Question about Run Time

I am trying Flex Daily for my Grass Zones and had two questions.

I recently switched my nozzles from Fixed Spray to Rotary Nozzles (Hunter MP Rotators). I chose to water everyday except Sunday. Flex Daily is suggesting a single 49 Minute Water Cycle everyday. If I choose to go back to Fixed nozzles it does Two 11 minute cycles with a smart cycle soak in between. Our Water Authority here recommends watering grass 3 Cycles of 4 minutes each and as many days as needed. This seems way off from their recommendation.

My first question, does this amount and frequency seem normal for my area?

Is the system functioning normal by not using a Smart Cycle with Rotary nozzles?

Here is some of my data
I live in Las Vegas and the Total Weekly FRET right now is 2.5 for my area.

Cool Season Grass
Rotary Nozzle
Lots of Sun

Advanced (All Default)
381 sq ft
0.17 Available Water
5.91 Root Depth
50% Allowed Depletion
80% Efficiency
78% Crop Coefficient
0.7 Nozzle Inches Per Hour


Curious how you calculated your nozzle inch per hour? Did you use the precipitation rate formula (GPM x 96.25 / sq ft of area)? Doing a reverse calc with your .7 nozzle rate it appears you would have 3 GPM, which seems low because that would most likely be only one sprinkler head. How many sprinkler heads do you have for the area? The GPM to use in that equation is the total of all heads. You can also can account for degrees, like if you have a 360 degree rotary head at 3 GPM but only have the spread going 180 degrees then the GPM would be 1.5 (which is 180 / 360 x 3 GPM). The GPM total may be your issue since increasing the GPMs will not only increase the nozzle inch per hour rate but also reduce the time duration recommended to water.

OR, could be since you’re in the Vegas area probably with water restrictions your water authority is recommending the bare minimum. Using Rachio with Flex Daily and having all the advanced settings fine tuned to your lawn will water what is recommended for the healthiest lawn, i.e. ideal conditions.

Hope this helps!

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The Nozzle Inches per Hour was the default setting. If I set it to Fixed Spray Head its 1.5 in and Rotary Nozzles Sets it to 0.7. I have about 6 Spray heads in each area. I looked up my MP rotators and they list a 0.4 inch per hour rate. So if I change to 0.4 runtime is going to take 1hr 30 min per zone. Just seems to be a long time for sprinklers to run.

Wow those heads are low flow. And unfortunately what you have set is pretty accurate. So ideally for cool season grass with those heads 90 mins is about right every 3 days. That would be about 1400 gallons used in a month. Depends on root depth too, if you can measure that and reduce root depth for Rachio that’ll reduce watering time but also increase frequency.

I don’t know what to recommend based on your water authority rules. I don’t think your grass will survive with what they say, at least not with those heads. Do they enforce you to stop watering after a certain amount of gallons are used per month?

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Using your current weekly FRET of 2.5 (which seems right) and your Crop Coefficient of 0.78, you lawn needs 2.5 x 0.78 = 1.95" of water per week.

You listed an Area of 381 sq ft and mention it is the Default, but I don’t think Rachio sets a default for Area. In Rachio, it is only used for water savings calculations, although it is often and best used to calculate actual flow rates along with GPM of water use.

Ignoring area for the moment, if your Rotary Nozzles are supplying 0.7" per hour, then your system will have to currently run for 1.95 / 0.7 = 2.78 hours = 167 minutes per week (190 minutes considering Efficiency). The 49 minutes run time is correct to apply its recommended 0.50" of water at one time, but I would expect it to run 190/49 = 3.9 times per week or every 1.8 days.

Watering 12 minutes per day gives less than half the water your lawn currently needs, although that may be fine in milder weather.

Flex Daily, Flex Monthly and Fixed use different parameters to calculate watering time, and water at different intervals. To compare them, calculate total time over a period like a week. Also realize that Flex Monthly uses AVERAGE temperature for July, which may be different than your actual temperature, which Flex Daily uses.

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MP Rotators are my personal favorite, and I have a yard full of them. Your run times seem pretty accurate. With my settings here in Arizona, my sprinklers run1h10m minutes per zones, and run every couple days (it is 105+ here right now). Since the MP’s aren’t the only rotary nozzle on the market, Rachio’s default PR is a bit of an average amount those out there. In real world, I’ve seen the MP’s put down closer to .5-.6", so realistically, you might still be a bit short on the duration.

They are very low flow in comparison to many fixed spray heads. I hate when utilities/people make blanket statements on duration/frequency for your sprinkler system. Every yard is different, and no two will be the same. Your utilities recommendation might be accurate for someone with some supper high flow VAN spray nozzles (I’d argue that is still low, but I assume they are trying to force people to eliminate runoff, and thus save water), but if you water anywhere near that with the MP’s your grass will be dead in a week.


These are rotary heads, not Rotors. Arc doesn’t play into the equation on these kind. They are just super efficient spray nozzles with a rotating head on top.

By the way, I love the rotary nozzles on the MP Rotators as well. It takes some getting used to after having only used the various higher volume heads previously. Even my wife thinks the spray is pretty compared to other sprinklers. These are really resistant to wind which we get most mornings and evenings. Even with the wind, we hardly have any overspray, never have runoff (of course, we also have loamy sand) and get really pretty good overlapping coverage. I do not like the blanket statements from utilities or other people either.

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Not sure what you are talking about? :nerd_face:

I’m not familiar with Hunter’s rotary heads. The Rainbird rotary heads I use have adjustable arc’s and higher flow rate.

As do the Hunters, but they have one of the lowest flows in the industry, which is how they claim the water savings since it is almost impossible to have runoff with these.

I meant to say that I have ran people that have used the MP Rotators that either LOVE them or HATE them . . . with nobody in between that I can think of. I do not actually remember why they do not like them, but maybe it was that the water needs to be pretty clean. In other words, I would guess culinary water works better than others. I have PI and at the end of a line. I had one filter for the system and then other smaller filters for drip. I have ended up taking out all the filters and put the finest filter for the entire system. Then I clean it probably at least once a month. I believe being the end of the line is what makes the difference as I was talking to another neighbor and they checked their filter after three years and it was clean. They also may be more susceptible to number of heads, watering distance, and pressure. In other words, one zone seemed to frequently get a head or two that would stop rotating. After I split that into two zones last year, I have not had any issues. I have two other zones that seem to have an issue, so I am splitting the two into three zones, which I think will solve that.

The precip rate stays nearly constant as you adjust the pattern, but the gpm overall (which is what @questioneverything mentions) definitely changes as a result, with a 180 deg pattern using roughly half the gpm of the 360 deg pattern.

GPM yes, precipitation rate, no…Doesn’t matter if it is 45 degree or 360 degree, the precipitation rate of the MP’s will be the same (assuming consistent head overlap).

Right… Which is why @questioneverything was correct.

Doesn’t Hunter list the nozzle inch-per-hour at around .4-.5 inches/hour for most of those at 40psi?

Consider yourself lucky. My controller on daily flex tells me to water 12 hrs a day. (North Texas, Wsrm season gas, Rotary Nozels).needles to say that can’t happen. Part of my reason for switching was conservstion, this has me watering about 5 times what i was watering.

If you post your settings (screenshot), maybe the community can help you.