How to Calculate Total System Head

There are 2 parameters needed for the Pump Station Direct selection tool to be able to choose the correct pump for your application. These are the Flow Rate and the Total System Head.
· Flow Rate: This is the number of litres per second (L/s) that the pump is required to discharge. In a stormwater situation this would involve inputting the size of the catchment area, and the location in Australia and the calculator will find the rainfall data for that area and determine the flow rate required. In a sewerage situation, the flow rate required will depend on the number of people (PAX) being serviced.
· Total System Head: The higher the system head, the less flow rate a submersible pump will do.
Understanding how to calculate the Flow rate and Total System Head (TSH) is simpler than it seems. This guide will walk you through how the selection tool calculates TSH. For calculating flow rate, check out our ‘How to Calculate Flow Rate of a Pump’ blog.
What is Total System Head?
Total System Head refers to the energy a pump needs to move water from one location to another.
Accurately calculating TSH ensures the pump system operates efficiently, avoiding underperformance or overwork that could lead to system failure.
Calculating Total System Head
Enabling the online selection tool to calculate Total System Head involves understanding the site plan or information that’s been provided by a plumber or engineer. You’ll need to identify key parameters such as the vertical lift and the rising main details. Whether the information is readily available or requires calculation, this guide equips you with the knowledge to complete the selection process with confidence. For any uncertainties, consulting with an engineer or plumber will ensure precise results.
Key Components of Total System Head
TSH is determined by three primary factors:
- Static Head - The vertical height the pump must lift the water
- Pipe Friction Loss - The resistance created by pipes, bends, and fittings
- Velocity head - Energy required to maintain fluid velocity which is automatically calculated by the pump station selection tool.
Let’s explore how to identify and input each component.
Static Head
Static Head is the difference in height between the pump and the system’s highest point, typically the discharge location.
If Information is Specified
When the static head is specified on the plans, no calculations are required. You can directly input the static head height (excluding chamber depth) into the online calculator.
This information is often found:
- On the specification page
- In the layout plan
- In the legend
If Information is Not Specified
If the static head is not provided, you can calculate it using the site plan. To do so, determine the site elevation by looking for spot levels near the pump station and along the discharge pipework. For example, there’s a spot level of '99' near the pump station, and a spot level of '100.5' near the discharge location, it is clear the site rises in elevation by 1.5m. Alternatively, elevation may be marked as "FFL = 99" (Finished Floor Level). Use this to identify rises or falls in elevation along the discharge path.
Note: Only the site elevation needs to be entered into the online calculator; chamber depth is calculated by the selection tool.
Pipe Friction Loss
Pipe Friction Loss occurs as liquid moves through discharge pipes, bends, and fittings, creating resistance. This depends on pipe material, size, length and the velocity of water in the pipe, all of which will influence the overall TSH.
If Information is Specified
When pipe length, material and size are specified, enter this information into the selection tool.
These details can often be found:
- In the legend
- On the site layout plan
If Information is Not Specified
- Confirm Pipe Specifications:
· Consult with an engineer or plumber to determine pipe length, material and size
- Estimate Pipe Size:
· Use the online calculator to suggest a suitable pipe size and material based on the desired flow rate. If needed, refer to our blog “How to Calculate Flow Rate.”
- Measure Rising Main Length:
· Use a ruler to measure the discharge pipework length. Convert measurements to meters by using the scale located on the plan before entering them into the online tool. The scale typically looks like the below, including the sheet size, ratio and measurement size.
Need Further Assistance?
For more guidance on selecting your pump station, check out our other blogs:
- How to Calculate Sump Capacity
- How to Calculate Flow Rate of a Pump
- High and Low-Level Float Switches
If you have any further questions checkout our FAQ's or if you require assistance with your online pump station quotation, feel free to contact us.