Catch cup guided process

Continuing the discussion from Frustrated with Iro:

I agree, I think we can do some great work around calculating precip, creating you a custom nozzle, all through a simple walk-through process. My ultimate goal to make fine tuning your system as easy as possible.



Maybe your blog post you are planning will be a start to this?

Found a handy calculator at

The best and easiest way would be to have a connected flow meter. With the actual zone square footage, the the ideal watering time is easy to calculate.

This is a great find!


Just a data point – unless I’m doing something very wrong or the calculator is way off, my Hunter rotors are coming in between .25 and .5 inches per hour. That’s far below the 1 inch default. I wouldn’t say my system was exceedingly well designed, but I’m getting those numbers in 5 zones I tested with Orbit catch cups. Fixed spray heads in 2 other zones were close enough to the default 1.5 inches per hour.

@msdowdie, I assume these are MP Rotators? They do have very low precip rates, so this is possible.

This is the precip rate for rotors, which are a little different than rotary nozzles…do you think you maybe had these improperly selected?

Hope this helps :smile:

Best, Emil

Don’t want to thread jack this but I do have an observation about catch cups that may be helpful to others. I picked some up and ran a test on my zones and found out a couple of things.

First I found out that two of my zones have more overlap then I thought. I originally ran the test not expecting an over lap in those zones. The two zones are different heads. One is fixed spray the other is rotor head. I did the calcs and came out with higher then average flow rates on the zones. Then I was rereading the orbit directions and noticed the section on overlapping zones. they said that you should place the cups out to cover both zones. Then run zone 1 for ten minutes. Then take the cups that were empty and move them to zone two basically and run zone two for ten minutes. That is zone ones reading. Put the cups back and run zone 2 and then move zone one cups and run zone one again. That is zone 2s reading. When I did this test the flow rate numbers were cignificantly less. Almost half of running the numbers the other way. The official way doesn’t pass my eye test. I’m going to err on the side of caution for a week or so and go with the higher flow rates. I guess my observation is that if you have overlapping zones you may have to make a judgement call and it may be best to run the test a couple of different ways and do your calculations as there was a huge disparity at least for me. I can only attribute this to low numbers throwing off averages in the calculator mentioned above.

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Thanks for helping out the community, I hope more people bring this passion to understand how their system works :wink:

@emil, thanks for getting back to me on this. I definitely have Hunter rotors (as opposed to rotators). I think they are PGP rotors, but will have to verify when I’m home. The PGP rotor specs show precipitation rate of .4 inches per hour which is more in line with my observations using the catch cups.

@msdowdie, I assume these numbers were calculated from a catch cup test? Sounds like your head to head coverage is impacting the results as you have some areas with heavier coverage than others. Also, what time of the day did you perform the test? During your scheduled watering time? Sometimes the water pressure can vary depending on the time of day and demand for water in your neighborhood (i.e. how many other systems are running at the same time).

Hope this helps.

Best, Emil

I put some Orbit catch cups earlier today and got some measurements…

Not quite sure how to convert the volume in each one (in ml) to a precipitation rate (in/hr)?

This is a pretty slick tool, let us know if you have any questions regarding using it.

Very slick, indeed!

I still have more thorough testing to do as I have had some inconsistent results but it seems that my zone is putting down around 0.4 in/hr which seems to be in line with the Hunter PGP-ADJ specs for Nozzle RED4… their spec only goes to 60 psi but I believe I have higher (builder said 80 psi, I think, and we have a reducer on the domestic side down to 60 psi but not on irrigation)

If I am correct, the rotor head nozzle has a rate of 1.0 in/hr?

@jsurpless, correct. Our default precip rate for rotor heads is 1.0 in/hr.

You might have an efficiency issue. This resource is great for evaluating sprinkler system uniformity (referred to as efficiency in your advanced settings)

Hope this helps :smile:

Best, Emil

Getting more and more into the weeds now with my Rachio. Planning to get some Orbit Catch Cups (call me lazy, as I feel it is easier than using tuna cans or similar).
I can see it makes sense especially for lawns. I assume I need to place a couple of them per sprinkler I have in that zone? So if I have 3 sprinkler heads per zone, I should use around 9-12 cups for the whole zone?

For other scenarios which are not lawn but an area that has a couple of plants only, I have setup to water to the plant itself as much as possible. Should we just put the cup where the sprinkler waters the plant? Obviously the area between the plants does not get watered very well, but again there is just mulch in between.

Wondering if you have any suggested on that rather odd zone I have with multiple separated areas with weed barriers and rocks on top and each has 1 small palm tree (no idea its name).

Unfortunately part of that zone is another area that has a tree (very forgiving in term of low and or high watering) and some small plants and using dripping there. What’s the best way get that setup as I certainly do not want to over water them. Maybe best to set that zone into a fixed schedule?

I think a fixed schedule makes the most sense for odd groupings of crop types :wink: