Tuning new system - PR questions

Discussion in 'Irrigation' started by goodmatt78, May 23, 2013.

  1. goodmatt78

    goodmatt78 LawnSite Member
    from ohio
    Messages: 18

    I just installed a system using PGP rotors and red nozzles. I have static of 45 psi and 12 GPM (on interior 1/2" line hose bib)...exterior main line is 1" and we are tapped in a within 1 foot of that entering the house with 1" to supply the system.

    I balanced the system and plan to do an audit this weekend to better determine the watering duration.

    Currently I use the following nozzles:

    90deg - #2
    180deg - #4
    270deg - #5-6
    360deg - #7

    Irrigation tutorial suggests: #3,#6,#8,#9

    I am almost exactly 75% of the GPM recommended on irrigation tutorials.

    Currently running 25min/zone w/ 6 zones and 4 heads per zone. My most exhausting zone is at 8.4 GPM now (charted for 40psi).

    I plan to renozzle a zone this weekend to see if I can bump up nozzles without ill effects from pressure drop.

    Currently I show about 40 psi on a hose bib while running the system. I figure I am probably already below 35psi at the heads. Sound about right? Therefore, I am not sure if I can up my nozzles more.

    What PR should I be aiming for. Around .5 in/hr?

  2. Kiril

    Kiril LawnSite Fanatic
    Messages: 18,335

    There is no PR to aim for. Zones should have been designed per available flow and area to be irrigated, with a little overhead for flow and pressure fluctuations. While you can play with different nozzles a bit after install using the adjustment screw, that would only be to fix poor design. The rest of it (ex. PR) comes into factor when scheduling the controller.

    Also, don't know what you mean by "75% of the GPM recommended on irrigation tutorials". Assuming all the radii and nozzle pressures are the same, the design GPM per nozzle should be an exact multiple of the output for your 180 degree arc on the other non-180 arcs, with a few exceptions. You will probably never achieve this exactly with PGP reds, but you need to get as close as you can with the nozzles provided without having to use the adjustment screw excessively.
  3. Mike Leary

    Mike Leary LawnSite Fanatic
    Messages: 23,172

    Ditto what you said. I've seen PGPs dogged-down so far that they only threw 5'! :hammerhead:
  4. goodmatt78

    goodmatt78 LawnSite Member
    from ohio
    Messages: 18

    75% meant that it is suggested to use 3,6 and 9 nozzles (since you have wind issues with the smaller nozzles) and I am using 2,4 and 7. Yes I am matched but using smaller nozzles than suggested.

    I did a quick audit last night and I am putting down about .3"/hr and keep 40psi at an open hose bib while running. I will try nozzling up to 3,6,9 and see how it does. I think my heaviest zone will still around 11GPM.

    I would like to get high enough PR to only water 4 times a week.

    As for the diffuser, screw I have them set to just nick the stream, but not shorten the radius.

    Thanks for the replies.

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