I’m sure there are countless posts on this, but needed my own discussion.
I have 4 drip zones, with around 10-20 plants per drip zone. I try to do rain bird red 2gph drippers with 1 on each plant. Each zone is a mix of bougainvilla, yellow bells, cape honeysuckle, and lantana. I have 2 zones in front and 2 in rear. I calculated 1.125 gph out of a single emitter, even though they are rain bird 2gph red. My plants are established so i calculated 2 ft x 2 ft for area per plant.
Soil is mostly clay, I did the jar separation test and I had about 1% sand, 1% silt, 95% clay, and 3% water or so. It was very much clay.
For some reason when i do flex daily, it gives me a 1 hour run time. It appears to actually not be enough because my plants get wilted. I do not have any real advanced settings on my 4 zones, and they seem to run 1 hour 11 minutes with the default settings.
Should I go in and set the exact square footage, the crop coefficient etc? I believe the available water at 0.15 is correct, root depth is 15 inches, all default though.
Where in North Phoenix are you (SE Gilbert here…)? That seems like and AWEFULLY high clay concentration for Arizona.
This thread is the BEST for calculating the drip settings. If you follow the directions, you should be able to get a PR (in/hr) that works well. Main thing to start with is dialing in your soil though, and again, I struggle with that clay content for the valley.
For reference, here are my old settings from when I set mine up. I have 1gph emitters on my shrubs, which equates to a .30 in/hr, which has my shrub zone running for right at 4h each time, but this is based of my clay loam soil (not to be confused with heavy clay).
Square footage does nothing other than calculate estimated water usage, nothing related to actual watering. 15" might be a tad deep for anything but the most established and strong shrubs. I have mine set at 12" right now, but I have a mix of well established and newer planting shrubs, and you need to cater to the more needy.
Thank you. I also realized through some of my notifications I started this process back in 2018 and kind of gave up.
I was using AI to help me calculate some of this and after testing 1 nozzle I’m getting 1.125 gallon per hour, per emitter. Using the AI math (I’ll try this spread sheet next) it was suggesting my PR was 27.05? I am in anthem and my soil map shows 12 and 44. I am in 12, and 44 is within half mile around me in all directions.
|12|Carefree cobbly clay loam, 1 to 8 percent slopes|181.9|43.5%|
|44|Ebon very gravelly loam, 1 to 8 percent slopes|201.0|48.1%|
From AI about my PR:
Step 2: Relate Output to Soil and Root Depth
The goal isn’t to dump 12 inches of water depth across the zone in 3 minutes—that’s not how drip irrigation works. Instead, we’re delivering a small volume of water (e.g., 7.2 oz per plant) to the 2 ft × 2 ft root zone, letting it soak into the clay soil to reach the 12-inch root depth over time. Here’s how:
Volume to Inches: Convert the water applied to an equivalent “precipitation depth” over the area.
Yea, that PR math doesn’t check out…at least not in this application.
If you follow the spreadsheet, it is using the inches of water Rachio calculates it needs to put down, the gph of your emitter, and the amount of gallons you should put down (from the "Water Use it Wisely guide) to calculate what the PR should be set to.
Were you able to check the soil type? I did find an error in my zones, they were bubbler, i changed to emitter. Now my drip is scheduled to run for almost 2 hours. That seems more in line with 2-4 gallons per plant per watering, while doing 1.125 gallons per hour from my emitters.
You can use the Web Soil Survey site to look up your address and would tell you what the native soil is. It is usually pretty accurate, however with large subdivisions, they do a lot of earthwork to the lots prior to building, so use it as a rule of thumb. What you found from AI might be somewhat accurate since it probably pulls from the WSS site…
Not sure what your shrubs look like, but I usually set mine to put down about 4 gallons. My biggest “shrubs” I have stepped up to a 2gph to give them a little extra if it looks like the 4 gallons (which works on 90% of my shrubs) isn’t cutting it.
Here’s what I ended up with in Rachio after setting up soil. It’s .84 inches in the app, which breaks down to .32 PR? Hopefully that makes sense. It appears the run time is 1 hour 40 minutes per zone.
Yep it looks like AI was doing GPH instead of GPM in its math. I think changing from bubblers to emitters was the biggest help as that doubled my drip time. Now to watch the water bill.
I’ve spent a few days thinking about this and I think I’ve figured out the mistake I’ve been making all these years. Rachio default for emitters is .5 nozzle inches per hour. I think the spread sheet is designed to take your GPH and convert it to a more accurate nozzle inches per hour based on the soil type?
For my example, soil is .14 available water, 12 inches of root, clay soil, and 100% efficiency. This causes the application to output each watering is .84 inches. My run time is 1 hour, 40 minutes.
In the spreadsheet I fill out that I have 2 gph emitter, I want 4 gallons of water per plant, and the inches of water applied from the Rachio application which is .84. The spreadsheet output is now saying my custom nozzle PR is .42. So the spreadsheet is basically reverse engineering the soil types and the Rachio .5 nozzle inches to determine how to put down 4 gallons per plant?
So first, is my new lightbulb moment accurate, in that I need to adjust the nozzle inches per hour per the spreadsheet to get 4 gallons of water, for 2gph emitters, and just let the time of the run hours adjust based on that? And secondly why do we have to reverse engineer the watering inches, could Rachio simply take our 2gph emitter and estimate the nozzle PR within the app in some manner themselves?
Not quite. What the sheet is doing is taking what Rachio algorithms say it needs to put down in a single run (inches of water) and convers your nozzle gph to fill that inches of water need.
For example, based on the settings I have for my tree zones (plant type, root depth, soil, etc), the algorithms say I need to put down 1.95" of water each time. @azdavidr built that sheet and can maybe give more detail as to what the calculations are, but it basically takes my GPH (I have multiple 2gph emitters per tree) and the gallons you need to apply (based on Water Use it Wisely site) to calculate what the nozzle PR should be set to.
Why that calculation can’t be just added to Rachio (include your GPH per plant and estimated gallons needed per plant) to calculate the PR for you, that would be a question for @franz .
The calculation just takes gal/hr * inches-of-water and divides it by the total number of gallons you want to deliver in a cycle. If you work out the units it’s:
Just to clarify, I should be using the spreadsheet “inches per hour” from column H within my rachio zone, advanced settings, nozzle inches per hour? Since I know my inches of water in flex daily schedule is .84, and I want 4 gallons deployed per plant, with 2 gph per plant? So I should have .42 custom PR on my nozzles?
I’m getting closer, just want to make sure I get all the important static information set, and then I can adjust other items like coefficient.
Yes. Once you enter the “Inches of Water applied in Flex Daily schedule” value from Rachio (found in your “moisture levels” under irrigation), and the estimated gallons (from the water use it wisely chart), and the emitter output GPH (add together total output if multipler emitters per plant), the calculation in column H will be what you want to enter for inches per hour in the zone settings.
You mention making changes afterward. Beware that depending on what you change, you might end up changing the value of inches of water that Rachio calculates, which may require you to run through the spreadsheet again.
Yes I’ve left most of my settings for default for years because I didn’t deep dive into how rachio calculated the nozzle output. Then I started thinking about oh I could possibly have 1gph, 2gph, and 5gph nozzles how does rachio know? So I started focusing on setting the important information like soil quality, and plant type, and then I can fine tune it.
I have a very simple system. 2 zones front landscape drip with bushes, 2 zones rear landscape with bushes, and 3 zones of back grass. I figured drip was the easiest to learn since its all 2gph per plant, with 10-15 of the same types of plant in each zone. orange jubilee, green hopseed, bougonvillea, and normal desert landscape flowers like that.
