels must be inserted For more information, see: Preparation of drawings for export / printing.
Completed drawings can be printed and/or exported For more information, see: Export / print results and drawings.