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Educate me!

Discussion in 'Irrigation' started by Dirt Boy, Jul 1, 2008.

  1. Dirt Boy

    Dirt Boy LawnSite Senior Member
    Messages: 489

    Looked at a job recently, and am wondering if I'm thinking right, or else please enlighten my feeble brain.
    Large home sitting pretty much on a hill, 2 3hp wells which can either be in the same loop or separate. One is primarily for the house, and one is primarily for the machine shed. But he also uses them to fill a pond. Each pump is rated at 32.6gpm at 50 psi or 30gpm at 70 psi according to the guy that put the wells in.
    There is a 1 1/4" line running around all this which is aprox. 500'

    My question is this: is this a screwy setup?

    My thoughts: It seems to me that the line is undersized and the owner is not really getting the benefit of the well capacity. A 1 1/4" line is rated at something like 22 gpm and then the pressure losses over that amount of distance is going to have some affect.
    If you have a million gallon capacity supply and a 1 1/4" line, you are only going to get so much out the end of the pipe.
    If the pump outlet is 1 1/4" shouldn't't you attach it to a larger pipe to run to wherever? If the pump is putting out 30gpm, your velocity is going to be out of bounds if you are attempting to use the capacity of the pump. I realize that if there is no call for the volume, nothing is wrong.

    Hope all this rambling makes sense:dizzy:
  2. GreatOutdoorsContracting

    GreatOutdoorsContracting LawnSite Member
    from MO
    Messages: 21

    you say 1 1/4 line but of what material ie: class pvc, copper, pex, schedule 40 all have different friction loss, flow rates, velocity etc.
  3. Dirt Boy

    Dirt Boy LawnSite Senior Member
    Messages: 489

    Not certain what all of it is, but from the well to the house and then from the other well to the machine shed is the blue pex type line.
    Also the pumps are of the VFD type.
  4. Rockz

    Rockz LawnSite Member
    Messages: 25

    If the 1 1/4" line is in a loop, I think it would be good to 44 GPM?
  5. Waterit

    Waterit LawnSite Silver Member
    Messages: 2,931

    If it's 1-1/4" PVC, it's undersized UNLESS it's a loop. 1-1/4" thinwall is good up to 28GPM, sch. 40 up to 22. So if it's not looped, should be 1-1/2" thinwall or 2" sch. 40.

    And you're right - you can't get 10 lbs. out of a 5-lb. bag, especially when sizing pipe.
  6. Dirt Boy

    Dirt Boy LawnSite Senior Member
    Messages: 489

    Basically it is a loop, they have the option to cut one out of the loop.

    I just don't see how an 1 1/4" line, regardless of what type it is, is going to:
    1. allow 60 gpm usage
    2. be on the charts for safe velocity

    Which leads me to ask: How does it work for a 30 gpm pump to have an 1 1/4 outlet?
    And likewise other plumbing items, PVB's, valves, etc. are rated for far higher flow than their pipe size inlet/outlet.
    Is it the build of these items?

    Thanks, I ain't got no book learnin, so, I'm relying on you pro's
  7. Waterit

    Waterit LawnSite Silver Member
    Messages: 2,931

    1-1/4 won't allow for 60GPM, but would work if only 1 pump was running at any given time. Looping allows you to go down one pipe size, since pressure/velocity should be same throughout in the loop. 2" will work for 60GPM if looped, but 2-1/2 would be better.

    Yes, it is the build, years of engineering R&D.

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