DESAGÜES (DRAINS) Version 3.0, our Sanitary and Storm Drainage Systems in Buildings Software, incorporates a tool that will allow for sump pits design, as well as for the operating point determination required to perform the respective sewage pumping station design.
Thus, you will now see in the PROJECT tab, a button in the Pumping panel.
This button will only be enabled if your project has a Sanitary Drainage network already defined and calculated.
In essence, the sump pump design process with DRAINS is quite simple, and, to demonstrate it, we will use our well-known example for a multi-family residential.
In this Sanitary Drainage Project, the software has calculated a total of 460 fixture Units discharging to what will be the sewage pump pit.
Here we will assume that a sewage pumping station is required to evacuate the total sewage water from the residential complex to the corresponding disposal point.
So, by pressing the button, the sewage Pumping Manager dialog will be shown.
Sewage Pump Pit’s Inflow Calculation
First of all, you will see that the program has converted the total Fixture Units calculated to wastewater flow inflowing into the Sewage Pump pit.
This conversion is done using the HUNTER’S method probable flows table that we have created for the project.
Here, in the Settings tab, Fixture Units Conversion Group, clicking this button will show the original HUNTER’S table, which is incorporated by default in the software.
But, if other values are used in your country, you have the option to modify it, affecting these original flow values for a factor that you must introduce here.
Let’s suppose I want to reduce them by 40 percent, so I’ll enter 0,6 here.
Then, by clicking this button, you will see the reduction factor applied to the original values.
It’s also possible to import data from Excel files. To do this, click this button.
Select the excel file.
From this dialog, select the sheet containing the data.
For each of these properties, a column or field must be assigned from the selected file.
And the respective flow units, in the original data, must be chosen too to perform the conversion to the project’s actual units.
By pressing OK, you will see them in the table, thus becoming the reference values for the sump pump design project.
In our case, we will use the HUNTER’S original table.
So I click Cancel.
Additionally, keep in mind that if plumbing fixtures with flux valves predominate in your project, you must check this box to tell the program to use the values in the last column of the HUNTER’S table.
Sump Pump Pit Design
Defined the inflow to the sewage pump pit, the next thing to do is determining the pumping station design flow.
By default, in the program, this value is obtained from the general recommendation that states it should be equal to twice the swage water inflow to the pit.
But, in case you do not agree with this criterion, you can easily cancel this automatic calculation by checking this box.
Thus you can enter the value that you consider convenient for the calculations to be carried out next.
In this example we will keep the automatic calculation, so we deactivate it.
Then you will see that the option to consider two layouts for the sewage pumping system is offered.
The wet configuration, with submersible pumping equipment, or the dry one, with the pump located outside of the sump pit.
Here the difference, in terms of the calculation carried out, is that in the first case you will not have the design button for the suction pipe enabled here in the pump’s calculations group.
In the group at the top, we have the information necessary to determine the sewage pump pit or wet well volume.
You can select a circular plan for the sump, in which case you must specify the diameter.
Or the rectangular or square plan, in which you will enter the respective length and width as I will do for this example.
Later it is necessary to enter the freeboard as well as the minimum water height that you deem appropriate, depending on the characteristics of the sewage pumping equipment you are planning to use.
Thus, we are ready to obtain the total volume of the sewage pump pit when clicking the calculate button.
Let’s ignore this message for now. When we design the pumping equipment, it won’t appear anymore.
We see that about four cubic meters sump pit is required. But, as you know, this volume is dependent on the number of starts you specify for the pump per hour.
In this case, I left it at the default value of six, but notice the change if I now increase it to eight and recalculate. The volume, as expected, is lower.
Of course, the operating or utile height has been calculated based on the previously established parameters. But, by checking this box, you can override the automatic calculation and enter the value that you consider appropriate for your sump pump pit design.
It is worth noting that you can modify the volume units also from the settings tab, Units group.
Sewage Pump Operating Point Calculation
Then you will see in the group below, in addition to the inflow and pumping flow values that we have already reviewed, the required parameters to perform the calculation and design of the sewage pump suction and discharge pipes.
And, of course, the necessary value to carry out the appropriate selection of the sewage pumping equipment: the pumping head.
Therefore, you must specify the static pumping height, taking into account that this value must be the difference in elevation between the highest point of the discharge pipeline and the sump pit’s minimum water level.
Then, to calculate the pump power, we specify the pump’s efficiency.
And, since it is necessary to know the head losses in the system, we must, in this case, carry out the design of the discharge pipe by pressing this button.
This dialog allows us to select the diameter of the pipe from the list of available sizes in the project.
This list is based on the values that you have previously entered here in the diameters library in the Settings tab.
At this point, it’s required to specify the Hazen and Williams friction coefficient to be used in the head losses calculations.
Since we are here, look in the Local Head Losses Calculation box, the two available options to obtain the fittings losses in the design.
When the Equivalent Length option Is selected, you must, for each diameter you have created in the diameters library, specify the equivalent length values for each of the fittings incorporated in the program.
Also, if you want to simplify the work, you have the option to calculate local losses by increasing the actual length of each pipe, in which case, you must specify the increasing percentage here.
Note that when this second option is selected, the list of available fittings will not be shown in the Pressure Pipes Editor dialog.
In this example, and it is what we recommend always to do, we keep with the equivalent length method.
So, coming back to the Pressure pipes editor, let’s specify here the quantities for the installed fittings in the discharge pipe from the sewage pump.
And I hit the Calculate Button.
Here we see that the specified diameter generates a very high velocity. Greater than the general recommendation of 3 meters per second.
So I change and recalculate until I get the expected result.
In this way, I have calculated the discharge pipe with the corresponding determination of its total head losses, which, as always, I can override the result and modify it by checking this box and entering the value that I consider appropriate.
Finally, it is necessary to click the calculate button here to determine the pumping head and the respective power.
Remember that if we choose the non-submersible equipment option, we will have to carry out the same calculation and design process for the pump’s suction pipe.
So we have the sump pit design as well as the sump pump operating point for this project.
Sump Pit and Pump Design Results Table
For the presentation of the design’s data and results, you can go to the Results tab and, you will see now, in the Reports panel, this button.
Clicking it gives you access to another new feature of the program: the project’s summary tables.
Here you will see that at the end is the Sump Pit and Pump table.
Also, you will find in the list of tables, the equivalent lengths calculation one, if you have chosen this method for the calculation of pressure head losses.
As always, you have the option to print these tables or export them to a Microsoft Excel file to give them the format of your preference.
Finally, you now have a useful tool to simplify the design process of the sewage pumping pits in your sanitary drainage projects.
DRAINS includes the tool for sump pits design as well as the sump pump operating point calculation, that may be required in any of your projects.
Once the building’s sanitary sewers network is finished, the program will convert the Total Fixture units into a probable flow to carry out the design of the sewage pumping station design.
It includes the options to specify the sump pit’s shape and, based on the pumped flow, the automatic determination of its total volume.
Also, for the sump pump equipment selection, you will find the pressure drop calculator for the suction and discharge pipes with which, together with the characteristics of the sump pit, determine the equipment’s pumping head as well as its power.