Struggling to get settings right for drip

My drip is set at 0.4”/hour. It’s not exact with some getting more and some less due to small shrubs and big trees being on the same zone.

@dane, back in 2016 the community had a long discussion that included @emil on the problems with single point irrigation and the way Rachio was recommending to set the nozzle in/hour. That discussion seems to have been forgotten over time.

See:Gathered data, need help figuring out drip custom nozzle rate

I have read that thread a few times; and still don’t understand where it ended up. Emil’s recommendation lead to watering of a few minutes, putting cups of water in the ground rather than gallons.

Look, here’s the thing; let’s make this simpler — say I have a 5ft diameter tree and a 10ft diameter tree on the same zone. Both using same plant factor.

Formula implemented at Landscape Water Requirement Calculators - Center for Landscape & Urban Horticulture

At average ETO 0.15
(Tree A) 5ft diameter tree : 6.43 gal/week
(Tree B) 10ft diameter tree : 25.70 gal/week

I have ZERO problem setting up emitters so that Tree B has 4x the output per hour than Tree A. Let’s say I put 3x2gph on A and 12x2gph on B. Close enough. One hour provides approx a week of water when ETO is 0.15. I could do that via a manual schedule.

BUT what about when ETO gets to 0.20 or 0.25 or more during the summer? Isn’t this what Flex Schedules are supposed to solve —- water more when the weather (hence ET) is higher? Rachio knows the ET and can calculate how much water is in the ground; what I don’t have is a way to convert the point gph into inches for the precipitation rate (in this case it’s calibrated for 1hr=ETO .15).

I won’t even claim to understand what the square foot measurement is supposed to be in such a scenario….

In short, I’m willing to do the math to make each plant in the zone uniform so that there’s a single calculation ratio between trees (making a reference tree, effectively) , but I still need Rachio to dispense that amount of water and know when the ground is dry.

I THINK this is how it should go down:

  1. Get regular zone settings match the zone as close as possible
  2. Now you have some initial values for root depth, Crop Coefficient, Allowed Depletion, etc. in Advanced
  3. This also results in Rachio calculating a certain watering duration for the zone

Now there are two options

  1. given the duration install enough emitters to apply the expected number of gallons (say as given to you by the calculator) at the current ETo
  2. given existing emitters (number of flow rate) fudge Nozzle Inches per Hour to end up with the right number of gallons applied per watering.

Now the $1M question is: as daily ET changes will Rachio’s calculation match expected gallons or not. If it will, all’s good. If it won’t, then I will claim again that Rachio doesn’t work with drip. And this time I’m not going to claim that it’s just the UI.

I am planning to try this approach over the next several weeks. If you want to try it as well, please come back and share your results.

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IMHO, not system, especially Rachio’s, can deliver the right amount of water out of the box without some sort of calibration. People complain that Rachio is complicated, because they’ve been told in the past just to water every zone 20 minutes every other day or some such. And if you take all those recommendations, they vary more widely than Rachio’s recommendations. But without knowing how much water is being applied for a given time, no system can come up with decent calculations.

Again IMHO, part of the setup process for Rachio should include a test run of each zone, with water meter readings before and after. Entering that information into Rachio would give it GPM/GPH which is a great start. After this is done (and it wouldn’t take long, just measuring water use - not like the PIA catch cups), knowing the Area of a zone gives you everything you need to accurately water. For Drip systems, since again, you already know the water flow, entering in the water requirements for each zone (counting number & size of trees/shrubs would be a great way) again gives Rachio everything it needs to know to calculate times.

Area is easy to calculate in some yards, and using the Rachio app to measure it works great. And people can count trees. With this information, I think we’d be 90% there. Without it, we’re nowhere.


Idealism and new features aside; how do we solve for the current problem given the scenario I’ve layed out?

Hi @rizzyk, I’m a data scientist working on some concepts for how we can support single-point irrigation using drip systems and emitters, i.e. all the problems discussed in this thread. I’m going to help you find some settings that will work for your problem, and provide some background. This is long winded but unfortunately it is quite a complex topic (one we are hoping to make much simpler!).

The community has rightly pointed out that the Rachio interface and conceptual model was designed and built for solving lawn irrigation and related types of zones which can be generally parameterized by the et demands of the crop and the watering output of the system in linear units (e.g. in/hr). This system is area-agnostic because we assume that sprinklers are distributing water evenly across their zones, and then provide the efficiency parameter to account for system waste. This is the way the ag and irrigation industries typically calculate watering, and it’s a good system for calculating irrigation according to weather, where the fluxes (et, precip) are all in linear units. However customers here are rightly pointing out that both the emitter hardware and the available info for watering trees etc are often strictly in volume per time. The way our system currently works, you basically need to find a linear nozzle rate that meets the volume/time application rate of the emitters, which usually requires some manual tuning.

OK, so let’s try to set up your zones so you can tune them. You have your hardware dialed, so we just need to get the software parameterized right.

  • set efficiency at 100%. Drip systems don’t really have waste. Efficiency <100% will add runtime to compensate for waste.

  • zone area will not matter

  • I would start with the defaults for available water and root zone depth. 16% is reasonable for a compact soil you have re-worked. For most soils it is a little less than the bulk porosity, but compaction history and clay complicate this. Root zone depth default for trees is 25 inches. These and managed allowed depletion (a unitless fraction) combine to create the “allowed depletion” parameter. This is essentially the “size of the bucket” we will try to fill. It will affect BOTH duration and frequency, so tuning it can have complex results.

  • The two knobs you want to play with are crop coefficient and nozzle rate. Crop coefficient will determine your zone’s sensitivity to ET demand, and nozzle rate will throttle your runtimes.

  • For crop coefficient, we set trees at a 0.75 default (75% of daily reference ETo). The higher the crop coefficient, the more quickly our system will estimate that your soil has dried out, which will trigger another watering. If you want to water more frequently, try increasing in increments of 0.1, and visa-versa.

  • Nozzle rate: this is the tricky one. I agree it is an obscure process trying to get from a volume rate to a linear rate. There are many resources offering calculators and tables to do this conversion, some use area, some use the linear length of the drip tubing, and some use neither, so it can be confusing. I’ll append some below.

  • With this in mind, there are really two ways to approach the nozzle rate question: calculate it from first principles and trust that runtime OR start with a target runtime and tune until you reach it.

1st approach: elegant from an engineering perspective, but you need to make measurements to be accurate. Emitter valves will often have a published flow rate (e.g. 4 gal/hour) but this is for an “average” water pressure. To dial this in, you need to measure the flow rate at your pressure using a measuring cup and a timer. Once you’ve calculated gallons per hour, you can convert to a linear application rate using a conversion table, assuming 1 ft2 of area per emitter (common, but not always accurate):

  • 1.6 in/hr = 1.0 gph/ft²
  • 1.44 in/hr = 0.9 gph/ft²
  • 0.96 in/hr = 0.6 gph/ft²
  • 0.64 in/hr = 0.4 gph/ft²

So that requires some on-site measurement and some assumptions about the application area. That can be measured too, but it’s hard. I’m personally surprised how often this detail is hand-waved over, even by the state of CA in their water use calculations for residential irrigation. So there is some uncertainty.

The 2nd approach is to use heuristics about the runtime for trees, like the UCANR equations you used to derive 6.43 gal/week and 25.7 gal/week @ ETo = 0.15 inches for trees A and B, and experiment to find a good application rate. Use your emitter flow rates to calculate runtime per week (again, measuring these rates will give you the best results), then, in month with average ETo = 0.15 and with all other Rachio advanced settings constant, vary the nozzle rate until you reach that runtime. If you need to get more waterings in a week for the runtimes to be reasonable, tune frequency with crop coefficient, within reason. You can then keep that nozzle rate and let a Flex Schedule throttle the watering according to ET.

You might learn the most by setting a Flex Daily schedule on this zone and watching the calendar change as you tune settings. If the calendar is too irregular for you, you could set a Flex Monthly, which will water in regular intervals, however this will not respond to sub-monthly heat trends (something we are planning on addressing). I would want that functionality for fruit trees.

Please let me know what you try and what the results are. I’m sorry it is so un-obvious how to do this right with our system in its current form.

how do we measure the area per emitter? I have zones with 4gph micro emitters that deliver a narrow stream (1/4"? diameter) and zones with 533 Irritrol Adjustable Flood Bubblers (delivering from 1.36 gpm to 5gmp) for which the spread area depends on how wide it’s open.

@beranes This illustrates the difficulty in accurately converting a volume rate to a linear application rate. In theory, if you measure the wet area under each emitter (and it was the same every time) you could use area to calculate the apparent linear rate (here, precip rate) with this equation:

Of course, that is a hard thing to do with an emitter with variable area, as you point out. With a system built around linear rates like ours, some guess-and-check tuning is inevitable. Your and others’ contribution to this discussion really has me thinking about how to offer a drip-specific mode where the schedule is determined by volume delivered, since the benchmarks and heuristics for drip irrigation are in volumes.

We would still do the math to tie the requested volume to (crop + shade-adjusted) ET, whether a customer would want it driven by ET (like turf zones) or simply wants an ET benchmark to compare to.

I agree with the formula, but shouldn’t the dimension of 96.25 be (in * min * ft2) / (gal * hr) ?

231 (in3 / gal) * 60 (min / hr) / 144 (in2 / ft2) = 96.25

@Stewart Thanks for pointing that out. (in * min * ft2) / (gal * hr) is the correct units for the constant in the denominator.

ECOBEARD, Can you post your full schedule? It looks you only posted December through June. I’m in Albuquerque and would like to set up something similar. I will have trees, shrubs, vines and flowers, but no grass.

It’s been a very wet monsoon at my house so I used way less than what was originally scheduled.

I got 4.14” of rain in July and 4.81” of rain in August.

The cyan is the trees/shrub mixed zone.
The green is the lawn.
The red is the flower pots.

The cyan on August 23rd is pots quick run manual to identify and fix a leak.

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What is the yellow (orange)?

They are the green fixed lawn on with rain skip. The cyan drip and red flower pots are flex daily

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These pics are when using Flex Daily or Fixed Schedule?

It’s a mix.


The lawn schedule in green and corresponding rain skip appears yellow.

Flex Daily:

The flex schedules are the shrub/tree zones in cyan and the flow pots in red. There are no rain skips for flex daily.

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Seems odd that the shrub/tree Flex Daily ran 2x in July and 4x in August, considering there were no rain skips.

EDIT: Oh wait, there’s another week in July not shown.

The shrub/tree zones went twice in July and 3 times in August

The cyan on August 23rd is pots quick run manual to identify and fix a leak. It’s not the drip.

I hope I’ve been helpful explaining my schedule. I know you get monsoon rainfall too. I get my weather observations from a neighbor less than 1/8 mile away and it seems very accurate as far as I can tell

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