Rotor Head Hookup question

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

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  1. DanaMac

    DanaMac LawnSite Fanatic
    Posts: 13,156

    You need to get a pitot tube and pressure gauge and check your pressure at the heads. If you have 50 PSI STATIC at the backflow preventeer, you will NOT have 50 PSI DYNAMIC at the heads. So you will never achieve 47' if you were basing it on 50 psi from the charts, and you started at 50 psi static.
     
    Last edited: Jul 6, 2012
  2. greenmonster304

    greenmonster304 LawnSite Gold Member
    Posts: 3,037

    I think your mistake was taking a gpm measurement and a static pressure reading and not a dynamic pressure reading while doing your flow test.

    If you have the pressure and flow there is mo reason you can't get 40' out of a # 6 nozzle with funny pipe and saddle tees, I do it all the time.
    Posted via Mobile Device
     
  3. DanaMac

    DanaMac LawnSite Fanatic
    Posts: 13,156

    Is this the chart you used? http://rainbird.com/documents/turf/chart_5000.pdf

    If so, look at the chart for 45 psi, and it will give you 46' with a 6 GPM nozzle. That is the pressure at the HEAD, not the at the P.O.C. when nothing is running.

    Most likely you will have about 30-40 psi at the head, if you start at 50 and have 2-3 heads per zone.
     
  4. turbosl2

    turbosl2 LawnSite Member
    Posts: 56

    Ok, i wasnt sure what to call it, i think funny pipe may be a TORO trade name. Swing pipe makes more sense. How should i go about doing this, i have never done this before. I am wondering if there is a crack or something in the main line. It could be me but i dont seem to be impressed with the rain curtain technology. I was even going to try to upgrade some heads to the Rain bird Falcon 6504 because they had 3 nozzles, distance, close and mid range.

    What i end up with is larger droplets at the end of the stream resulting in darker green hollow circles of greener grass. Then some minor green grass around the head, then anywhere in between doesnt get as much water. And today i measured the distance and say 25' from each 6GPM nozzle (for a total of 50' diameter. Now add sandy soil, 80-90 deg temps and i can see the heat stressed spots in the yard clear as day. And it starts 2' from the head, then 3' from the end. Everything else is green.

    I mention this because i would think it would work as should if the nozzle threw as intended. I think a 6GPM is like 47-49' at 50PSI, thats a large radius, something like that. I am getting about half
     
  5. turbosl2

    turbosl2 LawnSite Member
    Posts: 56

    Ahh, yes this is the chart i been using. If i am getting 25' i seem to have a real problem, its not even on the chart.
     
  6. turbosl2

    turbosl2 LawnSite Member
    Posts: 56

    What should i do? 25' with 2 6GPM nozzles running means i am below 25PSI on pressure at the head. Idk how it could be this low.
    How to you figure on paper the pressure at each head when changing the nozzles. Is there a formula or calculator you use. I just checked my pressure with my gauge, it is 55PSI. But its almost 11pm so i am sure the demand for water on the main is lower too
     
  7. DanaMac

    DanaMac LawnSite Fanatic
    Posts: 13,156

    As I mentioned, you will have to nozzle down to get anywhere close to your distance, but you will not get your 47'. It's not going to happen, Uh uh, no way. Just being honest and up front. It is a design issue on your end, and we all made them in the early days. You can either redesign and reinstall, or you can make due. Renozzle, get as much distance and as close to head-to-head coverage as possible, and don't rely on the rain curtain technology to get enough water down in front of the heads.
     
  8. turbosl2

    turbosl2 LawnSite Member
    Posts: 56

    I appreciate the honesty. Do you think if i were to change out the swing pipe to something else that is 3/4" and run 3/4" from the 1" line to the head it would do better, or do you think it will drop the pressure even more at the head. I was told using hte .5" swing would help keep the pressure up. I really do need the distance, i see for some reason the 3.0LA at 25PSI seems to throw more than i am getting now, and it only flows 3GPM but will lay down .51Inch of water using half the GPM, not sure how that is possible
     
  9. DanaMac

    DanaMac LawnSite Fanatic
    Posts: 13,156

    How are you figuring you are getting 25 psi at the heads with those nozzles? You have to take a field reading at the head to actually see what you are getting. It's going to take some time, and multiple nozzle change outs to get it right, or at least close. Are all the heads spaced at 47'? It's going to be a tough one. You might think about adding a head here or there, and moving some existing one, to get better spacing.

    Are you putting 6 GPM nozzles on every head? No matter the area it is covering? This is a no-no. Let's say for instance you have a 1 GPM in a 90 degree corner. Then you should have a 2 in a 180 degree, a 3 in a 270 degree, and a 4 in a 360 degree. Matched precipitation.
     
  10. DanaMac

    DanaMac LawnSite Fanatic
    Posts: 13,156

    I'm tagging out to someone else for the night, 5:00 AM start time at the trail head tomorrow.
     
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