Drip Emitter Calculator for Precipitation Rate & Area

@franz one of these days I’ll teach you all of my community secrets :upside_down_face:


I don’t come back to this often at all…the excel file is saved on my desktop! :stuck_out_tongue_winking_eye:


Hi there. First off, great resource, being in AZ this is helpful.
One question I have, is the system I have inherited has many of those micro bubblers, which I believe are 0-10gph and a few others that are more unknown. Would you recommend switching to straight GPH emitters? Many of the plants in my yard are doing great but I would love to get this even better!

Also, citrus, how do you manage those? Thats the zone I am having the hardest getting dialed in.

I treat palms like trees, is that correct?

One additional question, Im confused on the spreadsheet.
In one zone, lets say I have 4 trees, canopies of 6,6,8,10 and 3 shrubs, canopies of 3, 6, 6.
Gallons needed for each is then 26,26,38,59 and 8,20,20

How do I figure out what to put into each cell, GPH per plant and Gallons per cycle, since its all under one Flex Daily inches amount.

Firstly, welcome @apsmith12!
If you post a bit more info about the trees, we could offer specific suggestions. What type of citrus? Are they mature trees? Are they in a lawn or on their own zone? Type of soil?
I have three mature trees–a Meyer lemon, an “AZ Sweets” orange and Lisbon lemon. During the hottest part of the summer, I deep water the orange and lemon every 7 - 14 days. During the winter, I may irrigate them once a month. The soil needs to dry to a depth of about six inches before the next time it’s irrigated.
The Meyer is in a pot, so it gets watered more often. My trees are happy with that schedule and produce well. I had so many lemons this year, I had trouble giving them away. I considered leaving grocery sacks full of lemons on the neighbors’ door steps, ringing the bell and running. :smile:


So I have 7 zones, but for simplicity lets focus on my citrus zone.
Per the graphs my yard is cut into what looks like .05 and .09 available water, but lets stick with .09. I still think there needs to be some compensation there for added soil / mixed soil, its not like it was planted in pure gravely loam.
This zone has 5 trees, 1 establish (also that I dont care for) and 4 new.
Hybrid Sweet Orange/Bitter Orange ~6ft
Lisbon Lemon ~3ft
Key Lime ~ 2ft
Clementine ~2 ft
Valencia Orange ~2ft

The lemon is struggling (too dry I think) which is what got me back into my Rachio settings. The rest of my yard is actually looking fairly good, either by chance or luck. The other zones are either grass or some mixed types, so Ill leave those for later. I should note much of the yard is utilizing the adjustable micro bubble style heads (0-10gph)

The grass is easy, and as I have read, we are all aware GPH vs in/hr is the main issue with drip calculation, but I cant see how the formulas you have on these forums / excel sheet actually work outside of very uniform situations.

If I understand correctly, by setting the soil type, root depth and available water, Rachio has all it needs to determine how many inches of water it needs to drop. Changing the emitter type after that doesn’t change anything but how long it runs to drop that.

Now if I have some 2GPH emitters and some 1GPH emitters, then I dont see how the in/hr could be just one single number in the app, so I assume its necessary to have all of the drippers on a single valve the same size, and only adjust how many.

That then brings the problem of the smaller trees only needing 1-2 drippers but the one large tree needing far more to compensate for the blended runtime to cover the wide range of gallons needed using only 1 size dripper.

I can see where your situation would have you looking at your settings.

Gardening is both art and science. Rachio has the science down pat. There is no one size fits all and so many variables, no controller can accommodate all, but Rachio does an amazing job if the right parameters are used. The art of gardening is an on-going learning opportunity involving plant cultivation techniques, and even though I’ve been gardening for years, I am still learning.

I use both fixed and flexible zones. I agree, the grass is easy. The flexible schedules are perfect for that and a shaded zone I have that has a ground cover.

When it comes to the drip system, I use fixed schedules and knowledge of the water requirements for the types of plants I have growing. Some of my established desert plants thrive only on the rain we receive. (Unless it’s a particularly dry year)

It’s not a good idea to mix emitters with different flow rates, and as you noted, more emitters could be added to plants that need more water.

According to the U of A Cooperative Extension service, “Water use for grapefruit and lemon is about 20 percent higher than that of oranges” I would use a fixed schedule for those young citrus trees to get them through the heat of summer and water according to the needs of the lemon. The diameter of the canopy and time of year will determine how much water is needed. Mulching those young trees is also a good idea. After the trees are well established, a different type of schedule could be considered.


It’s not a good idea to mix emitters with different flow rates, and as you noted, more emitters could be added to plants that need more water.

I dont actually agree with this. I think in the context of a flex scheduling and calculating in/hr this is true, but on a fixed schedule, if a tree needs 2x the water, either have 2x the emitters, or same number of emitters at half the size.

Now using a fixed schedule, I get your logic, but it almost feels like its not taking advantage of the Rachio? I think my struggle is to do the work outside of the system.

Thank you so much. This is something Rachio should have done. That said, I do really like my Rachio3, but been very frustrated with this whole GPH conversion stuff

Yes, it has been a bit of a frustration. If there were an in-app purchase or an app subscription to gain access to an integrated GPH calculator for those of us that have zones on drip or micro sprayers… would love to support Rachio somehow since I don’t maintain a lawn.

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After a good night sleep, this morning with a cup of coffee, I took a good look at your spreadsheet. Love it. Do have one question though. In the input table, under the “GPH per plant”, what do you suggest that I enter if my trees for example, are not all receiving the same GPH? I have some very young ones that I have two 1GPH emitters under and some trees have three 2GPH under them. Do you suggest I take an average across all my trees and enter that average GPH in your first column?

Yes, totally agree with you.

Registered just to say thank you @azdavidr for putting this together. I’ve struggled with emitters for a long time and finally just decided to dig in and really calculate these numbers using the spreadsheet, and everything looks great. The only thing I noticed different with my Rachio 3 is that you don’t create a custom nozzle, you just set the in/h measurement in the advanced settings for the zone.

Also I had the same problem as @BiebsAZ in that my flex daily showed 0’s, but then I realized I needed to create my flex daily schedule and then let it run at least once and then the numbers showed up. All minor things though. Thanks again!

Great, I’m glad it was helpful! I finally got fed up trying to figure out the in/hr to gph thing and just sat down with my pencil and calculator. It’s nice to see that it’s helping others. Flex Daily is a great way to irrigate on drip, so it’s worth a bit of extra effort in my opinion.

Good point. I wrote that doc. a while ago now!

Thanks again for the nice note of thanks @bksaville !!

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I was struggling to find a way to convert my dripping emitters to inch/hr precipitation rate. I found this article: Calculation of Precipitation Rate (PR) of Drip Emitters and Bubblers ...
Conceptually, PR = gph / root_area for one tree. For root area, maybe critical root area can be used? What is the Critical Root Zone around a tree?
I feel this is an intuitive way to calculate PR. Of course, root area is a little hard to get right.