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Help with my sprayer

Discussion in 'Pesticide & Herbicide Application' started by sandy creek, Dec 15, 2010.

  1. sandy creek

    sandy creek LawnSite Member
    Messages: 96

    just got a lesco skid sprayer and spent a little time this evening learning how to work it. Going to calibrate it tomorrow but put a 4 gpm nozzle on it and adjusted the pressure till I got it to go shoot 4 gpm, then put on a 2 gpm nozzle. Also got 4 gpm. All of this is pretty new to me, am I doing something wrong? Also to get the 4 gpm I had to run the pressure to about 180 psi. The manual said to adjust to 100 psi. Any and all advice/help is welcome.
  2. RigglePLC

    RigglePLC LawnSite Fanatic
    Messages: 13,727

    We have a pump expert on here. He will chime in I am sure. Meanwhile--the nozzle does not control the amount you spray--rather it is called a 4 gpm nozzle because at that flow rate the pattern will be consistent and uniform. 3/8 or 1/2 inch hose? How long? Friction loss in a long hose is major. I am thinking 180 pounds is excess. Very hard on the hose and pump. Why do you need 4 gpm? 2 gpm is better for weed control and your tank can go twice as far between fillups.

    But perhaps you plan to mix fertilizer and herbicide like I used to do. 180 pounds is uncontrollable and will probably cause a lot of fertilizer burns. If you can use fertilizer at 3 gals per minute, that should work about right. Reduce the fert concentration in hot weather, or the grass will be toast.
  3. grass4gas

    grass4gas LawnSite Senior Member
    Messages: 591

    I do a little bit of liquid lawn apps using a lesco 200 gal sprayer as well.

    I adjust the pressure to calibrate the nozzle size I use. I write them down and keep em in the truck for reference...no guessing after that.
  4. sandy creek

    sandy creek LawnSite Member
    Messages: 96

    I've got 200 ft. of 3/8" hose. Backed the pressure down to 100psi and put on the 2 gpm nozzle (yellow). Seems a lot more controllable. With the trigger down I've got about 45-50psi on my gauge.
  5. sandy creek

    sandy creek LawnSite Member
    Messages: 96

    Also running the engine at about half throttle....if that makes any difference. Thanks for the replies so far
  6. KES

    KES LawnSite Member
    Messages: 94

    The pressure will drop when you press the trigger. Just make sure you set the engine at a rpm and leave it alone and do all the adjustments with the regulator. Doing this will make sure you are always set up at 2 gpm. I run my engine at half throttle all the time. Make sure to do a bucket check every week.

    Hope this helps.
  7. grassman177

    grassman177 LawnSite Fanatic
    Messages: 9,795

    once you get the gpm right, then you have to get your walking speed down to get that 2 gal sprayed over 1000sqft.

    if you find you dont like the speed at which you have to walk to get that, change the pressure up or down to match the speed you like etc.

    a personal gps speedo cheapy would be good for this, i did not learn that way though.

    also, if you mow too, stripes can be very helpful in knowing where you have sprayed and not, i love to follow stripes. i used to have a diff pace for spraying 2gal per K, one that was a bit faster for following 48in stripes, and one for 60in stripes.

    i sprayed two stripes at a time walking down the middle of them.
  8. Pumptecguy

    Pumptecguy Inactive
    Messages: 71

    sandy creek:

    The nozzle you have is based upon you already having determined you have 4 gpm. It cannot be used as a diagnostic tool to achieve 4 gpm.

    A way to calibrate is to use a ball valve on hose end and close off until your desired gun pressure is reached. Then, measure what that flow is with the bucket, scale and stop watch method. Adjust the regulator back at the pump until you can match the desired flow and pressure at the end of the hose (gun). (you will need a pressure gauge for the end of the hose)

    Do the same for the 2 gpm nozzle.

    An alternative to this is to buy a Spraying Systems '40 and '20 nozzle and calibrate this way. The '40 nozzle will allow 4 gpm at 40 psi and the '20 will allow 2 gpm at 40 psi. These pressures are 22.5% higher at 60 psi.

    The pump/regulator pressure will be higher to overcome the line loss from running all the flow through all that hose.

    I hope this helps. There is helpful information related to this in our Sponsor section.
  9. cgaengineer

    cgaengineer LawnSite Fanatic
    Messages: 15,778

    Unless you have a tach, running the engine at what you think is half throttle and doing it the same each time will be unlikely. Flip the throttle till it stops.
    Posted via Mobile Device
  10. RigglePLC

    RigglePLC LawnSite Fanatic
    Messages: 13,727

    3/8 hose is not really suitable for over 3 gal per min. When the speed of flow through the hose is too high, friction losses become huge.
    If you walk at 3 mph(too fast),--and spray 7 feet wide--you will cover 1800 sqft per minute.

    At 1 mph you will walk 88 feet per minute. At 7 feet wide that is 616 sqft per minute. Too slow. I suggest 2 mph, thereby covering 1232 sqft per minute, (at 7 feet wide). You then need 2.464 gal per minute flow rate. I would estimate you need about 120 lbs pressure, you have to find this by trial and error. But maybe Pumptec can calculate this for you. You are using the Hypro three diaphragm pump, right? Keep motor speed constant. If you install a cut-out switch to stop the motor--you can leave the throttle set at the same place all season, (I did this).

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