Pushing lake water 500' through 1" sch 40- Uggh

Discussion in 'Irrigation / Sprinkler Forum' started by Daltex, Jul 1, 2013.

  1. Daltex

    Daltex New Member

    Messages:
    15
    Location:
    Texas
    I bought a lake house with 2 acres to irrigate. The existing system uses a 3hp pump connected directly to a manifold with 8 zones feed off of it. The problem is that the pressure at the heads of most of the zones is closer to 20 psi. The runs vary in lenght up to 500'. All pvc is 1" sch 40.

    I know that even using 1-1/2" pipe would probably work for whatever reason they put in 1".

    Question: Considering that there is seperate runs for each zone, would it be feasible to tie multiple zones together along with decreasing nozzle size and get the pressure up to 30-35 psi?

    I tapped it at the manifold behind all the valves and the pump is putting out 43 lbs. there so would two 1" runs of up to 500' at a much lower velocity due to the lower orifice nozzels get the pressure up there?

    I plan on running a 2" line to the middle of the run and using that for the valves with 1-1/2" pipe at a later time but due to construction I won't be able to do this for another year or so.

    Thanks !!
  2. Daltex

    Daltex New Member

    Messages:
    15
    Location:
    Texas
    After reading more about my situation on other forums I think I will leave it as is until I can upsize the main feed line to a 2" line.

    If I reduce the nozzle size but add an additional zone with it's seperate 1" line it seems the pressure would rise but not significantly. The main concern I have learned is that by reducing the nozzle size I would experence a significant amount of wind drift to the water stream from the rotors. The area is windy most of the time and I need to stay with larger nozzle sizing to reduce the effects of the wind.

    I'll just wait until the time I can increase the supply line and then redesign the rotors (number per zone and nozzle size) to fit the pump performance curve. A few of the zones have not only long runs but a significant elevation rise.
  3. Terry

    Terry Administrator Staff Member

    Messages:
    15,418
    Location:
    Bothell, Washington
    It should have been 1-1/2" pipe for that distance.
    http://terrylove.com/watersize.htm

    My parents home had something similar for the irrigation, theirs was 3/4" and wouldn't do one zone.
    We ditched in new 1.5" and the problem was solved.
  4. DonL

    DonL Jack of all trades Master of one

    Messages:
    4,516
    Location:
    Houston, TX
    The key is balance, when you have different lengths and different heads, then you will have different flow.

    Flow control is key.

    It sounds like You need to up the pressure. You may have to many Outputs running at once, If so bigger pipe won't help, if there is no pressure on the input.


    Have Fun.
    Last edited: Jul 3, 2013
  5. Daltex

    Daltex New Member

    Messages:
    15
    Location:
    Texas
    I agree that an increase in pressure is the key. The problem is how to increase pressure when the friction loss of the 1" pipe is so large for the 500' run. I'm sure that if I dropped the flow to a few g/m that the pressure would increase but I think that the pump would be much more efficent if there was minimal friction loss. There is no elevation increase on the furthest zone and through the 1" pipe the flow drops alot. Increasing it to 1-1/2" or 2" would be a dramatic decrease in friction loss thus increasing the flow rate. The increase in flow rate will decrease the run time thus saving $$ on electric expense.
  6. DonL

    DonL Jack of all trades Master of one

    Messages:
    4,516
    Location:
    Houston, TX


    Very True, IF you have plenty of pressure at the pump outlet.
  7. Murphy625

    Murphy625 Member

    Messages:
    155
    Location:
    Michigan
    You could just install a second pump in series with the first.... The first pump would push its discharge into the second pump which would discharge into the 1 inch line. The pressure would build in the first, then build even more in the second.. You'd probably double the PSI instantly.
    I never said it was energy efficient, but you're limited to overcoming friction losses.
  8. Wet_Boots

    Wet_Boots Sprinkler Guy

    Messages:
    798
    Location:
    Metro NYC
    Some key information is what are the distances between the source and the various zone valves. The upstream side of the zone valves is where you want to be generous with pipe sizing, especially if there are any long runs. This relates to water hammer in the zone valves.
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