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I Can't Size the Mainline! (Mainline Sizing Troubleshooting)


You are unable to size the mainline pipe in your irrigation system design.


Causes & Solutions

This is a common issue that is typically caused by an error in your drawing and not by the software itself.

Here are some common examples and solutions:


"Unable to size system" error message

You might see an error message stating Unable to size system. If so, see our Unable to size system (Unsizable system) article for the solution.


Valves already piped

The most common cause of error when trying to size the mainline is when a user copies valves that were already piped. When this happens, both copies of the valve think they are connected to the same pipe. This results in a nearly infinite number of mainline loops. So do not copy Valves and Pipes. Instead, place them.


Mainline pipe "exploded"

If you have used the Explode command on all the Mainline pipe, it reverts the pipes to Line objects. In this case, you will need to redraw the mainline, and take care to not Explode any Land F/X objects.


Issue with the Shut-Off Valve Directly After the Point of Connection (POC)

Sometimes there is a piping irregularity with the shut-off valve right after the POC. If you use our Highlight Station tool and select the POC, you can see that it highlights only to that valve. And if you select any mainline downstream of the Master Valve, it will highlight everything, but only back to that shut-off valve – not the POC.

To fix, you can just delete the mainline pipe segments between the POC and the master valve, and then repipe those.


You're trying to size the mainline, but the system is not recognizing the booster pump

If you use the Equip Info button and select that one segment, you'll see it is still unsized. So the system is not recognizing that segment as it sizes this system. It would suggest a piping error – specifically, indicating that a segment of pipe that is not connected.


In this case, you will need to delete a segment of pipe so that the system is not looped, and then to use the Highlight Station button to see what is still connected. In this fashion, you could determine which segments need to be redrawn.


Multiple water flows

The system can only deal with one water source at a time. If you intend to have multiple meters running at the same time, you will need to create a Custom POC, with the demands of the two combined meters, and size the mainline using that.

When You Try to Size the Mainline, the Drawing Freezes During the "Recursing Pipe" Process

If you're experiencing this issue, see our Sizing Mainline: Drawing Freezes During "Recursing Pipe" page.


The pressure required for your valves is extremely high

You may be simply seeing required pressure rates for your valves (or drip valves) that are much too high for the rate you've set for the service line.


For example, let's say you've set the service line to 65 PSI and are proposing 25 PSI drip assemblies, and you're somehow losing 18.92 PSI though the valve. But then, when you hand clculate, it appears that you should have 33.79 PSI at the mainline before the valve, then lose lose 3 PSI through the valve (putting you at a bit over 30 PSI), and then the regulator on the assembly drops the pressure to 25 and the system should work just fine. So what's the deal?


In this case, the valve loss is due to the amount of flow you've set to that valve. To verify, look at the charts for that exact valve model and you'll see the required inlet pressure to run at the given reduced pressure. That difference is considered the valve loss.


If you're losing that much pressure, it's because the design of that particular equipment results in that pressure difference.


Your options in this case include:

  • Selecting a different manufacturer's valve to use in this project
  • If it's a drip valve, you can also choose to put a regular valve in its place and note the need of a filter or pressure regulator in conjunction with the standard valve.

We understand the potential frustration in wanting (or being required) to use a particular valve, or manufacturer, only to find that the valve in question comes with this level of potential pressure difference. Unfortunately, it's an issue that's tied to the design of that particular valve – not to the software. It's also one of the conditions for using pressure regulation equipment.


Want to learn more about pressure regulation and the necessary equipment, see our Understanding pressure regulation webinar, presented by Kelsey Jacquard of Hunter Industries.

Last modified on Oct 01, 2018


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