How would you design this system

Discussion in 'Irrigation' started by Ground Master, Aug 14, 2002.

  1. Ground Master

    Ground Master LawnSite Senior Member
    Messages: 505

    Have a customer (my crew mows the yard) who recently had a sprinkler system installed. Although I install systems I had to pass on this one. I have yet to see it run but have questioned (to myself) the design of this system.

    1. About 34,000 sq. ft. of lawn area
    2. 1" service line and 1" meter in basement located 70 feet from street.
    3. 80 psi static pressure.

    What I've seen installed:
    1. 1" copper mainline (starts in basement to outside wall) to PVB then 1" PVC from outlet of PVB to mainline.
    2. Entire mainline is 1" PVC (furthest valve grouping is 130')
    3. 1" Poly for all lateral lines.

    What I think should have been installed:
    1. 1 1/4" mainline to a RPA (the pvb that is installed is not above the highest head on system)
    2. 1 1/4" copper from outlet side of RPA to the mailine in the ground. I hate seeing pvc exposed to the sun on the outlet side of vacuum breakers......looks bad, becomes brittle over time.
    3. 1 1/4" PVC mainline.......
    4. Should have installed 1 1/4" poly from electric valve to at least first head on each zone. Some lateral runs are 100' to 1st head!
    5. My general thoughts are that the installer/designer undersized the increasing the mainline just 1 size over service line makes a huge difference in pressure losses and velocity.......

  2. HBFOXJr

    HBFOXJr LawnSite Bronze Member
    Messages: 1,712

    Calculate the flow of the largest zone and the longest pipe run main and lateral to the 1st head and the flow of that zone. Now do all the pressure loss calculations.

    The flow may be completely appropriate for the pipe size and distance. It doesn't worry me. I'd be more concerned about head spacing, locations, nozzles sizes and designed precipitation rates.

    In other words, can the system provide the needed amount of water based on your historic evapotranspiration info and in a reasonable amount of time? And is the water supplied evenly and efficiently.

    Could be another classic example of the site being "covered" but not truly irrigated.

    Let us know.

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