Rotor Head Hookup question

Discussion in 'Irrigation' started by turbosl2, Jul 6, 2012.

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  1. turbosl2

    turbosl2 LawnSite Member
    Posts: 56

    I appreciate the help, thank you. I figure i am getting less than 25PSI at the head. I would like to know how to measure it at the head dynamically. I am only putting the 6GPM in the full circles, and i am using 3-4GPM in the 180s 1.5-2s at the 90s.
     
  2. DanaMac

    DanaMac LawnSite Fanatic
    Posts: 13,156

    You must get a pitot tube and gauge. The tube goes in the direct spray of water directly in front of the nozzle. And you will get very wet :)
    Here are some that are available Gauge and pitot tube
     
  3. Kiril

    Kiril LawnSite Fanatic
    Posts: 18,308

    Would that be 50-55 PSI @ 12 GPM (eg. dynamic pressure) or your static pressure? Seems to me you probably designed around a static pressure and now you are having problems with coverage as your nozzle pressures are way below what you need.
     
  4. Kiril

    Kiril LawnSite Fanatic
    Posts: 18,308

    That is pure bull.

    If you don't have the pressure, renozzling is not going to get you the distance .... sorry. Also, your design is a little less than stellar on coverage, even if you did have the correct pressures.
     
  5. Wet_Boots

    Wet_Boots LawnSite Fanatic
    Posts: 47,381

    The thing to do is to perform the flow and pressure tests simultaneously. Put the pressure gauge on your system blowout valve. Or better yet, on the backflow preventer. Open a zone, and read the pressure. Go to the water meter, and determine the flow. Pair those flow and pressure numbers together. Now close off the flow a bit, downstream of the pressure gauge and take a second set of flow-and-pressure numbers. Repeat the flow restricting, and take more flow-and-pressure measurements. You should end up with a table of paired flow-and-pressure numbers. That table is what your water supply really is. Your water supply is not a pressure. Your water supply is not a flow. It is a combination of flow and pressure, and that combination is what you design a system with.
     
  6. turbosl2

    turbosl2 LawnSite Member
    Posts: 56

    I will try this, but will i still need the pressure at the head, or should it be equal inside at the backflow preventer and at the head. What do you think about using the 1/2 swing pipe, is that restricting me or helping me?
    Posted via Mobile Device
     
  7. Wet_Boots

    Wet_Boots LawnSite Fanatic
    Posts: 47,381

    What you need is one thing. What you actually have is another thing. Based on what you've described, you are plain and simple screwed.

    Is the system entirely in place? Every single valve and head?
     
  8. turbosl2

    turbosl2 LawnSite Member
    Posts: 56

    That doesnt really say much. The system has been in place for 2yrs. I am just asking if the 1/2" swing pipe matters. I did some research and i dont think it does because my GPM is never going to exceed 6, and 1/2" or even 3/8" should flow 6GPM (1/2" pipe can flow about 14GPM) It not like the yard is not getting covered. I watched the system when it was all dirt, i was getting decent covereage. It could be that i am just not happy with the close in watering of the rainbird 5004 heads. With the pure sand the water goes right through it, and at the end of the stream i see green, but thats because substantial water falls there, so its not an even distribution.
     
  9. Wet_Boots

    Wet_Boots LawnSite Fanatic
    Posts: 47,381

    The swing pipe only matters to the extent that it can subtract maybe one or two psi. Your system seems to be short by several dozen psi. You will never ever ever ever see any head on your system spray as far as 40 feet.
     
  10. I doubt the funny pipe is the main issue like boots says something else is going on. I wouldn't use funny pipe trying to push 6gpm though. It is a bottleneck in a system that needs minimum pressure loss. 40' is really pushing it. 30-35' max with 5000s in my book. May have to swap them all out to maxi paws.
     
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