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.