Designing A Drip Irrigation System


#1

I’m in the process of re-doing the plantings around my house and I’m looking into installing a drip irrigation system.

I’ve attached a sketch of what it’ll look like and am wondering how folks would zone things if it were theirs?

The large circles are trees, the medium ones are various shrubs and the smallest ones are various small flowers; the top of the sketch is west-facing

I have 6 zones free on my Iro and not quite sure how to best proceed. One sprinkler installer says that he’d zone it by proximity such that I might have 3 or 4 zones (south side, west side, north side, island)

Thoughts?


Exact water usage using flow
#2

I’m no expert on this, in fact I still have a lot of questions myself using the zones for drip irrigation, but from experience, I can tell you that you really do not want to mix any annual flowers in with your trees or shrubs watering schedules. I have a mix of perennials and annuals in my drip zones, and I have to set the watering to my annuals needs or they wilt/die from lack of water. Because the roots are so much deeper on shrubs/trees, they do not need to be watered nearly as often as the flowers do.

In my case, I’ve had to take care of watering the annuals/perennials with the drip system and leave the shrubs that were put into my drip zones pretty much to what Mother Nature provides them. (Oh, and I’m being stubborn and trying to do this with Flex scheduling for my drip zones.)

Right now, I’m stuck with what I have. I would love to doing it fresh from the start like you!!!

I’m really interested in hearing what others have to say about designing yours!


#3

Hi Linn

I don’t believe that we will have any annuals in our beds since we discussed not wanting to have to re-plant anything year by year…

Now, my soil is very sandy so I don’t know if that diminishes any needs to water trees less frequently; after all, if the water just drains, there won’t be any water down below for the deeper roots to go after, right?


#4

Hi everyone

So my new drip irrigation was installed earlier today; we ended up doing 4 zones

  1. Left Bed
  2. Top Beds Along Deck/Patio & Island
  3. Right Bed
  4. Trees

Now to figure out each zone’s precipitation rate!


#5

So I went out yesterday and tried to get some measurements to determine each zone’s effective area…

I ran each zone for 1 min and noted the water meter reading before and after

I’m using Netafim Techline CV with 0.9 GPH emitters and 12" spacing


Pretty much every shrub or tree has a ring around it - I measured diameter of each ring and totaled them up

My trees seemed like a good place to start since there are only a few of them

Each tree has an ~24" diameter ring around it => this yields an area per tree of 3.14 square feet, based on (Pi * (24/12)^2 / 4… with 4 trees, this gives me an area of 12.57 square feet and I measured a flow rate of 1.11 GPM which seems to yield of a precipitation rate of 8.5 in/hr


Could that be right? That seems awfully high, no? Am I doing something wrong?


#6

How did you get 1.11 GPM ? I come up with ± 0.36 GPM.


#7

I recorded the reading on the water meter before and after…

Also, I didn’t mention this earlier but each tree has a double ring around it…

One thing that was interesting - I ran the zone again for 10 minutes and the flow rate was different; instead of 1.11 GPM, I got 0.862 GPM…


#8

@jsurpless, good detail to note. Are the two rings the same diameter or is one larger or smaller than the other? i.e. Does it look like a Target logo? (with the tree being the center circle) and two 24" diameter rings?

Or the shooting target below with the tree also the center circle)?

Did you run the tests at the same time of the day? Sometimes this can occur if/when your water main is experiencing heavy use and the pressure is less than normal.

I calculate your precip rate as follows:

PR = (96.25(A*B))/©

96.25 = constant that converts gallons per minute (GPM) to inches per hour. It is derived from 60 minutes per hour divided by 7.48 gallons per cubic foot. times 12 inches per foot.
A = #heads -or- #emitters
B = flow rate (GPM) per head -or- emitter
C = zone square footage

A = 2
B = 0.9 GPH = 0.015 GPM
C = 4 (given 24" diameter rings x 2)

PR = (96.25(2*0.015))/(4) = 0.721875 = 0.722 in/hr

I use 4 for the square footage since each emitter is spaced 12" in-line with the Netafim drip tube. Since drip tube is a source point application and not watering the entire area it’s covering, square footage measurements should be considered more of a perimeter calculation.

Hope this helps :smile:


@ronjonp, we get the same thing provided only one 24" ring per tree. :wink:


#9

I usually assign an arbitrary coverage area per emitter then multiply by number of emitters … .but even this is just a WAG. :grinning:


#10

It’s more like the Target logo

I don’t quite follow this - if I have 2x 24" diameter rings, wouldn’t the perimeter of each ring be ~3.14159 * 24" = 75.4"?

So that would mean that I have about 6 emitters per ring, right?


#11

@jsurpless, you’re correct. I was using diameter instead of circumference…let’s blame that on my brain falling asleep :sleeping:

As such, we’ll have 12-13 emitters then per tree if you have two rings.

Let’s recalculate:

PR = (96.25(A*B))/©

96.25 = constant that converts gallons per minute (GPM) to inches per hour. It is derived from 60 minutes per hour divided by 7.48 gallons per cubic foot. times 12 inches per foot.
A = #heads -or- #emitters
B = flow rate (GPM) per head -or- emitter
C = zone square footage

A = 13 ((3.14 * 24") = 75.4"/12" = 6.25 emitters/ring x 2 rings = 12.5 emitters; rounding up to 13
B = 0.9 GPH = 0.015 GPM
C = 3.14 = ((π/4) × D^2) = ((3.14/4) * (24"^2)) = 452.4 sq inches / 144 sq inches = 3.14 sq ft

PR = (96.25(13*0.015))/(3.14) = 5.977 = 6 in/hr

This makes more sense given the inputs. Guess third time in the charm :wink:

Let me know your thoughts.


#12

Hi Emil

That’s actually lining up pretty well with what I observed when I ran it for an hour…

I recorded 48.4 gallons being used in that hour and with the same area you calculated, I got a precipitation rate of 6.18 in/hr

So I tried configuring an ‘Emitter’ nozzle with 6.18 in/hr rate but it doesn’t seem to like my rate - it says it must be 0 < rate < 20 which it is but it doesn’t take my entry - any thoughts?

Now, I have to figure out why my usage varied so much for 1 min vs 10 min vs 60 min - I have a call into Netafim so I’ll have to see what their thoughts are…

p.s.

Hope that you’re feeling better after sleep :wink:


#13

@jsurpless, hmm that is odd, I just tried to recreate this and was able to save a custom nozzle with a precip rate of 6.18 in/hr (on iOS). Double check your nozzle type and make sure you’re using an emitter. Turf nozzles (fixed spray head, rotor head, & rotary nozzle) are maxed out at 5 in/hr. Let me know if this does the trick. If not, please let know what version of the app you’re using.

Keep us updated. I’m interested to know the outcome.

Thanks. Naps are becoming a favorite hobby of mine :relaxed:


#14

Hmmm, interesting - if I type a value and then click off OR click the check mark (presumably, to validate) - I get the error but if I hit Save, all is well…

Here’s a question - my landscaper told me to water the trees for 1 hr every day - this seems rather excessive, given my output flow rate of nearly 50 GPH… before we installed the irrigation, he told me to put down 5-10 GPD…

I made my change to the nozzle for ‘Trees’ and a NEW Fixed Schedule only wants to water for 5 min… this seems kind of low since i thought you’re supposed to water much longer with drip?


#15

Are you using iOS or Android? I’d like to try and recreate this – sounds like it might be a bug.

Just for clarification, your landscaper recommended an hour a day with the current setup?

I assume this was for hand watering?

There’s a number of factors that go into this equation and recommended watering duration. The nozzle/precip rate is used for calculating the time duration – however the root zone depth and soil type determine the actual soil reservoir that needs to be filled. I’ll take a look at your account to see if anything jumps out at me.


#16

I am using the latest version of iOS

Yes, that’s correct

Yes, that’s correct…


#17

I spoke to Netafim and they were rather surprised at how high my precipitation rate was…

They told me that it’s better if the surface area represents the area that the water spreads to; I’ll have to look into that at some point…

They also commented that rings should be further out from the tree, more than the 12"; based on that, I widened the rings as much as I could, ending up closer to 20" radius…

Having done that, my 48.4 GPH over 33.25 sq ft => 2.34 in/hr


I started looking into how much water my trees need - the first one (kwanzan cherry) needs 0.5 to 1.0 in/week

How can I configure Iro to reflect this?

Thanks again


#18

@jsurpless, I agree. I assume 1 emitter will spread to at least 1 square foot – if it’s more, than we can adjust it accordingly.

I didn’t think of this, but also a good point. Depending on the type of tree you have (and how old it is), you want to water out to the drip line of the tree. Obviously on a new tree this is limited to the root ball – but watering outside of it will attract the roots to grow outward in search of water.

Just curious, did you add additional drip line; or emitters? 13 emitters per tree? Are you running Netafim for the entire drip line, or only around the diameters of each trees?

Hmm, good question. We don’t have a simple way of doing this at the moment besides crunching the numbers and overriding the schedule. In theory, we calculate this amount for each zone, then the Iro refills said amount. When you mention, “the first one”, do you have other types of trees with different watering requirements on the same zone?


#19

I have two Kwanzan Cherry, one Autumn Glory Maple and a Magnolia… all are brand-new, just installed but their root-ball is fairly substantial - the trunk is about 2" in diameter, I’d say?

Given that they are new, is it OK to water beyond the root ball?

I just widened the what was there - basically, the installer had wrapped a long length of tubing into two concentric rings - I just widened them such that it was more or less a single ring, as much as possible anyway…

The # of emitters varies by tree and ranges from 10 to 16 emitters

**** EDIT ****

We’re running “blank” Netafim tubing between the plants and trees, using the tubing with emitters only around the plants… in addition, the installer also used some more “heavy-duty” when appropriate as such as going under the lawn or other areas where lots of weight might occur…

**** EDIT ****

Yes, I have three different types (Kwanzan Cherry, Autumn Glory Maple and Magnolia); though, not sure of their watering requirements as of yet…

So right now, the only way to put down a fixed amount of water is to monitor it manually and adjust accordingly? Is there no way to adjust the zone attributes and set up the “bank account” for 1" in some way?


#20

@jsurpless, yes, but make sure the root ball is getting water too. I always used the 80/20; 80% on root ball & 20% beyond it to start, then work to 50/50 over a month or two – keeping an eye on the tree for signs of stress. Too much water isn’t good either as it can suffocate the tree from getting the proper amount of oxygen it needs.

Is it safe to assume these are the only 4 trees on this zone?

We should double check to see if all of the trees need 1" per week for your area. If they are different, it will be harder to determine a watering duration that’s makes everyone happy; think goldilocks and the three bears…what might be right for one tree, could be too much or little for another tree.