Fairly big irrigation job help

Discussion in 'Irrigation' started by Huskerduck, Sep 19, 2013.

  1. Huskerduck

    Huskerduck LawnSite Member
    from OR
    Messages: 13

    Hello all!

    I'm having some strange results trying to put in a irrigation system and it has to do with pipe sizes. I have a 3" main coming into this area that is supposed to be around 100 gpm and basically about 80 P.S.I

    I have learned in the past not to trust manufactures flow charts on their nozzles so I always run a "test" manifold as to get max results but am finding weird results.

    Using Hunter i40 rotors I am finding that placing 8 rotors directly off 3" main with a 2" Tee I am @ 60 p.s.i and seem to have good steady flow without kicking the pump into a feedback shutdown. These rotors are all within a 20' length of pipe and bumping the rotors up to 10 drops pressure to 40 P.S.I and significantly drops the radius by 5'-8' so I'm going to call 8 good.

    Now the weird part, if I move my test manifold to another existing spot 180' down a 2" main and controlled through an 1-1/2" valve and 15' of 1-1/2" pipe my results barely change which goes against every flow chart out there but they are always based on 100' runs which really has me guessing how to properly size the pipe. Logic tells you to run a 3" valve into a 3" pipe to first 2 sprinklers, then 2-1/2" pipe to next 2, 2" next 2, 1-1/2" to the final 2 but when I experiment I find no difference. I am seeing I can run 2" through a 2" valve and cut the pipe down to 1-1/2" for half the run and probably 1" to the last sprinklers.

    Obviously Im trying to maximize cost efficiency in Valves and controllers since we have switched to DIG solar controllers instead of wires for obvious reasons ( mice voles gophers) at first I though GO BIG and spray a 60' radius but the zones needed added double the valves/controls/boxes but more so maintenance and trouble shooting

    How would you size your pipe on a 200' zone with 8 rotors and would you use a 2" valve?

  2. Wet_Boots

    Wet_Boots LawnSite Fanatic
    Messages: 50,752

    Not knowing what nozzles you are running, conjecture is all we got. In any event, valve size and pipe size don't have to match. Zone valves are often smaller than the pipes connected to them.
  3. Huskerduck

    Huskerduck LawnSite Member
    from OR
    Messages: 13

    I have tested every nozzle and am down to the smallest nozzle which is around 8 gpm, again, I would love to throw on golf course type sprinklers like Eagles or i90s but you add some serious GPM to get those to perform and the cost in increased pipe size and more valves and controllers doesn't seem to flush for maintenance down the road.

    So I am torn between the 8 gpm and 11 gpm nozzles.

    I was under the impression that 1-1/2" valves put a 30 psi drop due to velocity being @ 18.5 when around 100 gpm

    A 2" valve shows much better velocity @10.5 but all this is dependent on 100' runs, is that correct? I know you're after a velocity of 5 but this means 3" valves as well as pipe to the first nozzles and then dropping to 2-1/2" for next 2 etc. to keep those velocities down.

    Does the 100' flow charts divide equally by distance as in a 10' run is divided by 10 off the 100' flow charts?
  4. Huskerduck

    Huskerduck LawnSite Member
    from OR
    Messages: 13

    I had someone recommend i40s, I have been using Falcons and 8005s to date, in the picture those 3 "circles leading up to the new area are watered with 2 8005 on out sides and 1 falcon in the middle with 20 gpm nozzles and all three run well at the same time, they replaced 30 rotors that wasted about the same water because of the rounded corners and I'm doing testing to add to these since they are 3 independent valves so I can use 2 for this project and save the cost and maintenance but they are off a 2" main coming from 180' away from the 3" main.

    I would change this to 3" mains but I'm just not seeing all this velocity and friction loss charts are showing after the system is on. My guess is the charts are more for water hammer on valves and rotors?
  5. Wet_Boots

    Wet_Boots LawnSite Fanatic
    Messages: 50,752

    Are you kidding? Do you visit electrical forums and ask this about wire? :dizzy:

    Understand this about charts. Nozzle performance is one thing. Pressure losses through valves and pipe and fittings is another. Go ahead and be skeptical about nozzle charts in all things but the flow numbers.
  6. CAPT Stream Rotar

    CAPT Stream Rotar LawnSite Fanatic
    Messages: 6,201

    Man if you got 3" main use it for all you can...Bump your pipe down so you keep within your FPS.
    Have you thought about using valve in head?

    On the few installs I've done with big water My old boss was big on a 2 Inch feed brought to a 1.5 reducing T on each side with poly. Push that big water as far as you can.. Keep your friction loss in mind, take some pics!

    Some supply houses will draw you up a plan for free if you buy from them.

    Good luck

    :) ed
  7. Huskerduck

    Huskerduck LawnSite Member
    from OR
    Messages: 13

    I guess if electricity and water flowed the same, I probably would and no I'm not kidding probably because electricity doesn't have hydraulic hammer or velocity ratios that may or may not compound on themselves when using a $6k VSD and we haven't even discussed the difference between spring time pond water and end of season pond water with completely different viscosity

    My question was are the charts equally divisible/multiplied since every chart available is figured on charts of 100' runs, does velocity compound upon itself the further the run as in.......is a valve a fitting or a 6" length of pipe or both. Is a 20' length of pipe 20% of a 100' run or is a mile long pipe 5000% of the charts because we actually run a 1.5 mile 2" pipe under pressure and I guarantee is follows none of these charts for the last decade. But thanks for your "help" I was just baffled why my manually operated manifold tests weren't following flow charts and figured I may try and save a thousand dollars on pipe

  8. Huskerduck

    Huskerduck LawnSite Member
    from OR
    Messages: 13

    I would love to use valve in head but in all honesty on a project this size theres really only one head that makes sense when weighing in price on valves/controls and unfortunately I let a supply house recommend a Hunter i40 without looking at its performance charts and got scammed on 10 of them for a test manifold. I was actually told the i40 outperformed a Rainbird Falcon and it's the other way around in spades at 1/2 the price so I am a little leery on advice from people trying to move inferior products or get rid of higher priced goods like 3" pipe. We've been down this road before to the tune of 45 zones/1200 heads that a "pro" installed and couldn't keep 5 acres green until I halved the zones and have hundred of spare heads now. I was just interested in why a test I performed showed an unexpected result and it came down to our VSD
  9. Stillwater

    Stillwater LawnSite Platinum Member
    Messages: 4,889

    So what's your question.?
    Posted via Mobile Device
  10. grassman177

    grassman177 LawnSite Fanatic
    Messages: 9,795

    I can appreciate the dedication to install and design correctly, but I too find that the charts lie sometimes, they are made imo being cautious. however, fps still holds true.........but use all the gpm you can, and pressure

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