Pump-fed irrigation system

Discussion in 'Professional Discussions' started by MontanaIrrigation, Jun 7, 2019.

  1. MontanaIrrigation

    MontanaIrrigation LawnSite Member
    Messages: 1

    A client has water rights to a lake approximately 1800 feet from where the desired intake is for the irrigation system. He desires to run a 6" pipe from the lake to the intake of the irrigation system. He's planning on irrigating between 2-5 acres of lawn and native vegetation.

    The lake location has a pump currently and has power to the pump. The only concern that I have is that the irrigation system will need to command the pump on and off. Has anyone tried commanding a pump that is nearly 1/2 mile away from the irrigation system? What are the concerns of doing so. I suppose a long wire can be run but it seems like a long ways.
     
  2. BrandonV

    BrandonV LawnSite Fanatic
    Messages: 5,024

    Well you’re going to have to run a pipe there regardless. Where is the power for the pump coming from. Use a pressure tank and maybe keep the mainline charged all the time?
     
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  3. BrandonV

    BrandonV LawnSite Fanatic
    Messages: 5,024

    6” btw seems overkill maybe 3”
     
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  4. Joetee

    Joetee LawnSite Member
    Messages: 71

    The system needs to be setup so that the pump run non stop as much as possible. Your water supply gpm needs to match as closely as possible to the gpm used at the sprinklers.
    If not, if the pump cycles on and off often, it will burn up the pump fairly fast.
    If the sprinklers are not installed yet, the gpm in each zone should be very close to the gpm supply.
    Also the faster the water velocity flows in the pipe, water pressure will decrease for each zone depending on how far the pipe runs. So pipe size is critical. A little big is ok but to small and you will have trouble with pressure at each sprinkler.
     
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  5. stebs

    stebs LawnSite Senior Member
    Messages: 577

    I’m about 900ft on my system. There’s a relay at the controller that changes the 24v signal from the controller to 110v which runs down to the pump. There’s another relay at the pump that takes the 110 and controls the pump controls.

    What kind of elevation change if any are you looking at between the lake and irrigation?
     
  6. sjwater

    sjwater LawnSite Member
    Messages: 31

    So, the controller needs to fire up the pump and shut it down when irrigation is done. My guess is Master Valve of the controller should be able to do this.

    I am not sure what the voltage and current rating of the pump is. But, lets say it is a 230V/115V standard pump with say 15Amp rating. Then there are basic pump start relays out there that can be used to activate the pump by the controller if neede.

    I guess the Master Valve wire form the controller connects to the pump start relay (it is a 24V signal) and everything would work. I used this site to calculate the wire size for 1800 ft run:
    http://www.paigewire.com/pumpWireCalc.aspx?AspxAutoDetectCookieSupport=1

    Lets say 12AWG wire is used at roughly 50 cents per foot (for 2 wires) and needs to be buried or conduit (I am not sure about the price of wire). That is roughly $900 for wires and a generic pump start relay (say for $50) and that would do the work, again assuming the pump is rated at 230V/115V.

    Another way to go is use a wireless pump relay (WR-110) from www.aivaka.com which does the same thing except no need to deal with the wiring the pump start relay to the controller.
     
  7. enorl76

    enorl76 LawnSite Senior Member
    Male, from Orlando, FL
    Messages: 305

    Don’t do that. Don’t run wire a half a mile.

    Just use a pressure switch, a cycle stop valve, and a small 4 gal pressure tank at the pump side.

    This does several things:
    - don’t need to spend money on wire that far
    - valves opening, will determine if pump comes on
    - prevents dead heading if a valve doesn’t open, a downfall of pump relay type systems

    I think I saw a design of about 25 gpm per zone, so using at least 2" pipe would be minimum. However I'd go with at least 3", given the distance of 1800 ft.

    However, you said 2-3 acres... at 25 gpm per zone that’s a lot of zones and a long run time. Consider upping the pump to a 3HP sta rite DHH and zones to be about 50-70 GPM each with a minimum 3” mainline running that far. Again, using a pressure switch set at 55 psi cutoff.

    This assumes not too much elevation change between the two different sites though. Given the distance, you might need to run the pipe first, cap up the pump side end with a pressure switch. Close the output end and fill up the pipe, letting air out of the pump end, to see if there’s a standing pressure which would indicate elevation change.

    If there’s more than 10 psi, a different pump is needed, probably a 2 stage or 3 stage to get you the desired pressure at the end with desired flow. A lot of choices on that.

    Of note, my dad's property off a lake has a 700 ft mainline thats 3" PVC, and the elevation change there creates a 5 PSI static pressure at the pump, which is a Sta-rite DHH 3HP. We run about 50-60 GPM per zone, some zones all Maxipaw rotors @ 3.5GPM each, and some zones the larger golf course rotors.

    My dad's system does run off a relay, which I regret, because a couple of times a solenoid didnt open and the pump deadheaded. So I had to replace all the piping around the pump due to overheating. One way to prevent that is to have a small water hose valve cracked open just a little to keep water moving if the pump is on. Problem with that is that that valve always stays open so the whole mainline drains out when the pump goes off... Next time that incident happens, I will replace the control system with a pressure switch, cycle stop valve, and small pressure tank as I mentioned above.

    Lot of variables here, and gist of my post is don’t bother running a signal wire all the way. Just use a pressure switch and basically keep the mainline pressured all the time.
     
    Last edited: Jun 11, 2019
  8. enorl76

    enorl76 LawnSite Senior Member
    Male, from Orlando, FL
    Messages: 305

    Another consideration is if the pump can flow >50 GPM, keep the zones at 25 GPM, and use a clock like the Rain Bird LXME that can run multiple valves at the same time. I can find these all day on ebay for $100. This would shorten the overall runtime of the system.

    When running the LXME in flo-manager mode, you can plug in the GPM available (ie the pump's maximum capable value) as 80 GPM, and each zone's GPM at 25 GPM, and that timer will automatically run as many valves as it can, up to 2 per module, and a total of 4 or 5 simultaneously. (And you dont have to have a flow sensor, btw. You can plug these valves in manually.)
     
  9. ArTurf

    ArTurf LawnSite Fanatic
    Male, from Ark
    Messages: 6,036

    A
    A simple safeguard against deadheading is a pop off valve
     
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