Simple ET: How it Works, Setup and Best Practices

Simple ET automatically adjusts individual station runtimes each day according to the weather. You can enable Simple ET through a few basic steps. 

  1. To start, identify a global weather source for each controller. The global weather source  can be IQ™ Global Weather, a standard feature on IQ4.
  2. Under program settings, select Simple ET in the ET Adjust field. 
  3. Set a base runtime for each station. The base runtime should be chosen to properly irrigate during the highest average ET month of the year at the controller’s location. The highest average ET month is the hottest and driest month of the year.


 Simple ET Best Practices

  • During periods of low ETs, adjust the watering days pattern to not water as often. This prevents shallow watering.
  • Use Group Programming to set station base runtimes that are identical.
  • Simple ET uses a single start time. You cannot set multiple start times for your Simple ET-based programs.
  • Simple ET will provide a maximum of 300% of the base runtime(s).

Simple ET Adjusted Runtime Examples

These examples will walk you through Simple ET examples and calculation.

Simple ET Examples


View Examples

Simple ET Setup

Follow these steps to select the weather source and set base runtimes.

SImple ET Setup


View Setup

More training presentations are available under the Training tab on the IQ4 page.



What value does IQ4 use for the highest ET?  

IQ4 gets the monthly average ET for each month of the year from the weather source and uses the highest one for its calculation.

How does IQ4 select the program day cycle that matches my peak station runtimes?

Simple ET does not change day cycles, it only adjusts runtimes.

How does IQ4 calculate the station runtimes? What is the formula?

(current ET/highest monthly-average ET) X base runtime

What factors are included in the station base runtime calculation? 

The user determines the base runtime based on their experience and best judgment. 

How does current soil moisture balance affect how/when the program first runs? Should I water heavily or dry the site out before converting to IQ4 Simple ET?

Current soil moisture balance doesn’t affect anything at all. You should get the moisture exactly where you expect Simple ET to maintain it at the end of each irrigation cycle by watering at the same start time as planned for Simple ET. Switch to Simple ET and applications should match plant needs based on ET.

How does IQ4 calculate station Cycle + Soak™ times to prevent puddling and runoff with the single program start time?

IQ4 uses the Cycle + Soak time entered for each station no matter what starts a station (manual operations, automatic operations, etc.) It will use Cycle and Soak with the one start time.

How do I see what my programs are going to do (program end time, estimated total water, other)?

We are working on this feature. Dry Run will be available at the end of 2021.

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