# First "Tuna Can" Test



## Lambo (May 21, 2018)

Currently in Kansas it is HOT. Mid-90s everyday until forever...it seems. This evening, once it cooled down, I laid some crabgrass preventer (contains prodiamine) and some Earth Right soil conditioner.




Excited to see what the Earth Right stuff does because my yard is dense, sticky clay not far down into my soil. I used double the normal application rate (per the instructions) because this was my first application. Normally a quart covers 10,000 sq ft. I used 1.5 quarts on my 7,500 sq ft lawn. Hopefully aids in water getting to my grass roots and to get rid of some soggy spots that appear at the end of my buried gutter lines in the back.

Both products I laid down this evening needed a thorough watering in. This was a great time for me to do my first tuna can test. I didn't have any tuna cans laying around, but I did have these small plastic containers my wife uses to take salad dressing with her lunch. I laid a total of 30 of them around my yard and ran my 6 zones for 20 minutes each. I generally keep a nice yard, but this is my first spring with an irrigation system, so I aiming to adopt the 1" of watering per week.

Results:
These are only some of the cups. No need to show you all 30 cups with water in them.




I measured and recorded the results by area of my lawn. I really regret not taking extra time to determine what heads were lagging, but that can be later.



I had 14/30 with 3/16" of water in them, so that was promising, but I also had 5 cups with 1/8" and 2 cups with 3/8". The average for my entire yard tonight was .2104" on 20 minutes. In order to hit 1 inch of water in a week, I will really need to run the system for a long time! At this point, I would need to run each zone a little over 1.5 hours a week to hit 1". 6 zones x 1.5 hours =9 total running hours per week. Seems excessive to me, but I am a rookie. How long do each of you run your sprinkler systems each week?


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## g-man (Jun 15, 2017)

1.5 hr per zone is about normal. With Hunter mp I run 1.2hr per zone.


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## Delmarva Keith (May 12, 2018)

Exact typical average is 79 minutes and 42 seconds per inch :lol:

Jist kidding. I agree with g-man - around 1 to 1.5 hrs for an inch is typical.


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## kolbasz (Jun 7, 2017)

Delmarva Keith said:


> Exact typical average is 79 minutes and 42 seconds per inch :lol:
> 
> Jist kidding. I agree with g-man - around 1 to 1.5 hrs for an inch is typical.


thats crazy. I think it is long when I go 30 minutes per zone on my maxipaws. I could only imagine the system running for 6 hours. 4x1.5


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## g-man (Jun 15, 2017)

Kolbasz, the max you could get from the maxi paw system is 1.2in/hr. I can't see how you could get 1in in 30min. Have you done a tuna can test?


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## kolbasz (Jun 7, 2017)

g-man said:


> Kolbasz, the max you could get from the maxi paw system is 1.2in/hr. I can't see how you could get 1in in 30min. Have you done a tuna can test?


No, it is on the list. I guess I was just trusting rachio. Maybe rachio is cheating me and 1 hour per would be more accurate, if I was to go by the default blue tip, which is what I believe I have (it is default).


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## g-man (Jun 15, 2017)

Rachio doesnt know your system. You pick spray nozzles, but then in advance settings, you adjust the precipitation rate for each zone (based on the audit or the water meter method).


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## kolbasz (Jun 7, 2017)

g-man said:


> Rachio doesnt know your system. You pick spray nozzles, but then in advance settings, you adjust the precipitation rate for each zone (based on the audit or the water meter method).


I thought I set that up, but it is worth a second look based on this discussion


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## kolbasz (Jun 7, 2017)

Just looked. Likely an issue is that I have this set to 1" per hour. Explains a bit for my timing.


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## g-man (Jun 15, 2017)

Do the audit/tuna test and set each zone to the audit/tuna results. I keep my allowed depletion to 50%. If it it too hot in the summer I change it to 40% (less water, more frequent). Other than that, the rest should all work in the rachio.


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## Lambo (May 21, 2018)

After a brutally HOT week, nature went and totally redeemed itself! This was not in the forecast earlier today.


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## kolbasz (Jun 7, 2017)

g-man said:


> Do the audit/tuna test and set each zone to the audit/tuna results. I keep my allowed depletion to 50%. If it it too hot in the summer I change it to 40% (less water, more frequent). Other than that, the rest should all work in the rachio.


Might need to talked this through a bit more.

If I spray head to head at .5" per hour, is that not 1" total? Or are the true numbers in the tuna can as opposed to what the head theoretically gets?

What is allowed depletion? Mine is currently at 50%

Anything else I should be looking at?


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## Delmarva Keith (May 12, 2018)

kolbasz said:


> g-man said:
> 
> 
> > Do the audit/tuna test and set each zone to the audit/tuna results. I keep my allowed depletion to 50%. If it it too hot in the summer I change it to 40% (less water, more frequent). Other than that, the rest should all work in the rachio.
> ...


True numbers come from an audit - put out the cans and see what you actually get per hour. Theory is a great guide but actual water on the ground is the only truth.

Allowable depletion is the amount of water left in the soil after the plants and sun are "allowed" to use it, before the irrigation system will add water. Basically how dry are you willing to allow the soil to get before it gets watered. It starts with soil field capacity - basically the amount of water the soil can accept before it just runs off and won't accept any more, and after the moisture has slowed moving downward - that will be the 100% mark. If you think of the soil as a sponge you are holding and pouring water on it, field capacity is reached when it's so full of water that pouring more water on it runs off of it, and after any excess water has spilled out of it from gravity. Field capacity is based on the soil type you entered. When you set allowable depletion you are setting how much of that 100% is still "left" in the sponge before irrigation will add water. 50% seems high to me for a lawn but if it's doing well and not overly wet, I guess that's fine.

The crop coefficient is the amount of water your "crop" uses compared to a reference crop of short mowed cool season turf grass. The number you set here will be based on things like your grass type, mowing height, amount of shade, crop vigor, allowable depletion (there it is again) and its effect on crop ET, etc., etc. If the machine set it at 80%, I'd hesitate to mess with that. If everything was going great and then with a temp / sunlight change it suddenly got too wet or too dry, I'd consider adjusting it (an increase in the crop coefficient will tend to have the machine irrigate more as the reference ET increases, lowering it will irrigate less).

Efficiency relates to how uniform the irrigation is over an area. You can get an idea from your tuna can audit. If all the cans are equally full, your efficiency is higher. If you have dryer spots, your efficiency is lower. The ratio between the cans is the efficiency.


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## TC2 (Sep 15, 2017)

kolbasz said:


> If I spray head to head at .5" per hour, is that not 1" total? Or are the true numbers in the tuna can as opposed to what the head theoretically gets?


When you look at the inches per hour, it usually has a square or triangle above. This is for square and triangle head layouts, so if it says 0.5" per hour below one of these, that is already accounting for head to head coverage. For rotors it will usually state that it's for 180 degrees of rotation. A 90 degree rotor puts down 4x as much water on a given area than a 360 deg rotor.


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## kolbasz (Jun 7, 2017)

TC2 said:


> kolbasz said:
> 
> 
> > If I spray head to head at .5" per hour, is that not 1" total? Or are the true numbers in the tuna can as opposed to what the head theoretically gets?
> ...


what is meant by square and triangle layout? My front yard is squarish, my heads are laid out 3-4-2, the 2 is because there is a flower bed in the corner.

The 2 corners of the 3, do 90 degrees, the 2 middle of the middle 4 do 360 degree and the rest do 180 degree.

So then I suppose, something doing 360 will put less water in a given spot that if it did 180 and was hitting the same spot and even less than the 90.

This then helps me to better realize why auditing is important. Although they are all putting out the same flow, their actual in./hr in a given spot will vary by the pattern.

So do I audit per zone or by area? I assume zone, to know what each zone is putting out and then put that into Rachio. But then I wonder there, how rachio knows what areas are overlapped to know how to calculate what each zone needs to put down.


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## TC2 (Sep 15, 2017)

kolbasz said:


> what is meant by square and triangle layout? My front yard is squarish, my heads are laid out 3-4-2, the 2 is because there is a flower bed in the corner.


I believe it's like an average. The area in the square gets the given amount if the rotors travel 180 deg.

What you can do is alter nozzles to reduce water output from 90 deg rotors and increase it for 360.

MP rotators take the angle problem out of the equation and I guess that's where most of the water saving comes from.



> So do I audit per zone or by area?


You'd essentially have to figure out what part of the zone gets the least water and take that as your baseline to ensure everywhere gets what is needed.


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## kolbasz (Jun 7, 2017)

TC2 said:


> You'd essentially have to figure out what part of the zone gets the least water and take that as your baseline to ensure everywhere gets what is needed.


OK, I think this makes sense.

In my 3-4-2, there are 2 areas, call them a and b

3-a-4-b-2, being the thought. If a needs more water than b, increasing the time on the 3 is better than increasing 4 because increasing 4 means b will also get more water.


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