job along roadway

Discussion in 'Irrigation' started by skrats, Jan 13, 2006.

  1. skrats

    skrats LawnSite Member
    Posts: 92

    Hello everyone

    i have an opportunity to take on a large irrigation project. There is a roadway that needs to get water on both sides of the road and it is 2500 feet long. My questions concerns the size pipe i will need to carry constant water the whole length. i hope that 4 inch sch 40 pvc will be sufficiant as a main line. Assume the zones will be 1 inch poly. There will be a 40-45 gpm provided. thanks for the help as this site is great assurance.
     
  2. PurpHaze

    PurpHaze LawnSite Fanatic
    Posts: 5,496

    Personally I think someone needs to rethink this. You're going to be provided only 40-45 GPM in a 4" line that normally carries 200+ GPM? And... at what PSI?
     
  3. dcondon

    dcondon LawnSite Silver Member
    Posts: 2,246


    I don't think you will see much PSI with those numbers.
     
  4. JCinTx

    JCinTx LawnSite Member
    from Texas
    Posts: 30

    Have you completed a design yet? You need to figure the hydraulics on it,…place your heads, zone it, and size your pipe for pressure and flow, don’t make any assumptions, it could cost you a lot of money.
    JC
     
  5. dcondon

    dcondon LawnSite Silver Member
    Posts: 2,246

    I forgot to ask, is it just flat ground????
     
  6. bicmudpuppy

    bicmudpuppy LawnSite Silver Member
    Posts: 2,781

    Like most posts like this, all you can really get in reply is a lot more questions. 1/2 mile of pipe x2 can you loop it? 40-45gpm means I figure 40gpm. How much are you watering? 1 mile of lateral spacing, but how deep? one row only? two rows? two rows would mean 2 miles of spaced rotors or around 200 heads on 50' spacing and if you can zone fulls and half circles sepeartely you could probably get by w/ 3gpm nozzles. Fulls would run for 2 hours for around 1/2" precip and halfs would run for 1 hour. Your looking at 16 zones with a total run time of around 24 hours. If you can loop it, you might be able to run 2" class pipe. Center fed 1" laterals are NOT going to get it done in this case. 1.5" laterals each way for the first two heads would be how I would lay it out. If you can't loop the main, then pipe size is going to depend on how you have to feed the main. If the farthest valve is almost a mile away your going to have to increase pipe size accordingly. If you can center feed the main so you only run 1/4 of a mile or a little over to the farthest valve, you may still be fine with a 2" mainline. If your static pressure is less than 60psi and you need an RPZ for backflow..............
     
  7. skrats

    skrats LawnSite Member
    Posts: 92

    This application is on flat ground. I was just told that i would have that constant supply (40-45) would psi be a better factor than gpm because i am not sure which he said. I do know that they have a line for me to get this from and the well its coming from is 15".
     
  8. skrats

    skrats LawnSite Member
    Posts: 92

    this is just one row of heads. They are intended to cover 15' from the roadway. It is not possible to center feed the main line. :( Also i thought i might have to decrease the pipe size toward the last valves that are farthest away.
     
  9. skrats

    skrats LawnSite Member
    Posts: 92

    I found a pressure loss calculator and entered the pipe size and length. There is really not a substantial amount of psi loss for the main line. I dont fully understand how to supply my zones with adequate water.
     
  10. JCinTx

    JCinTx LawnSite Member
    from Texas
    Posts: 30

    Skrats, GPM/PSI…you need both, gpm is your velocity and will determine your psi loss. To figure your psi loss, you need to know how many gpm’s your zone is pulling, start with your worst zone…the furthest one away usually or the one with the highest elevation, determine where you are placing heads, which from your post you stated 15’, all in a single row(nice and easy), 15’ sprays is what you need. Now you just need to figure how many you can put on each zone and still have the minimum head pressure, which should be about 30psi for a15’ spray. You stated you were supplied with 40-45 gpms, a ½ nozzle is about 2gpm’s and you’ll need 2 90degree nozzles @ about 1 gpm, so I figure that you could put ~22 sprays on each zone, but you need to go to your manufacturers catalog and see what nozzle you’re going to use and the gpm’s spec’ed for each arc, might get more out of it or less. What restrictions does your water source have,….are you hooking up to a meter or saddling in the 15” main?….Backflow device?….psi loss there also. You can pull 45gpm with a 2” sch 40, no problem, but the pressure loss will probably be too much at the distance you stated, using the 4” is equivalent to looping the 2” so that’s probably what you’ll have to go with. I wrote this quickly, it's about my dinner time, so I hope everything was somewhat clear….hope it helps a little!
    JC
     

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