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Flexible or Fixed Arm Riser for 3/4" Rotors

Discussion in 'Irrigation' started by surge, May 25, 2005.

  1. surge

    surge LawnSite Member
    Messages: 21

    I was going to use my toro funny pipe to make a flexible arm to connect the main lines to the sprinkler heads(Hunter I-20's). That is until someone told me that I should use a fixed arm riser instead for 3/4" inlet rotors. I am assuming this is because the riser pipe for a fixed arm is 3/4" while a flexible pipe is 5/8". I was wondering what you guys think on this.
  2. Dirty Water

    Dirty Water LawnSite Fanatic
    Messages: 6,794

    Use generic 1/2 barb to 3/4" threaded marlex fittings, and a roll of bulk swing pipe.

    Tell the guy who told you to hard pipe risers to keep doing that, so you can come back and fix the pipe when a careless landscaper hits it.
  3. surge

    surge LawnSite Member
    Messages: 21

    Thanks for the input, although I think I mis-spoke. I guess I meant a fixed swing joint versus a flexible swing joint(funny pipe). Fixed swing joint being schedule 40/80 pipe connected to two threaded ells on both sides so it can still move and not break. As noted I would prefer to use the 5/8" funny pipe tubing, but I am curious if I am going to have flow or pressure problems if I am feeding a 3/4" inlet rotor with a 5/8" flexible pipe.
  4. bicmudpuppy

    bicmudpuppy LawnSite Silver Member
    Messages: 2,781

    how long a run of swing pipe? are you dealing w/ low pressue? are you using large nozzles? If you using less than 3' of swing and your pressure isn't a problem, and you aren't using nozzles designed to exceed 6 or 7 gpm........don't sweat it.
  5. surge

    surge LawnSite Member
    Messages: 21

    The swing joint will be 1' to 2' max in length.

    Here is my setup.

    Meter to House: 3/4" PVC
    Pipe from Valves to Heads is 1" PVC
    Static psi: 70 (PSI at 1/2" hose bib on main line entering the house)
    Flowrate: 10 GPM (Givin 3/4" PVC main line and 70 psi from online info I found)

    Heads: Hunter I-20 (using 2.0LA nozzle)
    Head consumption rate: 1.6gpm
    inlet size: 3/4"

    I have alot of toro funny pipe left over from a previous install along with the male 3/4" funny pipe elbows. The funny pipe is 5/8" in diameter. What I would like to do is use a 1" (S) to 3/4" (Threaded female) elbow to connect onto the main line. Then use the 3/4" male threaded to 5/8" barbed funny pipe elbow to screw into the pvc elbows. Then connect about 1-2 feet of 5/8" funny pipe, then connect another 5/8" barbed to 3/4" male threaded funny pipe elbow to that which then gets screwed into the I-20 head.

    Logic says I should be fine but I thought I read somewhere that funny pipe should not be used for rotor/gear heads, although it didn't say why. I can't find that article right now, but they said instead you should create a 3/4" fixed swing joint as noted in my above post using 4 threaded elbows and sch 40/80 pipe.

    Let me know what you guys think.

  6. Wet_Boots

    Wet_Boots LawnSite Fanatic
    Messages: 50,243

    You have to go way beyond that nozzle for that 3/8 ID pipe to make a difference. There are pressure loss curves you can examine to confirm this. Almost nothing used in a residential installation would suffer from being fed from funny pipe.
  7. drmiller100

    drmiller100 LawnSite Senior Member
    Messages: 562

    is the hole in the center of the nozzle smaller then a half inch funny pipe??????
  8. bicmudpuppy

    bicmudpuppy LawnSite Silver Member
    Messages: 2,781

    The #10 nozzle is less than 3/8". Let me see you feed IT w/ 2' of funny pipe and normal (less than 50psi) pressure.
  9. Wet_Boots

    Wet_Boots LawnSite Fanatic
    Messages: 50,243

    Why would you run a #10 at less than 50 psi in the first place? :) A call to Hunter tech support got me a comment in this vein some years back. I was renovating a system, to add coverage to existing zones, and the Hunter heads (with nozzles smaller than a 10, to be sure) weren't spraying far enough. The static pressure was 50 psi, and the expanded zone ran in the mid-thirties. Turns out this was the year that Hunter changed their nozzles, and one result was lost distance at pressures under 50 psi. [Well, you want to be running with at least 50 psi head pressure anyway, says the tech] Good thing I had a supply of old nozzles to restore the distance I 'knew' they should be spraying.
  10. bicmudpuppy

    bicmudpuppy LawnSite Silver Member
    Messages: 2,781

    Yeppers, them "new" hunter nozzles are the Best :)

    50psi at the head means a static of 65? or 70+ if your in RP country? I see a whole lot more 55-60psi than I do 70+, that probably explains why I'm not the greatest PGP fan out there. My CR500's will pop and shoot w/ 30psi head pressure (and maybe even "funtion" w/ 25)

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