The Irrigation Series, Part 3

by Rick Ellis

Welcome to The Irrigation Series, Part 3, my final installment! Today I explain how to best design your lawn irrigation system for optimal efficiency! To recap, my first post discusses why winter is the ideal time to plan your lawn and landscaping. In my second post, we learn why our lawn grasses need so much water to stay healthy and lush. The big scary word we used has the acronym ET (no, not Extraterrestrial). Our ET is Evapotranspiration, which is the combination of water loss from evaporation (water loss from the soil) and from transpiration (water loss from the plant leaves). Irrigation is simply replenishing the water lost from ET that is insufficiently provided by Mother Nature.

The Five Common Lawn Misconceptions 

To design an optimal lawn irrigation system, let’s address the five common lawn misconceptions I’ve encountered throughout my career. 

The more you water, the healthier your grass will be
Ultimately, over-watered lawns produce a yard full of mushrooms and other fungal infestations. Many people do not appreciate these additions to their lawns. Rather, most lawns need about an inch of rain a week during the summer heat. This includes all sources, so you need a way to determine how much water you’ve had since the previous irrigation. That is what “smart controllers” are for.  

lush grass house in background the irrigation series part 3

Nighttime is a perfectly fine time to water 
This relates to my first point as watering at night tends to lead to overwatering, thus promoting the growth of fungi and other scary things with weird Latin names. Ideally, a yard should be watered in the morning before sunrise and the initiation of ET.  

A typical residential irrigation system uses about 200 gallons of water per week.  
This is also false. The average yard has 6 irrigation heads per zone and 6 zones. The output from each irrigation head averages around 2.5 gallons per minute (gpm). Some quick calculations demonstrate if you schedule your irrigation system to run 30 minutes per zone – 2.5 gpm x 6 heads x 6 zones x 30 minutes – you will use 2,700 gallons in ONE day’s irrigation cycle, and 5,100 gallons average per week! This also contributes to a large, unnecessary water bill! 

My irrigation clock works just fine – there is no need to upgrade to a new “smart” controller.  
Properly managing your lawn’s irrigation needs without a smart controller requires a rain gauge and soil sensor, as well as operating each zone using your own effort and calculations for 24 weeks (the average irrigation season length in the Metro). Many of us do not desire to do all this extra work when it is simply unnecessary. Trading out the control clock (a mechanical clock with manually timed settings) for a Wi-Fi enabled, weather-based controller is a huge change. Once properly programmed, (and maintained with a simple yard audit by a Certified Landscape Irrigation Auditor), you can expect on average a 30- to 55-percent water reduction for the season! Much of the savings occurs in the spring and fall when temperatures and the ET is lower; however, your irrigation distribution and efficiencies will improve with a more healthy and beautiful lawn.  

It is best to irrigate once a week but irrigate for a long period of time (typically 45 minutes or more). 
Although you may be irrigating less than the average person with this technique, when the ET is low, such as chilly days in spring and fall, you will still be overwatering. Also, during the heat of summer, having a week in between watering may be too long. This will stress the lawn if it doesn’t rain. However, the main reason this method is not the best is because of runoff. What happens when you pour water onto hard dry soil? That’s right, it “runs off” the soil. When dry, it takes time for the hard soil to moisten up enough to increase the permeability of the soil.  

There is a Solution!

A smart controller is an easy way to address these common issues. When programmed to “cycle and soak,the controller is set with two or three shorter “on” cycles. Additionally, the cycles are set with enough time in between for the soil to soften and allow more complete infiltration. This technique is mandatory for clay soil or sloped yards; however, it can be used in any zone. This way, runoff is minimized and more water gets to the roots over a shorter amount of time. 

And with that, The Irrigation Series comes to its conclusion. 

I hope this information has been educational and that your lawn and landscape are at their healthiest this summer! And just in case you missed them, click here to read posts 1 and 2 of The Irrigation Series! 

 Thanks for reading! See ya soon! 

wet grass irrigation series part 3

Rick is a professional hydrogeologist, Certified Landscape Irrigation Auditor, and operates an irrigation and water conservation company in Woodbury, MN called Save Water Inc. A father of two, Rick loves spending his free time exploring small towns, playing golf, and teaching folks about water-related topics. Please reach out to Rick through his web page to learn more!