Determining the correct pump size for an irrigation system is crucial for optimal performance and efficiency. The required pump size isn't a single fixed value; it depends directly on the specific needs of your irrigation system, primarily the total water flow (GPM) and pressure (PSI) required.
How to Calculate Your Irrigation Pump Size Requirements
To find the right pump, you must first calculate your system's water flow requirement. Based on common methods, a key step involves assessing the demand of your sprinkler heads.
According to one approach, you should:
- Determine the number of heads in your irrigation zone or system that will operate simultaneously.
- Multiply them by 3. This sum represents your estimated Gallons Per Minute (GPM) requirement for that zone or system.
Example: If you have 10 sprinkler heads operating in a zone, your estimated GPM requirement would be 10 heads * 3 GPM/head = 30 GPM.
This calculated GPM requirement is then used to select a suitable pump. You should compare this GPM requirement with the pump performance chart found on the pump carton.
Key Factors for Pump Selection
Once you have your GPM requirement, you need to consider pressure and suction lift:
- Pressure Requirement: The pump must be able to deliver your required GPM at the necessary operating pressure for your sprinklers. The reference specifies performing at 30 psi. Sprinkler types vary in their optimal pressure ranges, so verify this for your specific heads.
- Suction Lift: This is the vertical distance the pump has to lift water from the source (like a well or pond) to the pump impeller. A higher suction lift reduces a pump's available pressure and flow rate. You need to find a pump that can deliver your required GPM at the specified pressure (e.g., 30 psi) while also accounting for your determined suction lift distance.
Using the Pump Performance Chart
Pump performance charts (or curves) are essential tools. They show how a pump performs under different conditions, specifically demonstrating the relationship between:
- Flow rate (GPM)
- Total Head (which relates to pressure and vertical lift)
- Suction Lift
You use your calculated GPM requirement and your system's total head requirement (pressure needed at the sprinklers plus elevation changes and friction loss, considering suction lift) to find a pump on the chart that meets or exceeds these numbers efficiently.
Summary of the Sizing Process
| Step | Action | Output |
|---|---|---|
| Calculate GPM Requirement | Count simultaneous heads & multiply by 3. | Required GPM |
| Determine System Pressure | Identify operating pressure needed (e.g., 30 psi). | Required Pressure (PSI) |
| Measure Suction Lift | Measure vertical distance from water source to pump. | Suction Lift |
| Consult Performance Chart | Compare your GPM, Pressure, and Suction Lift needs against pump data. | Potential Pump Models |
| Select Pump | Choose a pump that reliably delivers your required GPM at the necessary pressure and suction lift. | Correct Pump Size (e.g., HP rating) |
By following these steps and using the pump's performance chart, you can find the pump that will deliver your gpm requirement at the suction lift distance determined performing at 30 psi, thereby determining what size sprinkler pump you need.
Understanding your system's exact flow and pressure demands is the most accurate way to select the appropriately sized pump.
