Flexible Daily with drip

I am using Flexible Daily with drip irrigation in several parts of my yard. Some lines use netafim and others normal drip with 4 gpm emitter heads with the number of heads on each plant varying depending on the type and needs of the plant.

I think the Flexible Daily is watering too much. What is the best way to adjust this? Dial down the percent of the scheduled amount or create a new emitter with a different rate? I see the emitters are measured in inches/hour and the heads are gallons/hour. So how do you best do this with drip without the calculations that I have seen on this board in a recent search?


Try this @bigbiggreendog to see if it helps?

Drip Emitter Calculator for Precipitation Rate & Area


Thank you.

I still have a few questions If I have a single drip that is 4 gallons/minute on a single plant, why do I need to count the number of plants on a particular irrigation line? I want to know what the corresponding rate is in inches/hour to create a custom irrigation head setting if needed. So what do you calculate for square footage for a single plant?

@bigbiggreendog, I also wrote a Drip Calculator that uses a slightly different set of inputs. Ultimately we need to somehow factor in the area that will be/needs to be wetted in order to convert from GPH to inches/hour. I used the average canopy area for the plants as an input, whereas @azdavidr used input from the Flex schedule.

The only reason to count the number of plants is to calculate the area, which is an output of the calculator. The calculator does give you the inches per hour and area, you just have to follow the instructions.

You don’t have to calculate area at all. The calculator gives you a number to use. Even then, it only factors into the estimates of how many gallons you used. It’s completely inconsequential for scheduling.

You state the reason to count the plants is to calculate the area. That would make sense to calculate the total area of the zone receiving irrigation. However, aren’t we trying to calculate the flow with drip irrigation for a single emitter [to one plant] and not the entire area? That is the part the doesn’t make sense for me. The choice for irrigation on selection of irrigation heads in Rachio is for a single emitter head. Correct?

Yes and no. I have to repeat, in my calculator the area has NOTHING to do with calculating the PR, which is what controls how much water you are putting down. All you need to know is how many gallons you want to put down per plant, the GPH per plant, and the inches-per-hour that Flex recommends, and you get the PR calculated for you. You can completely ignore the number of plants in the zone and the calculated area and you will still put down the same amount of water. IF you want Rachio to accurately estimate how much water you are using and report it to you, THEN add up how many plants you have.

You can prove it to yourself in the calculator. Change the number of plants from 1 to 100, and the recommended PR doesn’t change.

Not to muddy the waters, but here’s one other perspective. Taking a practical example, let’s just say we have this one mango tree in its own zone, and it has a single drip emitter:

(It’s not really on its own zone - I’m just pretending for sake of argument.)

Given the size of the wetting area below the tree (Arizona soil makes this possible), I can probably get by with that one dripper and still soak the root zone until the tree gets quite a bit bigger. But the number of gallons that that tree needs is going to go up as a function of its canopy diameter (its canopy area if you like). This is why my spreadsheet includes plant canopy diameter when calculating inches per hour from GPH. Since Rachio’s area inputs have nothing to do with watering time (just water consumption), we need to artificially feed Rachio a nozzle precipitation rate that corresponds with the number of gallons this tree needs.

I think there are improvements to be had in the Rachio software so it isn’t necessary to back-calculate precipitation rate, but for now I don’t see any other way to run flex yet still give this tree the number of gallons it needs for its size.

There’s something I’m understand about your calculator @ldslaron. What’s the equation that you use for your PR ? The spreadsheet is locked and the equations aren’t listed, so I’m not sure what you’re assuming.

Are you using it with Flex Daily ? If so, how do you guarantee the runtime ? The method I used was to put in your root depth, available water, etc. Once all that is done, Flex calculates how many inches it will put down each cycle. I then use that inches-per-hour for my PR calculation.

PR (in/hr) = Total GPH per plant * Watering Depth (in) / Watering Value (gal)

In my example, Flex wants to put down 1.19 inches. So, if I have 1GPH per plant, and Flex says it needs to put down 1.19 inches, and I want to put down 1.5 gallons, my PR is

PR (in/hr) = 1 GPH * 1.19 in / 1.5 gal = 0.79 in/hr.

The runtime will be:

runtime (hr) = Watering Depth (in) / PR (in/hr)
runtime (hr) = 1.19 in / (0.79 in/hr) = 1.5 hr

The #gallons work out, since 1 GPH * 1.5 hr = 1.5 gallons, which is what my goal was to deliver.

With your calculator not using the Watering Depth number (or Inches of Water applied), how do you tie it into the Flex runtime ? For a 1 ft diameter shrub, Water-Use-It-Wisely recommends 1.5 gallons. Your calculator correctly pulls out the 1.5 gallon number, but your calculated PR=2.04 in/hr for this example. If I used that in my Flex schedule, my runtime would be

runtime (hr) = 1.19 in / (2.04 in/hr) = 0.58 hr

The #gallons put down would then be 1 GPH * 0.58hr = 0.58 gallons, which was not the recommended amount.

Maybe you’re using a fixed schedule and setting your runtime manually instead of Flex where it does the calculation ?

@azdavidr, you’re right, and I’ve updated my spreadsheet - thanks. I wasn’t calculating quite the right thing. If we cover a 1’ diameter (6" radius) circular area with 1 gallon of water, Google tells us we’ve put down 2.04 inches of water.

However, I realized this isn’t what Rachio wants. It wants to know how many inches of water it takes to fill the gaps between the soil at depth. This depends on allowed depletion (AD), soil type/available water (AW), and root depth (D). We can figure this out ourselves: Inches required to fill up = ADAWD.

So now I think our spreadsheets should end up with the same answer, although I prefer starting from user inputs so I don’t have to “ask” Rachio how much water it wants to put down. I think you should be able to view the formulas now too.