Flex Daily Settings - Redusing Water Frequency and Duration

I purchased the Rachio Controller for ease of use and to reduce water usage. My existing system was overwatering. I set up the flex daily schedule for a pretty basic lawn – almost all cool season grass in southeast Michigan on flat ground, some shade, typical sandy loam soil. With this information, the default settings were not much different than how it was being watered before. It keeps the grass very green, but it’s almost always saturated. It’s hard to even enjoy the lawn because it’s always wet. I don’t want that.

I have tried lowering the root depth to 5", dropped the crop coefficient to 65%, and the boosted the efficiency to 95%. That successfully lowered the watering time, but it still seems to want to water more frequently. The moisture level went from 110% to 45% overnight on not-so-hot day.

Also, I have most rotor heads. Many of them only make a 1/4 turn. Wouldn’t that result in double the in/hr of the same head making a 1/2 turn?

Many of these settings are foreign to me, and I’m adjusting them to get the watering duration and frequency that looks right based on my observations, but they don’t seem to align with the recommendations. I would just set the duration manually, but then I would lose a lot of the automation benefits. Any suggestions? I don’t need golf course grass. I’d rather save on water costs.

Perhaps the watering time is similar, but the frequency may be different? It’s not always obvious with Flex Daily how often the lawn will be watered. What were your time & frequency previous, what is your time now (and post a graph or table of a typical zone, if possible).

I agree, you don’t want that. Used properly, Flex Daily may saturate the lawn the day it waters, but it should then allow time for it to dry out. I just watered some zones yesterday, and the guy who mows my grass had no problem today, using a riding lawn mower. It’s not soggy at all.

Okay, by default, cool season grass has 5.91" deep roots (they use a micrometer :crazy_face:), and 78% Crop Coefficient, and Sandy Loam Soil has an Available Water of 0.12"/". With 50% Allowed Depletion, Rachio’s Flex Daily will want to apply 0.12" x 5.91" x 0.50 = 0.35" of water. I’m guessing it will want to apply that every 2-3 days, depending on your temperatures. Dropping the root depth to 5" will change the water applied to 0.31". Even with a crop coefficient of 78%, I would expect that to last 2 days, but with a reduced ratio of 65% it’s gone in less than a day (110% to 45%); at that rate, it would have a hard time going to every other day.

I would leave the root depth to 5.91" (actually, I’d change it to a reasonably rounded 6"). Your soil is pretty well fixed, and I wouldn’t go below 50% Allowed Depletion, keeping the 0.31" of water applied at once.

The Crop Coefficient has no effect on the amount of water applied at once, only how quickly it will dry out. If your hard has been running wet, dropping it from 78% to 65% might be okay; you’ll just have to watch for it drying out.

Rachio gives 1" per hour as the Nozzle Application Rate. This is the average water applied over the zone by your heads, regardless of type and 1/4, 1/2 or 360 degree heads. On my lawn, the application rate is substantially less than 1", actually running between 0.4 and 0.8"/hour. But lowering this value would water more, not less, so I wouldn’t change that for now. Setting efficiency to 95% vs the recommended 70% will reduce water and time by 15%, although that usually isn’t the purpose. It’s purpose is to allow more water to be applied if the water applied to a zone is really uneven, to be sure those areas receiving less, get more water. My efficiencies are really low, but regardless, increasing efficiency does reduce water applied, as does increasing nozzle flow.

Agreed. The settings and terminology are foreign to me as well, but we learn them, if interested. With Flex Daily, only two things matter (and those are calculated based on the other factors): Water applied at once (if too little, roots will never get water, if too much, puddling and flow off the zone will occur), and how much water the zone uses each day (determine by temperature and Crop Coefficient, too little will dry out over time, too much will get soggy over time). I think I and others can help you get the right balance.

Oh, and @prattleon, you stole what I really should have called myself here on the forum! :wink:

Thanks for your response!

We’ve had a lot of rain, and have a lot in the forecast, so I haven’t been able to really see how it’s behaving with my new settings. There is a moisture chart/table for a typical zone below.

Prior to installing the Rachio the lawn was being watered 3 times a week for 20 minutes on each zone. I didn’t set that up. It’s a small association and I recently took over the lawn care. As I mentioned, I always felt like it was being over-watered. I could rarely sit in the grass for more then a 20 seconds without getting wet. The lawn looked great, but it seemed unnecessary.

With the default settings on flex daily, it was watering nearly every other day for 25 minutes. I made the following adjustments to reduce the duration to 11 minutes, but I feel like I had to fake it into that. What about my grass/soil/heads/etc are really resulting in the need for less water than the default setup?

Zone Setting Adjustments:
Soil Type: Sandy Loam --> Loamy Sand
Exposure: Lots of sun —> Some Shade (I’m probably on the border, but many areas I feel are firmly in the lots of sun category)
Efficiency: 70% --> 95%
Crop Coefficient: 78% --> 65%
Root Depth: 5.91" --> 5"

I feel like the controller algorithm is attempting to converge on a correct amount of watering based on an impossible complex set of criteria. I don’t think it’s possible to accurately follow the moisture level in the soil without physical measurements, or resetting it after a very heavy rain when it is known to be saturated. I’m just trying to fake my settings to get it watering about where I want it to based on my observations. It could be my lack of understanding, but the added level of complexity and finite adjustment (which very much interests me) don’t seem beneficial.

Okay, just looking at the chart above, I can see that it is a zone where you are considering Loamy Sand with Available water of 0.07"/" and 5" root depth. That calculates out to 0.07 x 5 x 50% = 0.175" of water per time, which checks out with the 9/5 irrigation amount of 0.18". And while I think the values are low, the Crop Evapotranspiration values for this week go from 0.04 to 0.11, totaling 0.51" for the week, or averaging 0.073" per day. So, using this setting, Rachio will water the zone 0.51 / 0.18 = 2.83 times per week or every 2.47 days. I like calculating it this way because 1) It’s right, and accurate, and 2) Doesn’t get fouled up by having rain scheduled.

Since minutes watering time = Inches of Water / Nozzle Inches per Hour x 60 x Scheduling Factor

and Scheduling Factor = 1 / (.4 + .6 x Efficiency) , for 90% Efficiency, SF = 1.0638

Turning the equation around: Nozzle Inches per Hour
= Inches of Water / Minutes x 60 x SF = 1.045 "/hr, if Minutes = 11 as stated above.

That is close to the 1" per hour that Rachio recommends, so that all seems to check out.

BUT - This means that Rachio will be applying 11 minutes of water 2.83 times per week on average, or a total per week of 31 minutes. Which is definitely less than you say the original controller was applying (20 minutes 3x per week = 60 minutes).

You say that with the original settings, Rachio was watering 25 minutes nearly every other day. Of course that was before you changed settings. And, to be honest, the weather was probably hotter then. But even using 25 minutes, if that was 2.83 times per week, that’s 71 minutes per week, not that much different than the original controller.

While your crop coefficient seems low, and therefore your daily Crop Evapotranspiration seems low, that is the best way to limit the amount of water applied over time, and you say the ground stays moist, so probably not a bad way to continue. Root Depth & Efficiency are fine. Loamy Sand has a AW of 0.07 and Sandy Loam 0.12, so that’s a huge difference there, which would result in 0.30" of water being applied at one time. But this would also result in the frequency of water being only about 40% of what it is now, and that’s kind of what you want. Assuming you’re kind of guessing as to the soil, which most of us do, rather than it being a specific soil for each zone, you might try an average 0.10" for Available water. That might be a good compromise to put more water down at once, extending the time between watering. Ground will ALWAYS be squishy when it’s watered (topped up), but should have a chance for the upper portion of the soil to dry out before watering again.

Again, sorry for the babbling, and I’m not sure how much detail you want to get in to. I think setting your AV to 0.10 and letting it run for a while with the rest of the settings isn’t a bad way to continue for now.

Thanks for your help! Your calculations helped me understand what the controller is doing with the settings I enter. I’m going to keep an eye on it for a while when the weather dries out a bit. It’s probably going to take a bit more tweaking.

We had a period with a lot of rain, and temperatures dropped off pretty sharply. The controller did a reasonable job of adjusting watering but I have skipped about 5 waterings recently because they didn’t seem necessary. The lawn has not been watered in nearly 2 weeks and I see no indication that it is needed, despite what my Rachio controller says. I’m not sure what to make of that. I feel like I already aggressively tweaked the settings.

Also, on several occasions I skipped a run the night before and it started running anyhow. I’m not sure why that happens sometimes. Anyone else have that issue?