Las Vegas Summer Setup and Programming for Flex Daily

Hello all, got my rachio 3 a couple weeks ago and I have been trying to understand this smart timer thing vs. what the Nurseries tell me. Reason I am writing this and asking for help is I am getting conflicting information. Star Nursery is telling me I should be watering every other day right now. rachio is only running once per week right now. We are talking close to 110 each day this week and it only wants to water once. The system watered for 90 min on 07/02. On 07/08 the system was showing Soil Moisture at about 25% so did a manual run of 120 min. The next scheduled run is 07/12 then on 07/19.

Is this correct? that seams quite a long time between waterings at at 110 temps?

Here is what I have
Like most, I have a one drip zone system for the front yard. Landscapers were cheap :slight_smile:
I have 2 trees;
Desert Museum Tree (20’ canopy) - total GPH is 13
Flowering Plum (4’ canopy) - total GPH is 11 (this is the most important plant)
Sage and Rosemary (2’ canopy) - total GPH is 2
Compact Xylosma (2’ canopy) - total GPH is 4

Zone set up
Zone Type - Shrubs
Spray Head - Emitter
Soil Type - Clay
Exposure - Lots of Sun
Slope - Moderate

Advanced Settings
Area - 500 sq feet
Available Water - .15 in/in (what is this)
Root Depth - 24in
Allowed Depletion - 50% (what is this)
Efficiency - 100% (what is this)
Crop Coefficient - 50% (what is this)
Nozzle Inches Per Hour - 0.9 in. (I think I understand, but not 100%)

When it waters, it starts at 6am and runs for 120 min.

I have to say, the shrubs look ok. It is my flowering plum that has me stressing. It’s leaves are looking wilted and this is my 2nd attempt at growing one. I planted this tree Sep 2018, almost a year to talk hold before the summer hits.

So is once a week correct for Las Vegas summer?

How do I tell the system how much water the pants are getting? I feel like that is the once piece of info the system does not know. How does it know the size of my drip emitters?

Any help/understanding would be greatly appreciated.

Thank you,


I have the exact same question. I realise this was some time ago - but did someone help you with this?

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Hi FizzaFarian, nope no one ever got back to me nor made any comments on my post. Heading into the summer again and no clue how to set this thing up. There is no way this is right to wait a week or two in between watering in Las Vegas.

Belatedly… You have all the information you need to get closer to the answer for watering.

Use the equation from to calculate in/hr, where you’ll convert your most important tree’s gallons per hour to gallons per minute and use your most important tree’s drip line area for the area. If the canopy dimension you have is the diameter, then half that and use pi*r^2 to get the drip line area. You’ll set the drip zone to water your most important plant.

For example:

11 gph / 60 min/hr = 0.183 gpm
4 ft/2 = 2ft = r
3.14*2^2=12.56 square feet

(96.25 * Q) / A = PR (nozzle or precipitation rate)
(96.25 * 0.183)/12.56 = 1.4 in/hr

I suggest not using the default 24” for root depth as not many trees root that deeply and most trees seem to get the bulk of their water near the surface. I have found 8-12” root depth sufficient for trees.

Mess with the above advanced settings first then crop coefficient (see below). There is a discussion thread on soil Available Water but don’t have the link handy right now.

Allowed Depletion is fine at 50%.

For drip, 100% efficiency is fine but in reality is slightly less.

Crop coefficient is hard to find but really important. It’s how much water you plant uses. A plum in the desert will likely have a high coefficient closer to 90% to 100% or higher for the summer. Check your regional ag university extension to see if they have crop coefficients or ETc for stone fruits.

@FizzaFarian I just attempted an answer.

@Kubisuro too me some time to get back and play with his. I really do appreciate the work you put into writing that up. I do wish this was more user friendly, this is very complicated to understand and watering your yard should not be. I reworked the settings based upon what you said and the issue I am having is the duration between waterings. It is Las Vegas, NV, we are running 107 to 110 every day right now. Soon it will be well into the 100s even at 1am. This is where I can not get it past my head, the system is saying that it watered on the 06/23 and will not water again until 06/29. That is 6 days in over 100 temps, no one in this town will tell you to wait 6 days between watering during the summer, and that is the people at the nurseries. Some say daily some say every other day. But when I say once a week they say I am NUTS. If this thing was going 2 or 3 days between watering, fine. But 6 days. Someone will have to explain to me that is correct because I just do not buy it.

Again, I do appreciate your help

Hmm; sorry to hear that. You may need to increase the default evapotranspiration for Las Vegas – maybe add 10-20%. You can investigate what’s going on by looking at the soil moisture chart. There’s lots of hidden rows so be sure to click the tiny grey sideways triangles. You should be seeing evapotranspiration values around or above 0.30". The root depths in advanced zone settings can always be reduced to help reduce watering time and increase frequency.

But if you’re tired of messing around with Flex, it’s totally fine to revert back to a watering schedule you’re used to. There’s still lots of functionality Rachio provides for fixed schedules, so you won’t be wasting the device at all.

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