simple question

Discussion in 'Irrigation' started by TPnTX, Jul 27, 2006.

  1. TPnTX

    TPnTX LawnSite Bronze Member
    Posts: 1,775

    Im studying irrigation in my spare time. I also have limited knowledge of past installs done by others. One in particular I'm using as my case study & I have a conflict.

    House has 55psi where the irr. mainline will ties in to the house mainline (1 1/4 Sch40 PVC).

    The irr mainline runs about 300 ft to the farthest zone. No hills. Calculating pressure loss I've determined that I need at least 1 1/4 irr mainline(SCH 40) for this distance.

    The install job they used 1" cl200 for the mainline.

    I just wanted to know what the general concensis is on this issue if you don't mind.
     
  2. Valveman

    Valveman LawnSite Member
    Posts: 53

    Bigger pipe, less GPM per zone, or booster pump.
     
  3. That question cannot be answered.

    The furthest zone...how many gpm?

    See what I mean....
     
  4. TPnTX

    TPnTX LawnSite Bronze Member
    Posts: 1,775

    I understand everything is relative to what is going to run at the farthest zone. The job consist of beds and lawn. So it's not one rotor. I'm looking for a resonable start point for the size of the irr. mainline. and what about cl200. Do we use that for mainline. What I'm reading tells me no but that my be just the "test answer" and not required by code.


    GPM is 23. I think I have yet to verify.
     
  5. TPnTX

    TPnTX LawnSite Bronze Member
    Posts: 1,775

    yeah I do understand that technically you can't answer a question unless you have the big picture in mind.
     
  6. TPnTX

    TPnTX LawnSite Bronze Member
    Posts: 1,775

    Maybe this is a better way of asking the question.

    PSI 55, GPM is 23 at the 1 1/4" House Mainline.

    Supply Location is at the front of the house.

    Phase 1 of the job
    Irrigate the front lawn and beds.
    Extend main line 300ft around the house for phase 2.

    Phase 2 is to irrgate back lawn and beds. The configurations is not known because there will be construction done which hasn't been designed yet. Pool spa patio etc.

    So for the optimum PSI determined by what we know is what I'm after.

    My figures say that 1" cl200 isn't optimum.

    23gpm @ 300ft

    1 1/4" sch 40 has a PSI loss of 8.9

    1" cl200 is 18.2 at 300ft.
     
  7. Dirty Water

    Dirty Water LawnSite Fanatic
    Posts: 6,794

    If you truely use 23 gpm with your zone, then use 1 1/4".

    Remember, you could have 900 gpm at your source, but you will only move as much as your spraying out the sprinklers.
     
  8. TPnTX

    TPnTX LawnSite Bronze Member
    Posts: 1,775

    I'm thinking more in terms of PSI/Pressure loss @ 300ft.
     
  9. jerryrwm

    jerryrwm LawnSite Bronze Member
    Posts: 1,274

    SDR-21 Cl 200 is fine for a mainline. You need to be careful when backfilling as in any buried pipe situation.

    At 23 GPM you would want to keep the velocity under 5-6 fps so 11/4" is the choice.

    If the mainline is already in and it is 1", then you would need to split the zones to around 12.0 GPM. Then the velocity would be in check and your pressure loss would also be managable.
     

Share This Page