Zone Settings for Subsurface Drip Tubing


This will be my third season using Rachio. Up until now, I have been unable to figure out flex scheduling. My zones so far have all been small and drip; I’ve just used fixed watering times for the most part. I’ve been unable how to accurately figure out how to set up my zones so the water correctly with Flex.

I just installed a new yard and would like to set up Flex schedules.

My new yard (small I know) is 156 sq ft.

It is watered with 182’ (175 emitters) of Rainbird XFS-06-12-100 sub-surface drip irrigation ( ) pressurized at 20 psi.The dripline is rated at .61 gph and a working pressure range of 8.5 to 60 psi. Is that .61 gph per emitter and should each produce that, regardless of what the working pressure is, as long as it is withing the specified range, or will it emit less at 8.5 psi than at 60 psi (or my working pressure, 20 psi)?

What spray head type should I use? None of the choices are drip line. I’ve selected emitter.

What values should I use for Available water? What units are these?

What about root depth? Is this effected by the fact that the drip line is below the roots? I think I am around 4" deep below my cool season grass sod.

What value should I use for Nozzle inches per hour?

Lastly, how do I determine what to use for “Allowed Depletion”, “Efficiency”, and “Crop Coefficient”?

This is new sod and I would like to apply the recommended 1" per week and don’t know how to set up the zone so this is done close to correctly, with either flex schedules or fixed schedules.

Thanks in advance!


A little deeper searching found this:

and this:

(online calculator link does not work)

If my math is correct:
.61 GPH = 0.01017 GPM (from

PR = (96.25(A * B)) / C

1.098082692307692 = (96.25(175 * 0.01017)) / 156

Basically, my PR = 1.1

What is PR? Is this Nozzle Inches Per Hour?

I think I have my head around Allowed Depletion and Efficiency. My SDI should be very efficient.

I’m using 50% Allowed Depletion and 90% Efficiency.

What do I use for “Crop Coefficient”? I selected “Cool Season Grass” for my vegetation type (70% Perennial Ryegrass and 30% Fine Fescue). It looks like the software defaulted to 80. This page

says 70. This thread Crop Coefficients and @franz indicates it is different every month and to use an average. The average of @franz’s values is 78.3 year round and 88.6 April - Sept. Should i Use 70, 78, 80, or 89?

Outstanding, I would like to figure out what value to use for “Available Water” (I understand what this is, how do I calculate it and what units is it?), “Root Depth” (How is this affected by subsurface drip; effectively at the root?), and “Nozzle Inches Per Hour” (Is this the PR value above?).

Thanks again.


Any thoughts on this? Am I headed down the right path?



What made you decide on using subsurface drip irrigation? What was the cost of installation/tubing?


I wanted it to be invisible. It’s a small patch of grass, 26’ x 6’. Was easy to install myself.

As a bonus, no one can see when I am watering.

2 x 100’ rolls and the fittings and a filter and air relief valve and operation indicator plus the necessary pvc was about 150, I would guess. About $1/sq.ft.

I think it will work well if it doesn’t clog.

I ended up figuring how close to put the rows, I think it is 10” or 10.5” or so. This puts the emitters staggered every othe row about 12” apart, which is the spacing on the tube between emitters. Hopefully it will be very even.


Any followup on the settings you settled on?
I’m using the same dripline on a similar size patch of lawn in my back yard here in San Jose. I ended up with 12" spacing at a depth of 4" from surface. Since I had a dead patch of lawn I figured it would be fun to experiment with subsurface for this patch when I re-seeded.

I started with the default settings for the zone (cool season grass), and have been trying to tweak them.
I’m currently running 1h 48min about every 5 days or so.

However, the lawn has taken on a polka-dot appearance. I’m assuming the water just isn’t spreading out enough in the time it waters. I’m not clear if I need to water longer, or more frequently with less duration.


Mine waters about 29mins every 5-10 days my lawn is nice, green, and vigorous. My neighbors is brown. It seems to be working well. I used the 12” between emitters and have 10+” between rows. I don’t have polka dotting. I would think you would want to fully saturate, so water longer, rather than with greater frequency. I think this is considered more efficient.


I increased the watering duration a week ago and I’m already seeing the spotting going away. My soil type must not allow the water to travel horizontally through capillary action as well.