Pumping Out of Shallow Irrigation Canal Advice

Discussion in 'Irrigation / Sprinkler Forum' started by 71Ranger, Mar 3, 2008.

  1. 71Ranger

    71Ranger New Member

    Messages:
    3
    Hi All:

    I've finally been given a permit to pump out of an irrigation canal adjacent to my property and have a couple questions.

    The spot where I'm allowed to put the pump is in a curve of the canal, so the water moves a little faster there. Additionally the canal is only about 1 foot deep. The guy who approved the permit said he would allow me to put a sump in the canal and he recommened I use a 12" diameter pipe for the sump and said to put it deep enough "to get adequate submergence over your suction".

    Does anyone know how deep I would need to go below the bottom of the canal to make this work? Also, how far above the bottom of the canal should the top of the pipe be?

    By the way, I'm only allowed to pump out 45GPM and the pump I've been approved to use is the Goulds GT-20. I plan to use a 1" pipe in submerged in the sump and the pump will be within 75 feet of the canal. The land is very level.

    Thanks for any advice anyone may have.
  2. Wet_Boots

    Wet_Boots Sprinkler Guy

    Messages:
    798
    Location:
    Metro NYC
    Free water is worth the effort to get, but you won't be pumping clean water, and it won't be at pressures high enough for some sprinkler heads. How large an area do you want to cover?

    By the way, even without the 75 foot distance between pump and water, you couldn't use a one inch suction pipe. Figure two inch pipe. What elevation difference between pump and canal level? (this figures into the suction lift, which should be kept to a minimum)
    Last edited: Mar 4, 2008
  3. 71Ranger

    71Ranger New Member

    Messages:
    3
    Thanks for the reply and advice. I'm trying to irrigate about 1.5 acres of grass. The pump will be essentially level with the level of the canal and I can be flexible as to how close the pump is to the canal (I can get it within 25 feet if I have to).

    Any idea on the depth of the sump question? Never having done anything like this I'm unsure of what's necessary so the pump doesn't end up sucking air.

    Thanks!
  4. Wet_Boots

    Wet_Boots Sprinkler Guy

    Messages:
    798
    Location:
    Metro NYC
    Maybe three feet or so. Some guys will use a well point in the sump for filtering the suction.
  5. Bob NH

    Bob NH In the Trades

    Messages:
    3,317
    Location:
    New Hampshire
    I would use a large pipe or tile stacked up with a screen around and over the top to prevent anything from getting sucked into the sump. Use the largest you are permitted to use and let the screen rise above the maximum level of the water and to within maybe 3" of the bottom.

    A vertical section of inlet screen in the water is very desirable because a height of only 1/4 of the diameter has as much inlet area as the area of the pipe. For example, 3" height of screen around a 12" pipe has the same area as the 12" pipe. A do-it-yourself screen can be made with heavy hardware cloth covered with a finer metal screen. If you can get bronze screen it will last longer but you might be able to get some heavy duty nylon screen.

    You should try to bring the pipe from the sump to the pump with a slight rise so there is no place that a bubble can collect in the suction pipe.

    You will need a foot valve at the inlet end.

    Closer to the source is a great advantage.
  6. PEW

    PEW DIY Senior Member

    Messages:
    487
    I am using the predecessor to the GT-20 which has a 2 inch suction and runs on 110v at the end of 375 feet of # 8 wire, pumping from a river. I have no problem feeding 10 maxi-paws per zone. All pressure lines are 1.5 inch, on the suction side I have about a 3 to 5 foot of lift, on the pressure side there is about 12 feet of lift, and the longest run is about 500 feet from the pump.

    Also worth noting, it has been going strong for about 14 years without any problems, including being completely under water at least 4 times.
    Last edited: Mar 7, 2008
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