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how far can i run 3/4 inch pipe?

Discussion in 'Irrigation' started by instyle, May 21, 2007.

  1. instyle

    instyle LawnSite Senior Member
    from Canada
    Posts: 380

    I will be installing a drip irrigation system, I have 300 bushes to water, if i am using .6 gph emitters, that is 3 gph(ish). how long of a 3/4" line can i run?
  2. CAPT Stream Rotar

    CAPT Stream Rotar LawnSite Fanatic
    Posts: 5,911

    i was asking the same question about 1 inch poly
  3. Flow Control

    Flow Control LawnSite Bronze Member
    Posts: 1,267

  4. CAPT Stream Rotar

    CAPT Stream Rotar LawnSite Fanatic
    Posts: 5,911

    who/drip maker or poly maker?
  5. Remote Pigtails

    Remote Pigtails LawnSite Senior Member
    Posts: 581

    Rotar I know fisher covered this. Every company who makes a piping product has specs. If a 3/4" poly runs for 10,000' it will allow for fewer gpm than one that runs for 10'. One practice service people lose is that since we rarely design we quit checking spec sheets.
  6. PurpHaze

    PurpHaze LawnSite Fanatic
    Posts: 5,496

  7. PurpHaze

    PurpHaze LawnSite Fanatic
    Posts: 5,496

    Length of run and GPM you'll be allowed to carry effectively depends on many variables; type of PVC pipe, starting PSI, total GPM used along the way, etc.
  8. WaterGuru

    WaterGuru LawnSite Member
    from Florida
    Posts: 39

    You will need 3 gpm if you figure 300 emitters at .6 gph. If you figure the planting is normal 2 feet apart, thats going to make the length you need to cover approximately 600 feet. 600 feet of 3/4 pvc will have a friction loss of 2.76 gpm. Depending on the distance from you point of connection and how much pressure and how many gpm you start out with. Add another .46 gpm loss per 100 feet. You will need 3 gpm for your emitters, plus another 3 (rounded up) for loss totaling 6 gpm. Then add the loss you will have from you point of connection to the first plant. Just for craps and giggles lets say its another 100 feet. So you will need to add another .46 gpm of loss to that, for a total of 6.50 gpm of water needed. If you do not have that to start out with your screwed.
    Naturally all these numbers were pulled out of my *** actual number will differ. But hopefully you get the idea of how to figure it out
  9. bicmudpuppy

    bicmudpuppy LawnSite Silver Member
    Posts: 2,781

    OK, we've seen this kind of crap before and I've just got to KNOW. Where do these people get GPM loss from a friction chart??? You lose PRESSURE, not flow. You lose PRESSURE from the friction of the FLOW. If you lost FLOW, you would not be losing anything to friction, you would be gaining because the flow was reduced. No, its not ROCKET science, but it is SCIENCE. The info is there for anyone to read. It isn't that hard to understand with some base knowledge (my 13 year old has a fair grasp now, but he's been lugging pipe with me since he was three). If I needed 3 gpm of FLOW, and I was running drip irrigation, I would not sweat the charts for 3/4" pipe unless I the run was a lot longer than 600'. Now, if I needed more than 30psi, I might get worried, but since we should all know that 1/2" pipe is more than adequate for most runs of 5gpm or less, then figuring the piping at 3/4" already has plenty of room built in for pressure loss. If we were running ONE pgp @ 3gpm at the end of a 600' run of 3/4. I might be inclined to get a chart out and make sure I wasn't losing enough PRESSURE to make a difference, BUT I am still reasonably sure w/o getting out said chart the PRESSURE loss of 3/4" classs or sch pipe is less than 3psi/100' and I don't see that being a problem for a 3gpm system.
    We are using pressure compensating emmiters? They are rated to emmit that .6gpm over a range of 20+psi? Sounds like we are good to go.
  10. What he said....(Bryan)

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