How do you compute precipitation rates?

Discussion in 'Irrigation' started by zimmatic, Apr 10, 2008.

  1. zimmatic

    zimmatic LawnSite Senior Member
    Posts: 411

    When you install a system and make sure the correct nozzles are in all the heads, how do you compute the precipitation rate for a zone?

    Using the flow/performance/precipitation charts for the nozzles one may be using, do you take the nozzles within each zone find there precipitation rates, add up all the rates then divide it by the # of heads within that zone?

    The reason for my question is to make sure/confirm the method, since I am installing many Irritrol smart dials and it ask for the zonesÂ’ precipitation rate. I work my arss properly installing the systems and take the time to program these controllers, I hate to have to reprogram them all.

    All help is appreciated good or bad.
     
  2. CAPT Stream Rotar

    CAPT Stream Rotar LawnSite Fanatic
    Posts: 5,961

    how about google?
     
  3. You are in a prickly mood these days Eddie. Did a goose bite your arse?
     
  4. Tom Tom

    Tom Tom LawnSite Bronze Member
    Posts: 1,278


    Precip = 96.3 x (gpm of area)/Square feet of area

    You could also compute the precip rate by figuring how much water goes thru the water meter(gpm) for each zone you have(area).

    I have the smart dial at my house and used 1.4"/hour for spray zone and .6 to .7/hour for rotor zone.

    If you don't compute some of the zones precip rates, it will take some trial and error, ie. adjusting the rate on the controller to get it dialed in.
     
  5. Wet_Boots

    Wet_Boots LawnSite Fanatic
    Posts: 48,017

    Now, for extra credit, show us how the 96.3 factor is derived....
     
  6. DanaMac

    DanaMac LawnSite Fanatic
    Posts: 13,156

  7. Tom Tom

    Tom Tom LawnSite Bronze Member
    Posts: 1,278


    (60/7.48)/12
     
  8. Wet_Boots

    Wet_Boots LawnSite Fanatic
    Posts: 48,017

    No fair copying off the web. I want to see complete units analysis, and show all your work.
     
  9. DanaMac

    DanaMac LawnSite Fanatic
    Posts: 13,156

    Only gone thru the class once, didn't take the test, and haven't used in real world practices yet. Just posting a link for the guy.
     
  10. Tom Tom

    Tom Tom LawnSite Bronze Member
    Posts: 1,278

    Post 200!

    If you ever get out to Colorado, Dana, Tony, and I will scribble it out on a napkin for you over a round of :drinkup:
     

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