Size the Mainline Manually Using Caps
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Size the Mainline Manually Using Caps


You have a specific diameter of mainline pipe in mind for your system design, and you need to size the mainline manually. That is, you want the mainline size to be bigger or smaller coming from the meter than the diameter our Size Mainline tool is assigning to it.


For example, you might have a 2-inch meter and the system is sizing for a 1.5-inch mainline coming out, but the client wants to see a 2-inch mainline coming from the meter.

Our Size Mainline tool is demand-based. That is, it requires a demand in order to generate a requisite size for the pipe. However, many irrigation designers know beforehand that they want a certain size mainline – often from many years of valid experience. In terms of our software, it's absolutely fine to size the mainline manually in this way. You'll just need to validate the hydraulics that call for your desired size.



To size the mainline manually, you'll need to invent a demand that will force the mainline to have the diameter you want to use.The system will validate the hydraulics and generate extremely accurate pressure loss calculations.

This method is also the easiest way to validate our software's pipe sizing calculations.



Here's how to achieve your desired mainline diameter using pipe caps:


1. Add and place a pipe cap from our Auxiliary Equipment database, making sure to configure the cap so it has your desired demand and results in your desired pipe size. You can place a plot or non-plot cap.

Assigning your desired demands to caps in your system will allow the software to calculate the pressure loss. It also gives you the ability to finesse the entire system by nothing more than editing the demands at each cap and altering the overall velocity.

Do not place the cap on an existing valve station. Doing so would create a false critical station, which would cause problems with your system's hydraulics calculations.


2. Draw mainline pipe connecting the cap to your water source.


3. Size the mainline using our Size Mainline tool.


4. Use our Edit Equipment tool to see the given flow and pressure at any given segment of pipe.


5. (if necessary) If you're not getting the results you're looking for, edit the cap and adjust its flow. Then size the mainline again. Repeat this step until the mainline sizes how you wish.

If you're the style of designer who likes to lay out mainline first (which we recommend in many instances), just note that you can drop in a few caps at key locations – maybe at each building complex, sports field, community, etc. You can then connect the caps and size the mainline.

Caps can come in extremely handy within system designs that need to account for future demands and/or existing layouts. For more information, please see our documentation sections on:

Last modified on May 27, 2022


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