Maximum Height of Spray Problem

Discussion in 'Irrigation' started by Critical Care, Aug 17, 2005.

  1. Critical Care

    Critical Care LawnSite Bronze Member
    Posts: 1,654

    I need some help on determining the maximum height of spray coming from a nozzle. So far I haven’t seen charts that show this information and so it seems as if perhaps a bit of math may be necessary.

    I have to redo and rethink an install design where there are a number of fruit trees within a lawn area that will be irrigated. Problem being is that the owners don’t want all of the fruit blossoms knocked off from the spray. The bottom branches of these trees are about six feet high, and my original plan called for I-20 heads with standard nozzles.

    The largest I-20 nozzles used would be 3.0s @ 50 psi to cover several 38’ radiuses, and the trajectories from these standard nozzles are 25 degrees. With a little trig, I see that a straight line at 25 degrees extending out to 38’ would reach a height of almost 18 feet, but of course at some point along that line the water drops back down and that maximum height is never reached. So… you calculus experts, can you figure this? What’s the formula?

    The low angle nozzles have 13 degree trajectories, and I may have to go with them, but because of the limited nozzle set available and because of the nature of the layout, these would complicate the design work... but perhaps not quite as much as going with a gazillion fixed spray heads.
     
  2. Wet_Boots

    Wet_Boots LawnSite Fanatic
    Posts: 48,017

    Formula schmormula, the height-of-spray information should be in a catalog. Call Hunter tech support if you don't have it. Regular nozzles are out. Figure a ten foot height with them. You will probably be okay with low angle I-20 nozzles, since Toro lists a 15° S700 nozzle with a maximum height of 5' 7" (for a 4.5 with others spraying less high)
     
  3. Dirty Water

    Dirty Water LawnSite Fanatic
    Posts: 6,794

    You'd be just fine with low angle nozzles.
     
  4. bicmudpuppy

    bicmudpuppy LawnSite Silver Member
    Posts: 2,781

    The PGP low angle set is fairly complete. Any chance you could scale back to PGP's? And this is one instance I won't preach that CR500. They have added a low angle set, but it lacks for sizes and with the extra initial pop up height, it ain't going to be pretty.
     
  5. Wet_Boots

    Wet_Boots LawnSite Fanatic
    Posts: 48,017

    Hopefully, the I-20 low angle nozzles are better than the PGP's. The early PGP low angle nozzles weren't much to brag about, and I would only use the #4 - The humble Toro S700 has it all over the Hunters and their clones for good low angle performance, because of the nozzle assemblies are true low angle, instead of a 'cockeyed' opening in a nozzle set in a 25° trajectory passageway.
     
  6. Critical Care

    Critical Care LawnSite Bronze Member
    Posts: 1,654

    Not long ago I tried some PGP low angle nozzles in an attempt to correct a spray situation at one place, but I wasn't at all pleased with the performance. It may of been that the flow on that zone was maxed out, but even with the smallest low angle nozzle it did nothing more than shoot out a single stream of water. Not good. Should I conclude that these low angle PGP nozzles will always do that?

    I'm going to flag the area today and see where problems could arise. Hopefully I'll be able to get around from having to use all low angle nozzles.

    Okay, my client just said that he watched some PGPs that I installed next door to him and said that the spray height was only about six feet. Six feet, eh? I think some of those were #7 nozzles. Needless to say, I'm still worried about wiping out his fruit trees, although he has now said that he's not concerned.

    Wet Boots, that makes sense about the Toro low angle nozzles, and if you compare the low angle Hunter PGP nozzle to the standard one, you do see that the face of it is angled down to compensate for that standard 25°. But then what is "true" low angle? What's to say that you can't achieve good low angle results by even deflecting water off of a horizontal plate?
     
  7. Wet_Boots

    Wet_Boots LawnSite Fanatic
    Posts: 48,017

    The water in the Hunter is guided through vanes set at 25° in a passageway at the same angle. Then comes the 'cockeyed' nozzle with its abrupt change of direction. Not all that good. They tried that with old brass impact heads, with reduced performance. Since each Toro S700 nozzle includes the passageway the water runs through, there isn't any change of direction, and the nozzles throw the same patterns, at whatever trajectory is built into the nozzle body. When I know there is specific need for low angle performance, I'll often choose the S700 over Hunter. The Rainbird R-50 is also available in a low-angle version that has a 13° nozzle opening, and it gives good spray patterns, too.
     
  8. bicmudpuppy

    bicmudpuppy LawnSite Silver Member
    Posts: 2,781

    Somebody made a rotor with a trajectory adjustment, but I can't remember who. Possibly Toro, maybe that EZ adjust head? Toro rep gave me a case of them when I was starting out 4+ years ago on my own. Never had any call backs on them, but they were pricey. Seems like 12-13 bucks each. But w/ twenty free ones.......Think there is still one or two down in the garage.
     
  9. Critical Care

    Critical Care LawnSite Bronze Member
    Posts: 1,654

    Yeah, those rotors with the variable trajectories had problems with leaking too, didn't they?

    And, guess what... Duh... in the back of Hunter's catalog they have a full page on height of spray. Well, what'ya know. It says that the I-20 3.0 nozzle @ 50 psi has a max height of 10 feet at a distance of 28 feet.
     
  10. Critical Care

    Critical Care LawnSite Bronze Member
    Posts: 1,654

    Started the install yesterday. Man, this design sure took a long time to work out. Had to use short radius nozzles, low angle nozzles, and standard nozzles, and then on top of that try to get a precip rate down correctly in the right areas.

    Now get this... and I'm not using these nozzles, but Hunter states that both of their 2.0 18' short range and 3.0 25' short range nozzles have a height of spray of only ONE foot! One foot??? I wonder how well a 25' nozzle is going to work with a spray of only a foot height? I'll have to pop one of these buggers into a head just to see what it does. Sounds like skipping rocks on water. The trajectory of the 3.0 LA is 8° and the 2.0 LA is only 3°.
     

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