That's a lot of water to throw down

I’m starting up my system here in CO. We’ve had a pretty wet spring so far and have not needed irrigation, yet.
I have watering restrictions to MWF only, so I have chosen a fixed schedule. In addition I chose only M & F to water in this early season. I’ll move to MWF as it warms up. I updated my nozzle inches per hour (.4) according to Hunter’s specs for rotary heads. I also updated my soil type (loamy sand) and available water (.07) according to Web Soil Survey.

Example of one zone

When I set up the new fixed schedule, the suggested run time is 2h 2m per zone in full sun & 1h 1m for the one zone in mostly shade.

If the inches/hr is .4, then it seems this is suggesting one inch of water twice a week. This is excessive and, in my opinion, irresponsible for a drought prone west.

Am I misreading something? Or do I have my settings wonky? Is there something else you need to see to make a determination?

Thanks for the advice!


Hi Jason,

Those are both pretty big levers that will increase watering. We almost recommend double in/hr for our rotary head default setting at .7 in/hr.

Available water is another one. Putting that back to the default .2 should make a pretty big difference.

Thanks for the suggestions, Chris. I’m clearly no expert here, but do enjoy nerding out on the numbers from time to time, researching details, and learning something new. I’m happy to return those back to recommended settings to get the better outcomes.
It is confusing, as an armchair water manager, to input the correct data (according to the nozzle manufacturer & an official soil survey), only get undesirable results. Seems that either my data was wrong or the way its handled is missing something. Or is there something else I’m not accounting for? Maybe a math problem way above my head?
On a different note, it is encouraging to have a Co-Founder remain in close contact with the customers. Kudos for keeping your finger on the pulse.

Thanks Jason!

With regard to inputing the data correctly: I think you can go ahead and try Hunter’s recommendation for in/hr. Maybe just keep an eye on it for overwatering. It’s just saying that a very low amount of water is coming out of those heads.

Available Water is kind of a tricky variable and is super sensitive; serious optimization here. You would want to be really sure and dialed in on your soil to make that change. Since soil is so variable, I would just keep that as is. But that’s my 2 cents :slight_smile:

I’m not as familiar with how the Fixed schedule calculates water output, but the factors of 0.07 Available water, 5.91" root depth and 50% allowed depletion would calculate to about 0.2" of water for a Flex Daily schedule. From what I’ve seen, Fixed schedules usually come close to that.

And using that 0.2" of water and even with the low value of 0.4" Nozzle Inches per Hour, that would only give 35 minutes of watering including efficiency (but not any sun factors), certainly not 2 hours+. I have to admit, the time numbers don’t seem right.

chris isn’t 0.2 available water high for sandy soil? And wouldn’t that increase the water applied at once?

@rraisley I can report that editing those 2 parameters as suggested by Chris brought the watering time down to 3h 10m total.

Good call @rraisley and I misread the above. @jbhco I thought you were adjusting available water directly in advanced settings. I see now that you selected loamy sand for the zone setup menu, which would make the available water .07 in/in by default.

As @rraisley said, 2hr+ 3 times a week does seem unusually high, especially for this time of year. We’re happy to take a look at things on our end if you want to private message me the email you used for your account — your call of course.

A few things I would recommend:

  • If you’re going to keep loamy sand as your setting, I would set available water back to .07
  • If you want to push available water back up, I’d choose a different soil type to keep things system driven

I would say that if you’re going to stick with sandy loam keep on eye on your watering. That would be a somewhat unusual soil type for CO and we’re happy to take a look at that as well, understanding that you got that from Web Soil Survey of course.

Let us know, we’re happy to help!

What Hunter sprinklers do you have?

@tmcgahey Hunter MP Rotators

I have these too and love them. I’ve found on every location that I have these installed, they put out a bit more than the Hunter spec sheets. It could be based on the fact that I converted traditional spray nozzles to the MP’s, and I might have a bit more overlap than a “perfect” installation, but I see .55"-.65"/hour while doing a catch cup test.

@chris You were right. I was adjusting Available Water directly in advance settings. I did this based on data from the Web Soil Survey detailed in this post and promoted in the original post of this community thread. I also chose loamy sand based on the same data and nozzle in/hr based on specs from the Hunter website.
In addition I chose to water only 2x per week (M,F) for right now (instead of my allowed 3x/wk - MWF) based on recommendations form local landscapers. I will increase the frequency to 3x/wk likely in July.

Ok cool. Well let me know if you’d like any more help from us. Happy to assist.

@tmcgahey Good to know your experience with those. I also have PRS40 spray bodies all around to regulate the pressure to 40PSI for each nozzle. So, I think I should be pretty close to Hunter specs, but have not done a catch cup test, yet.

Good call on the PRS40’s. I don’t have those, but I have my system dialed into about 41-44psi, so I’m pretty close.