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Design thoughts

Discussion in 'Zone Talk' started by David Vance, Jan 2, 2020.

  1. David Vance

    David Vance LawnSite Member
    from Texas
    Messages: 3

    I am planning to add a sprinkler system to my wife’s horse arena. I am going to have an 1100 gallon tank for storage. I will be Using an AMT 7.5 hp pump (4803-95) which will pump to 4 rotors(1 rotor on each zone). I want to use Toro TS90 rotors, I believe I can put one on each side of the arena and get adequate coverage at 70psi. I was planning to run 1.5” pvc buried around the edge of the arena, which should give me a little pressure increase and still have enough GPM for the big rotors. The arena is 200x140. I was going to use toro p220 valves to regulate pressure to the rotors. The rise from the pump to the highest rotor is about 18”. Is it better to place the valves closer to the pump or can I get away with placing the valves close to the rotors. If the valves are closer to the pump I have to run more PVC. If they are closer to the rotors I can run less pvc and just have to run more wire. Appreciate any input, I want to do this once and avoid a lot of trial and error.
     
  2. Hayduke

    Hayduke LawnSite Senior Member
    from Oregon
    Messages: 295

    Not sure about the answer to the original question. But I am curious as to how quickly the storage tank refills? How many zones are you thinking and how much water do you need to put down? Lets say the the 4 rotors are putting out a conservative 35 GPM each, so a total of 140 GPM. That means you could run the whole system about 8 minutes before the tank is dry. 1100 gallons spread out over a 200' x 140' area (28,000 square feet) is only .06 inches of precipitation, or about 1/16th inch. Is that enough to accomplish your irrigation goals?
     
  3. OP
    OP
    David Vance

    David Vance LawnSite Member
    from Texas
    Messages: 3

    This is for dust control, not for a complete soak. The 1100 tank refills from a 10k gallon rain water tank gravity fed at about 30 gallon/min. It also has a 3/4” line from a well. I want to run 1 rotor at a time 180 degree (about 2.5 min per toro) at 33-35gpm (per spec sheet) would be about 90gallons per rotor per 180 degree rotation. I figured I could reasonable run each rotor 5 min and get away with about 720 gallons.
     
    Crazy 4 grass likes this.
  4. Hayduke

    Hayduke LawnSite Senior Member
    from Oregon
    Messages: 295

    Thats a big pump just to run one at a time. The curve shows its output around 85psi/80gpm so it should do two rotors at a time, but I guess you are being wise to stay a little below the max capacity as you are doing splitting it into 4 zones. As for the original question, what's the cost difference between having the valves farther (more wire) or closer (more pipe), because it really doesn't matter one way or the other. And when you say the 1.5 " pipe will increase the pressure, that's not quite right. It may decrease the friction loss compared to what else you might use, but you pretty much have to use at least 1.5 inch pipe anyway for 35 GPM to avoid velocities that are too high. You might get away with 1 1/4" if you use Class 200 pipe, but then your velocities are still above recommended limits for 35 GPM.
    Plus, at 5 minute run time per rotor for a total of 720 gallons, you're down to .04 inches of water. Is that really going to be enough for dust control?
     
  5. OP
    OP
    David Vance

    David Vance LawnSite Member
    from Texas
    Messages: 3

    Thanks for your replies. I really do appreciate the input. As far as whether 0.04” is enough, I guess that will have to be a trial and error. Which I am ok with. I just don’t want to design/build too small of a system and have to go back to the drawing board. I did pick a pump to make sure I had enough PSI/gpm to run those rotors. Running 1 rotor at 35 gpm will allow my tank to refill fast enough as long as it rains.....
     
  6. Outlawn

    Outlawn LawnSite Bronze Member
    Messages: 1,257

    Shout at me if you need any help with it, Dave. I still have the same number.

    Stephen
     

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