# Hunter I-20 Performance Test



## TommyTester (Jul 3, 2018)

Lumpy uniformity.

[media]https://www.youtube.com/watch?v=wntXVbRmPtQ[/media]


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## Delmarva Keith (May 12, 2018)

Interesting. I would not have expected that result. Looks like the Rainbird 5004 is still the champ.


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## ken-n-nancy (Jul 25, 2017)

Thanks for making the results of your testing available here -- it's interesting to see the results that you've found.

I was trying to understand the uniformity calculations and noticed that it seems that you excluded some of the samples, at least if I'm understanding the "drop" note on cups 9-13 as shown at time 2:09 (direct link below) https://youtu.be/wntXVbRmPtQ?t=129

I'm curious as to what led you to drop those data points from the uniformity calculation?


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## Green (Dec 24, 2017)

TommyTester said:


> Lumpy uniformity.


Which nozzle set...dark navy blue or medium bright blue? Looks like the latter to me.
Also was the radius adjustment screw hitting the stream?


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## TommyTester (Jul 3, 2018)

ken-n-nancy said:


> Thanks for making the results of your testing available here -- it's interesting to see the results that you've found.
> 
> I was trying to understand the uniformity calculations and noticed that it seems that you excluded some of the samples, at least if I'm understanding the "drop" note on cups 9-13 as shown at time 2:09 (direct link below)
> 
> I'm curious as to what led you to drop those data points from the uniformity calculation?


The industry defines Distribution Uniformity % as the average of the volume of lowest quarter of cups divided by the average volume of all cups. This implies we have to use a test with 8/12/16/20/24 cups with the lowest Quarter being 2/3/4/5/6 cups. Usually the cups are set-out in a matrix covering a multi-head area/zone to find the DU% and tweak heads accordingly. I've adopted the methodology as a standard for single head tests just to be consistent although it isn't a perfect method.

When I run a test I don't know the range ahead of time. If the results show it covers the first 8 cups fairly well but drops off quickly before 12 cups, I use just 8 in the DU% calculation. If the results show it covers 12 cups fairly well, I use all 12 cups in the calculation. What I don't like about using this method is so many of these sprinklers over-water the first 2-3 cups forcing the DU% to be lower than it would be otherwise. The DU% is designed to identify poor coverage, so areas that are over-watered are by definition "well covered." That is why showing the graph is helpful. It shows where water is being wasted and where over-watering problems might surface.


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## TommyTester (Jul 3, 2018)

Green said:


> Which nozzle set...dark navy blue or medium bright blue? Looks like the latter to me.
> Also was the radius adjustment screw hitting the stream?


The stock factory installed 3.0 Blue nozzle. Diffusion screw was retracted and did not interfere with the stream.


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## ken-n-nancy (Jul 25, 2017)

TommyTester said:


> ken-n-nancy said:
> 
> 
> > I was trying to understand the uniformity calculations and noticed that it seems that you excluded some of the samples, at least if I'm understanding the "drop" note on cups 9-13 as shown at time 2:09 (direct link below)
> ...


OK, I understand your rationale. However, I'll mention three items:

A - I think you could still compute the DU% with an odd number of cups. Inclusion of more points gives a more accurate result, as having fewer cups magnifies the effect of any outliers. I would do this by pro-rating the inclusion of the "least outlying" of the "lower Q" of cups appropriately.

B - In particular, in this specific situation, by dropping cups 9-12, you are removing some of the more uniform portion of the coverage region of this particular sprinkler. Inclusion of those cups gives a better DU% for this test:
Avg of Cups 1-12: 15.83
Avg of Lower Q (5,6,12): 9.67
DU = 61.05%​
Choice of which cups to "drop" is important. By arbitrarily dropping cups 9-12, you eliminated primarily "normal" cups from the distribution, as none of the "outliers" were in this region. If you had instead chosen to eliminate cups 1-4, you would have had computed a very different DU for this sprinkler. (Which, arguably, from the point below, is probably a better indicator of the DU% of this sprinkler.)
Avg of Cups 5-12: 12.25
Avg of Lower Q (5,6): 9
DU = 73.47%​
C - By using a line of cups instead of a matrix of cups, you have a greater percentage of cups in close than farther away, due to the x-squared aspect of area. This means that compared to results determined with matrix coverage, your tests will favor sprinklers with in-close watering that is near the average delivery, but will give poorer results for sprinklers that deliver too much (or too little) water in close. Having uniformity in the outer half of the spinkler's linear range is actually more important than having uniformity in the inner half of linear range, since the outer half of linear range covers 3 times as much area as the inner half of linear range. (For a sprinkler with linear range of x, the area of the inner half of coverage = (x/2) * (x/2) = (x*x)/4, which means the outer half of coverage is (x*x)*3/4, so the "inner half" covers a quarter of the area, and the "outer half" covers three-quarters of the area.)

I haven't looked through the other videos of sprinkler test results that you've put together to know if the above data analysis effects from "dropping" particular cups exists for all of the sprinklers you've tested, but the particular choice of dropping cups 9-12 really shifts the I-20 performance downwards.

Lastly, please don't take these comments as negativity on your tests - I think it's awesome that you're doing this testing and sharing the results with everybody. As a fellow engineer, however, I couldn't help but comment on these methodology issues, particularly as they have skewed the findings.

Thanks!


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## massgrass (Aug 17, 2017)

Great, I have a lawn full of Hunter I-20's.


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## Bkell101 (Jun 25, 2018)

Delmarva Keith said:


> Interesting. I would not have expected that result. Looks like the Rainbird 5004 is still the champ.


Can't find the review in this one. I thought tommy said the orbit 6 gear one was the best so far?


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## JDgreen18 (Jun 14, 2018)

massgrass said:


> Great, I have a lawn full of Hunter I-20's.


Lol me too. Mine is brand new, I'm going to do my own tuna can test as long as u have good head to head coverage there shouldn't be any issues.
That being said the coverage I get having and irrigation vs using a hose Im already way ahead of the game.


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## TommyTester (Jul 3, 2018)

ken-n-nancy said:


> B - In particular, in this specific situation, by dropping cups 9-12, you are removing some of the more uniform portion of the coverage region of this particular sprinkler. Inclusion of those cups gives a better DU% for this test:
> Avg of Cups 1-12: 15.83
> Avg of Lower Q (5,6,12): 9.67
> DU = 61.05%​
> ...


Points well taken. After doing a number of these sprinklers it's clear the standard DU calculation method doesn't tell the full story. That is why I'm supplying the raw chart which does a better job of showing the distribution uniformity and range..

On this particular sprinkler test, I agree cups 9-12 should be included in the calculation and I will update that in my spreadsheet for future use..

Thanks.


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## Delmarva Keith (May 12, 2018)

Bkell101 said:


> Delmarva Keith said:
> 
> 
> > Interesting. I would not have expected that result. Looks like the Rainbird 5004 is still the champ.
> ...


If I remember right, it's the review of the Rainbird 42A or something like that. Uses the same 5000 series nozzles.


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## Rain Bird Corp (Jun 6, 2018)

TommyTester said:


> Lumpy uniformity.


May I share with this audience how manufacturers test sprinkler uniformity? Our set-up is conceptually the same as yours. We generally do our testing in a zero-wind facility to remove wind as a variable. But we also test single leg distribution (a single string of catchments). Our goal is not to have an equal amount of water in each catchment after the test of one sprinkler. Our goal is to generate distribution rate curve that is in the shape of a wedge or triangle with the most water in the first catchment and the least water in the last catchment with uniformly decreasing amounts in each catchment in-between. This would be perfect uniformity. (Never seen it myself.)

The reason for this is that we (all manufacturers) recommend what we call head to head spacing which means there is another head spraying back toward the first head and also applying water to the study area. Imagine a test set up has 10 catchments. In the first catchment we find 10 units of water after the test, then 9 in the next and so on until the 10th catchment has 1 unit of water. Then, perform the test again, but put the sprinkler at the other end of the string of cans in your yard. Run the test and you should get the same result except since we did not empty the catchments, now every catchment has 11 units of water in it.

Software makes our analysis job easier by allowing us to enter the results of a single test and use different spacing and arrangements of sprinklers to calculate DU, etc.


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## Spammage (Apr 30, 2017)

That makes perfect sense given an ideal layout, and also may explain why the orbit sprinkler designed to be used with a hose has more uniform coverage than the rotors designed to be in the ground.


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## Bkell101 (Jun 25, 2018)

Rain Bird Corp said:


> TommyTester said:
> 
> 
> > Lumpy uniformity.
> ...


great insight thanks!!

why not make it uniform and 5 + 5 for a total of 10 units of water all the way across?


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## Movingshrub (Jun 12, 2017)

Rain Bird Corp said:


> TommyTester said:
> 
> 
> > Lumpy uniformity.
> ...


How does that work with the 15CST and 15EST nozzles? I am unsure what shape you all are expecting those to be laid out in for ideal coverage. All I know is that the short edges, get WAY more water than the long edges, measured equal distance from the sprayer.


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## Delmarva Keith (May 12, 2018)

Rain Bird Corp said:


> TommyTester said:
> 
> 
> > Lumpy uniformity.
> ...


That never occurred to me. Seems obvious now that you've explained it and your explanation is perfect. I feel like a dope with inside the box thinking all these years (or really just lack of thinking through the why to go with the how)  . Always more than one way to skin a cat (and I like cats  ).


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## g-man (Jun 15, 2017)

This is a visual to what @Rain Bird Corp explained. Head to Head coverage is the key to even distribution.










From www.irrigationtutorials.com


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## BmetFerg (Jun 26, 2018)

I really appreciate your sprinkler reviews. I'm not sure If I'm caught up on all your reviews but is the Melnor 3900 still one of the top performers?


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## TommyTester (Jul 3, 2018)

BmetFerg said:


> I really appreciate your sprinkler reviews. I'm not sure If I'm caught up on all your reviews but is the Melnor 3900 still one of the top performers?


 Yes, but also consider the Orbit H2O-Six.


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## TommyTester (Jul 3, 2018)

g-man said:


> This is a visual to what @Rain Bird Corp explained. Head to Head coverage is the key to even distribution.
> 
> 
> 
> ...


That graphic is a bit misleading isn't it? ... as heads are suppose to be arranged in triangles and squares meaning each head could be getting hit from 2 or 3, or in some case even more adjacent heads.

I do have 2 I-20s on hand, I might do a head to head cup test and see how the data comes out as I move them closer together. I could also keep the cups in place and move the I-20 to the furthest wet cup's position.


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## TommyTester (Jul 3, 2018)

Rain Bird Corp said:


> TommyTester said:
> 
> 
> > Lumpy uniformity.
> ...


I can appreciate the challenge of designing and producing a nozzle to do that. May I ask if plastic nozzles degrade over time, and if so, shouldn't precision milled stainless nozzles be offered? Thank you for your input.


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## Rain Bird Corp (Jun 6, 2018)

We do not see significant degradation in plastic nozzles in our severe long term life testing in gritty water. If there ever was, they can easily be replaced. (Go to a wholesale outlet and see if they have some. If not, call 800 RAINBIRD and see if you can sweet talk an agent into sending you some.)

Some think that brass nozzles are superior in this way. The opposite is true. Any amount of grit in the water will erode the soft brass.

We have not used stainless steel due to expense and our opinion that any benefit does not warrant that expense.


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## TommyTester (Jul 3, 2018)

For fun I took my 13 cup Hunter I-20 data and did a Head-to-head estimate in excel using the 60% diameter head spacing rule just to see how it would come out.

Looks good!! I don't see a need to test this now. Great discussion.


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## Rain Bird Corp (Jun 6, 2018)

Bkell101 said:


> great insight thanks!!
> 
> why not make it uniform and 5 + 5 for a total of 10 units of water all the way across?


Rotors rotate through an arc. The amount of area in the arc of the rotor close to the sprinkler (let's say between 1 foot and 2 feet away from the sprinkler and between the edges of a 5 degree section of the arc) is much smaller than the area described the same way except between 49 and 50 feet from the sprinkler. The size of that area close to the sprinkler may be 1 square foot while at 50 feet from the sprinkler the size of the area may be 10 square feet. (Someone else can do the math.) This is good exercise for your 3D thinking skills.

This explains the counter-intuitive effect that even with what looks like a heavy stream shooting out to the end of the radius, the farthest catchment most often captures the least water. The "heavy" stream very quickly passes over that last catchment device and very little water is captured.

In order to get the result you suggest, far more water must be shot 50 feet through the air while also uniformly dropping proportionally smaller amounts as you get closer to the sprinkler.

Theoretically, your idea works(5+5). Making water do that is very difficult. It is still hard to take the approach we do and that I previously described, but easier than this approach. There are also other benefits to uniformity that are gained that are too technical to describe here.

Giving credence to your idea, it appeared to us through testing of our competitors nozzles many years ago that a competitor attempted to take this (5+5) approach. They appear to have abandoned it a few years later.


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## Rain Bird Corp (Jun 6, 2018)

Movingshrub said:


> How does that work with the 15CST and 15EST nozzles?


Not very well. Getting nozzles to spray that shape with high uniformity in mass production quantities at reasonable expense is near impossible. Consider sub-surface in narrow strips if you must have the highest uniformity. For most, the CST & EST nozzles are good enough.


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## Bkell101 (Jun 25, 2018)

Rain Bird Corp said:


> Bkell101 said:
> 
> 
> > great insight thanks!!
> ...


I just wanna say that this is so cool that you are giving us this insight. I mean I'm a total novice and I'm really trying to keep up, but I think it's fascinating! Thanks!


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## Rain Bird Corp (Jun 6, 2018)

Happy to do it.


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## Bkell101 (Jun 25, 2018)

TommyTester said:


> Lumpy uniformity.
> 
> [media]https://www.youtube.com/watch?v=wntXVbRmPtQ[/media]


Where did you purchase that one tommy? It's kind of fun doing this and testing it out at home , going to do my own tests as well


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## TommyTester (Jul 3, 2018)

Bkell101 said:


> Where did you purchase that one tommy? It's kind of fun doing this and testing it out at home , going to do my own tests as well.


Plastic I-20

You'll need a 3/4" to 1/2" adapter like this one if you plan to use a spike.  HERE. I got one locally at Home Depot ... they carry Orbit and some Rain Bird stuff.

Pipe tape will be needed for the 1/2" portion. Have fun!


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## Movingshrub (Jun 12, 2017)

Rain Bird Corp said:


> Movingshrub said:
> 
> 
> > How does that work with the 15CST and 15EST nozzles?
> ...


So in regards to the CST, SST, and EST nozzles, what shape are they expected to be laid out in to provide overlapping coverage? Rectangle strip? Square? Triangles?

To your comment - "Getting nozzles to spray that shape with high uniformity" - what would they cost if I did want them to be in that shape and uniform?

Sub surface wasn't an options for sprigging since I was afraid the sprigs would dry out.


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## Rain Bird Corp (Jun 6, 2018)

Movingshrub said:


> So in regards to the CST, SST, and EST nozzles, what shape are they expected to be laid out in to provide overlapping coverage? Rectangle strip? Square? Triangles?
> 
> To your comment - "Getting nozzles to spray that shape with high uniformity" - what would they cost if I did want them to be in that shape and uniform?
> 
> Sub surface wasn't an options for sprigging since I was afraid the sprigs would dry out.


Most prefer heads alternating on one side and then the other for SST and then an EST on each end spaced so that the side spray of one lands even with the next head. CST would use the same approach. I would use CST only with turf since shrubs would too easily block the spray of CST.

No idea of the cost since we have not tried. We considered it too obviously unattainable.

Understand about the sprigs. Sometimes they are established with temporary overhead irrigation. Not often an option though.


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