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Flow from 1" copper............

Discussion in 'Irrigation' started by mjstef, Aug 28, 2013.

  1. mjstef

    mjstef LawnSite Member
    Posts: 146

    Got a really good customer of mine that wants 1.25 acres under irrigation and it's been many years since i have done a system this large. We are trying to get away with the least zones possible due to the rocky nature of the soil on the property. I am trying to remember what a 1" copper pipe will flow at 40 PSI. The well pump is 1.5HP 20-25 Gal per minute, 290' deep with static level of 240' per the installer. I would imagine the 20-25 GPM is with the 1 1/2 main line wide open and no pressure. Cannot find consistency between flow charts i find online! 1 says 38 GPM and another says 13.5 GPM for a 1" line at 40 PSI! Any help would be appreciated. Normally i would sub a job like this out but all companies here are at least 3-4 weeks out and we need to get sod down as winter is on it's way!!! Thanks!
  2. Mike Leary

    Mike Leary LawnSite Fanatic
    Posts: 21,975

    If it's 1" Type "K" copper, you'll get 12 gpm if you follow the five feet a second rule. Bear in mind, per 100', you'll lose close to 6 psi in friction loss.
  3. DanaMac

    DanaMac LawnSite Fanatic
    Posts: 13,156

    Flathead Valley, MT? I was just there in Bigfork two weeks ago. My brother lives there. Beautiful area, love it.
  4. Mike Leary

    Mike Leary LawnSite Fanatic
    Posts: 21,975

    Seems strange that copper is used out there, is there a reason to not use poly?
  5. irritation

    irritation LawnSite Gold Member
    Posts: 3,248

    I doubt it was used from pump to house, in fact a 1.5 hp pump should have at least 1-1/4" piped to the pressure tank.
  6. Cape Atlantic Landscaping

    Cape Atlantic Landscaping LawnSite Member
    Posts: 37

    1.5 inch Sch. 40 would carry that 20-25 GPM a lot nicer than the 1 inch copper and only has a friction loss of 1.75 PSI per 100ft.
    When designing with a pump if the well installer tells you 20 or 25 GPM I would stay with the lower number and then do a 10% rule and then design at 18 GPM
    What is the static pressure at the POC?
  7. Wet_Boots

    Wet_Boots LawnSite Fanatic
    Posts: 47,665

    How is one-inch copper of any sort, a part of the irrigation picture here?
  8. greenmonster304

    greenmonster304 LawnSite Gold Member
    Posts: 3,097

    It's probably the feed to the house after the pressure tank which is where he is thinking of tapping.

    He could dig up and tap right by the pitless. This way he could eliminate the house plumbing completely.
  9. mjstef

    mjstef LawnSite Member
    Posts: 146

    Correct. Feeding from the pressure tank in the basement. Will pick up 1" poly right outside the house. Same way my house is plumbed and i have 18 zones. Not even going to try and dig at the well line as it had to be blasted in. With the yard hydrant wide open the well holds just under 45 psi................
    Last edited: Aug 28, 2013
  10. 1idejim

    1idejim LawnSite Fanatic
    Posts: 9,433

    I am with GM, close as possible to the well head.

    Static means little.

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