A Beginners Guide on Understanding and Using ALL THOSE ***** NUMBERS!

I started this thread to tell basically everything I’ve found out thus far, in my short experience with Rachio, in the hopes of simplifying and helping other newbies. I was going to do it all in a single post, but realized that 1) This old retired engineer is way too wordy for that, and 2) People would fall asleep before learning anything. So I’m going to separate it into topics, which I will add to this thread.

Oh, and before I start, you Pros please feel free to call me out on any and all errors or misconceptions I have; no need to confuse people more than necessary, and I can take correction. I may cry a little, but I can take it.


What Schedule Should I use?

Naturally, when setting up your new system, you need to do as asked, and fill in all Zone information (except maybe the Advanced page, as you may not be sure about it). Best to save the Advanced until you know a bit more (although that my not take too long).

Next, you’ll want to make 1 or more schedules. A manual schedule, except in specific circumstances, will not help much, or at least will not take advantage of your new Rachio Smart controller, so it’s out, as the main schedule. And IMHO, Flex Monthly is out too, at least for the majority of your zones, because it will water ALL zones in the schedule on the same day. No one seems to mention that, but that alone is enough to turn me off; it just takes too much time to always water all your zones on the same day. While if you make a Flex Monthly schedule, you’ll find that out, I doubt most people know that up front.

So, Flex Daily it is. And very quickly, after entering your zones and answering the schedule questions, there you have it you’re (maybe) done. But I had a LOT of questions.

How Much Water per Week Will Be Applied?

I knew this with my old system, but had no idea with this. And why are the times so long? So confusing? It’s watering, but so much more or less than my old system. I added up daily times, and tried to calculate water flow, and ended up with different answers ever time I did it.

It turns out that finding out how much water your Rachio controller will provide each zone per day or per week is a snap: Click on any zone, then click on the Moisture %. It shows the Field Capacity graph; below it is a table (on a phone app, click More Detail to see the table. See the numbers in the Crop Evapotranspiration row? That is how much water Rachio wants your lawn to have each day. Either from rain or from irrigation. Right now, mine vary between 0.18” and 0.21” of water each day of this week. Adding them up for the current week, it gives 1.36” of water, in my case. That’s it, that’s how much water Rachio will give my lawn (assuming no rain). This week, at least on average. As temperature, humidity, etc. vary through the year, those values will change, watering less during cooler times, more during warmer times.

Where does that number come from? How is it changed? How is it calculated? Well, of all the variables within Rachio that you can change (and as you know, there are a bunch, and with all the explanations of “do this for more/less water/minutes/frequency/etc.”, there are only two things that change the water per week: Exposure (amount of sun), and Crop Coefficient (a default for which is set when you select your grass or crop type), each settable per zone. The final part of the puzzle is the (unseen) ET or evapotranspiration, which Rachio calculates each day based on previous, current and future temperature, humidity, etc. in your area of the world. And you can’t change that. Mind you, NOTHING else in the program determines inches of water per week (except Nozzle Flow Rate, but changing that should only be done with facts, not guessing, and will be discussed later). Not soil type, or depth, or slope, or any of those other fancy numbers. Shadier areas can decrease the water by 10-30%, but let’s consider sunny areas: Rachio will take it’s calculated ET value for each day and multiply that by the Crop Coefficient (mine’s 0.85), and it’s done. If the ET is 0.24", multiply that by .85, giving about 0.20” per day. Or about 1.4” per week. If your Crop Coefficient is only 0.65, it won’t need as much water, so Rachio would put down 0.24 x 0.65 = about .16” per day or closer to 1.12” per week.

Why do we care about this? Well, first, you can easily compare it to any previous system you used, if you know the inches of water applied. Second, you don’t need to change anything else to change your inches of water applied per week, should you want to. While the estimated Crop Coefficient for your grass might be right on, it also might be too low or too high (Warm Season grass is input by Rachio as 0.65, but research indicated that my Centipede grass should be 0.85). You can easily adjust the total water per week just by changing it. If your current values add up to 1” water per week, and you think it should be 1.2”, just increase the Crop Coefficient by 20%. Done!

How do I know it needs to be higher or lower? Watch your grass. If, over weeks (not days) it dries out too much or gets crispy, it needs more water. If it (almost) constantly stays soggy, it needs less water. 1” isn’t a bad value to start with, but it’s low for most of the country in the summer. Start with Rachio’s suggestion, but if needed, make the change to Crop Coefficient to increase or decrease it.


What About Nozzle Inches?

I know some of you will immediately say that to modify how much water your zone gets, you change Nozzle Inches per Hour on the Advanced screen of each zone. Yes, that will do it too. But I really don’t like it. First, while Nozzle Inches per Hour is on the Advanced screen, I kind of hate that it is. It is probably the most important number in determining how much water your lawn actually gets, and how healthy it stays. When you select your Spray Head type, it chooses the Nozzle Inches and Efficiency for you. Probably a good starting point. But at least in my case, many of these are off by a factor of 2! They just don’t know how good (or poor) a job your irrigation contractor did when setting up your system.

There are basically two ways of confirming, or changing, the value of each zone, both probably more than 80% (90%?) of people with irrigation systems do: 1) Calculate the area of each zone and measure the gallons or cubic feet of water applied to it in X minutes, then do a bunch of calculations to determine the average inches per hour (I had a spreadsheet, but them I’m an, uh, engineer). 2) The low tech, more time consuming, but far more accurate way of putting catch cups around each zone to measure actual, real, applied water for a given time. I’ve got the cups, now to do the work (it’s just been too darn hot here). If you really care about your lawn/crops, you really need to measure the water applied for a given length of time, for any system to accurately apply the correct water quantity. That’s just #1.

And since it is so difficult, or time consuming, or exhausting, to get those values for each zone, that’s why I don’t like to modify them. You sweated it out to get the values: USE THEM! If you’ve never done either of these to determine actual Nozzle Inches per Hour, sure, feel free to modify it up or down to change things, but as soon as you can, measure them. Then you have a definite value to use you are sure of, and as posted originally, go back to using Crop Coefficient if you want to apply more or less water to your lawn.


Interesting read Richard! Will def. revisit when I finally take the plunge from Fixed to Flex. Thanks for taking the time to write this up. - from a (fairly) old retired programmer. :wink:

How Much Water is Being Applied at One Time, or ‘Why am I watering the street when I don’t own it?”

It was surprising to me, at first, to find out that the total water applied by irrigation per week does not vary with root depth and soil type, as explained previously. Well, where do those come in? The main answer is: The amount of water applied at one time, or rather on one day, in each zone.

First, why do we care? If we give the lawn the 1.4” or whatever water per week it requires, does it really matter how much water is applied at any one time? Yes, it does, for the health of your lawn, in particular its ability to withstand hot weather. If we apply that 1.4” by watering just a bit per day, in this example 0.2”, we keep moisture in the top layer of the lawn, but never really water deep enough for the roots to grow, thus protecting the lawn and making it healthier. Watering every day is just bad for your lawn. Basically, every time you water, you should water enough to soak into the lower roots of the lawn, or at least where you’d like them to grow to.

Watering too much at a time is bad as well: Water will no doubt be wasted, either by running off, or sitting in puddles which can actually kill the grass. So how much is right? Rachio uses the Field Capacity model for watering, explaining with their Bank and Gas Tank analogies. I’ll use a bucket. You want to fill the bucket to the top, which will water to the bottom of the bucket (roots). The water then evaporates daily from the bucket until it reaches about the halfway point (an Allowed Depletion of 50%). If you let the water level get too low, it will stress your lawn, not providing enough water to the roots. If it’s too high, you overflow the bucket.

In our case, the bucket isn’t really empty; it’s filled with your soil, and different soils can hold different amounts of water. That’s the soil’s Available Water, which generally varies from 0.05 to 0.21, in my case 0.17. How much water, in inches, will your soil hold? That’s easy. For 8” deep roots it’s:

Inches of water held = AW x Root Depth = 0.17 x 8 = 1.36” of water

While the soil holds that much water, we don’t want to apply it all at once, because 1) we’d probably over-water, as it couldn’t accept it all at once, and 2) we don’t want the water in the bucket to ever be “empty”, or your grass will be on the point of dying. Rachio suggests a AD of 50%, which means we’ll wait until half the water is gone. That amount of water is:

Inches of water held = AWC x Root Depth x MAD = 0.17 x 8 x .50 = 0.68” of water

That value of represents the amount of water that Rachio will apply every time it waters, unless it reduces it due to rainfall, and answers the question we started with. It’s trying to top up the bucket every time it waters, then waits until the bucket is half full before watering again.

Once again, there are surprisingly few variables that affect the water applied at one time: the Available Water (determined by your soil type), the Root Depth (determined by your grass or crop) and the Allowed Depletion (you get to choose that one, but it should probably stay not far from 50%). If you want to water less often, you can decrease the Allowed Depletion some; if you want to water more often, you can increase it some, but watch that you don’t overflow your bucket and waste water in the street.

Note that changing these variables will change the amount of water applied in one day, and also the total amount that Rachio thinks your soil will hold, but it will NOT change the total water, on average, that your lawn receives. That is done only by the Crop Coefficient, as explained in the first post above.

Also note that while the amount calculated here will be applied each day Rachio waters that zone, it may not be all applied at once. Letting Smart Soak do its job will let the system break the 0.68” up into 2 or more separate applications with soak times between, totaling 0.68”, but allowing your yard time to soak it up. This is often necessary for soils such as clay, which hold a lot of water but absorb it very slowly, and for sloped yards, which let the water run off if too heavy.


How Often Will Rachio Water My Lawn?

Everyone wants to know how often their system will water. Usually because they have experience in programming a less-automated system previously, and want to know how it compares. As mentioned earlier, Rachio’s Flex Daily uses the Field Capacity method with a specified Allowed Depletion. And as stated previously, it will always water the full amount calculated previously (unless rain occurs) each time, then wait until the Crop Evapotranspiration value indicates it’s time to water. On average, the system will water every:

Days Between Watering = Total Water Applied / Daily Crop Evapotranspiration Value

We calculated the Total Water Applied in the previous post; it was 0.68” for the example given. Your value, without calculating, will simply be the highest Irrigation value in the chart for each zone over several weeks. The amount watered can vary due to actual or anticipated rain, but the maximum amount will always be the same.

The Daily Crop Evapotranspiration value varies with each day. In the previous example, it was running about 0.20” per day. So in this case:

Days Between Watering = 0.68” / 0.20” = 3.4 days

The system will water about every 3.4 days, or just about twice a week. As mentioned in the first post above, the amount of water used per week varies with temperature, humidity, time of year, etc. In our case, it does this by changing the water used by your lawn per day, the Daily Crop Evapotranspiration. When the weather cools down, this value will be lower, and therefore the time between watering will change as well. When the daily water use lowers from 0.20 to 0.12, for example, days between watering would change to:

Days Between Watering = 0.68” / 0.12” = 5.67 days

In operation, Rachio always waters the same amount at one time, then waits a varying number of days until the soil nears the depletion value, then waters to fill the bucket up again.

Should you want to change this, you have to change the Total Water Applied at one time (since you can’t change the temperature). Assuming you’ve entered your values correctly, this means changing the Allowed Depletion (from 50%), or possibly Root Depth. In my case, the average value of Root Depth for Warm Season Grasses was 9.84”, but I have Centipede grass, which I found has shallow roots, only 6-8”, so changed it accordingly.

You probably shouldn’t change these values much; Rachio has a reason for wanting to soak your lawn well, then let the top part dry out (the Allowed Depletion); this brings oxygen to the roots and helps the lawn in many ways. But you can adjust it slightly if desired.

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@rraisley Richard, thanks for putting this together. I was looking for something like this from Rachio but was quite surprised to not find it. This is very helpful for getting my new Rachio controller working properly.

Coming from conventional controllers (Hunter, Rainbird) with fixed schedules and seasonal adjustments (solar and rain adjustment on the Hunter X-Core), it takes some getting used to the idea of trusting the system to optimize watering.

We bought a house with a highly irregular yard. I’m working to improve the Hunter PGP rotor locations, rotor sweep angles, individual rotor nozzle flow rates, and zone run times for a healthy lawn with reduced water use. We have a lot of forest shade at different times of the day and seasons, so we are prone to moss growing in the grass here in the Inland Northwest. That is especially true if we over-water. So optimizing the system for healthy turf, minimal moss, avoiding boggy spots, etc is a real challenge.

Thanks again for taking the time to put your documents together. You are doing Rachio’s job for them.

Question…is there a way to export the History data? The History information available in the mobile app is good, but it would be nice to see the run time of all the zones in a single Excel table.

  1. Not really, but thanks. They do a good job of explaining each variable, but I didn’t always understand what the results were. With Flex Daily, it all comes down to 1) How much water is applied at a time, and 2) On average, how much water will be applied per week.

  2. Ah, a fellow Excel-ent person! I looked, but don’t see it. I entered all my run times into an Excel spreadsheet too, then graphed how much water is applied for each day, and doing that helped me understand how it worked. But now that I know, I don’t feel the need to do that.

I can’t emphasize enough, though, that real Nozzle Inches per Hour is so very important. Many people misunderstand what this number even represents, and based on my yard at least, the values given are not at all representative. My son’s going to help me get catch cup readings this weekend, and then I’ll probably end up changing everything! :wink:

BTW, does anyone know how to have multiple quoted areas within a post? The normal [quote]Text[/quote] doesn’t seem to work. It wants to quote from the first to the last, along with everything in between.

If you want to quote a subset of a post just highlight the section you want to quote and then select the quote button when it appears. Then if you want to quote another area go back and highlight the second area.

Here’s the 2nd quote for example.

Thanks for the quick reply. I bought a couple of boxes of catch cups a couple years ago and haven’t used them yet. I need to draw a decent map of the yard and put the cups out – hopefully in the next couple weeks.

Real Nozzle Inches per Hour is tough because I’ve got some rotors going 360 degrees, some going 180, some doing 90 degrees. I have different size nozzles in each rotor depending on the sweep and water requirements of that part of the yard (the shaded areas need less water, the bright sun areas need more). I figure I’ll use the catch cups to collect a number of data points per zone to get an overall estimate of inches per hour over the entire zone, then divide by the number of nozzles (rotors) to get an average inches per hour per nozzle rate.

@rraisley – Repeating my reply, this time using “@”…

Thanks for the quick reply. I bought a couple of boxes of catch cups a couple years ago and haven’t used them yet. I need to draw a decent map of the yard and put the cups out – hopefully in the next couple weeks.

Real Nozzle Inches per Hour is tough because I’ve got some rotors going 360 degrees, some going 180, some doing 90 degrees. I have different size nozzles in each rotor depending on the sweep and water requirements of that part of the yard (the shaded areas need less water, the bright sun areas need more). I figure I’ll use the catch cups to collect a number of data points per zone to get an overall estimate of inches per hour over the entire zone, then divide by the number of nozzles (rotors) to get an average inches per hour per nozzle rate.


Then if you want to quote another area go back and highlight the second area.

Weird. Works, but weird. Turns out my method works too, using [quote] and [/quote] but only if those are on their own line. Same with the “>” you used. Different, but now I know. Thanks.

Can you have more than one Flex Dailey schedule? I have my cold weather grasses on Flex Dailey and the areas with more shrubs than grass on Monthly. I seems I would be better putting them on a Flex Dailey too.

I very much enjoyed the information you shared.

Right there is something that I think the terminology is all messed up on. Nozzle Inches per Hour does NOT mean how much water is produced by each nozzle (as it says). It means how much water is applied to your lawn (by the nozzles). For Rachio to ask how much water each nozzle puts out, it would then need to know the area each nozzle waters, and as you say, 360/180/90 degrees. I very much dislike that terminology. A recent long post complaining about the complexity mentioned that we should just put in the type of nozzle we have, and Rachio would use it. But again, that’s not the meaning. (And even if it were, most nozzles can be “throttled” to put out more or less water, to determine the distance the water travels.)

IMHO, Nozzle Inches per Hour should be called “Inches of Water Applied per Hour”. There are two ways of doing that: 1) Measure actual water used for a given period of time, measure the square feet covered, and calculate the average inches per hour - that’s what I’ve done so far. 2) Use catch cups for a given time to calculate average inches per hour and Efficiency. More time consuming, but MUCH more accurate.

If you’re interested, I’ve made a spreadsheet specifically for using 12 of the Orbit catch cups, which calculates average water inches per hour (to input into “Nozzle inches per hour” in Rachio) and Efficiency. Apparently I can’t upload an Excel file here, but if you PM me your email, I’ll send it to you.

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You can only have one Flex Daily schedule for any given Zone. So you can put the zones with the cold weather grasses can be on one Flex Daily zone, and your shrubs on another Flex Daily zone.

I see NOTHING difficult or complex about the Flex Daily zone once you know how it operates. I wouldn’t use anything else, because only Flex Daily takes into account the actual weather conditions you’re having.

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Thank You.
Your response is very much appreciated.

I couldn’t agree with you more!!! It make take a little time and effort to learn it, but its worth every minute that you put into it.

I was wrong; there IS a download to CSV available. It’s only for each zone, so go to your Zone, scroll down below July Usage to date, and you’ll see a Download arrow. Clicking it gives you that zone’s Date, Hours usage, Gallons Usage, and Savings data. IMHO, only the Hours Usage means anything, unless you’ve properly calibrated both your “Nozzle” inches per hour and your Square Feet area, or if you’re using a Flow meter. But I think Hours Usage is what you want anyhow. Repeat that for each zone, placing each in a separate Excel column, and you can get a month’s data for each zone.

From the Home screen (I’m talking about the web screens here, but that’s where you’d usually download to Excel), there’s also a Download button. It downloads the TOTAL times and water usage, but does not separate by zone, so would be less useful IMHO. But it’s there.

IMHO, Flex Monthly is no less difficult. ALL of the same Zone variables are in effect with Monthly. It still takes into account the Advanced variables of Available Water, Root Depth and Allowed Depletion to determine how much to water at once time, modified somewhat by the Crop Coefficient and average ET values for the month to usually water every X days, which can change the watering time as well. And it appears that it does not take into account daily rainfall, at least not in a very accurate way. And it gives you none of the valuable (to me) information about soil moisture or depletion. And it does not account for hotter or cooler than normal weather, as it uses average, historic values. I’m sure it does a fine job on average, but with all the variables meaning just as much, I like seeing what’s going on with my zones.

Way back in April of 2016, Rachio was really pushing all of it’s users to not use Flex (which is now Flex Daily), and to use As Needed (which is now Flex Monthly). There was a BIG backlash on the community, as the Flex users at the time saw it’s benefits and absolutely did NOT want to be forced into using what is now Flex Monthly. Rachio listened (one of the reasons I REALLY like Rachio), made some changes, and Flex Daily was born.

I don’t really understand why people want to use Flex Monthly for it’s “predictability”. I’m pretty sure it’s all based on historical data. Definitely not current data of what is happening this week. Just doesn’t make sense to me, as some years are droughts, and some years it rains every afternoon.

And you are right, the set up is exactly the same. But because it’s “predictable”, maybe the tweakings of the settings don’t make as much difference anyway, because your’e not really basing your watering on current conditions.

And Flex Monthly waters all zones in the schedule when it waters. So if I group all my grass zones together, it will get watered based on the needs of the most sensitive zone. So it would NOT take into account that my front yard is in full sun and dries out very quickly, that I have an area under trees that needs a little more water applied, and that my backyard is in the shade, doesn’t drain, and can easily become a swamp. It would make a mess of my yard.

OK, off my soapbox. Guess you can tell that I’m NOT a fan of Flex Monthly in the least. Set it up right, and Flex Daily works great. Gives my yard the water it needs WHEN it’s needed.

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