Backpack mix and coverage

Discussion in 'Pesticide & Herbicide Application' started by RigglePLC, Aug 17, 2011.

  1. RigglePLC

    RigglePLC LawnSite Fanatic
    Messages: 13,800

    I don't like to guess. I have an SP (Swissmex) backpack sprayer with diaphragm pump. How much does it cover per gallon?

    I sprayed water into a 4 ounce measuring cup, and timed it with a stopwatch, (takes about 13 seconds). Repeated 4 times.
    That equals about .31 ounces per second.

    I then sprayed a concrete drive and measured how much one quart would cover, three times. I converted to square feet per gallon.
    I measured coverage at 773 square feet per gallon--from my backpack sprayer.

    Naturally a lot depends on the pressure and how much you are pumping. And of course the nozzle type on your set up can be different. And there is a chance that the output may vary depending on where you set an adjustable nozzle. And the height where you hold the nozzle could affect the spray coverage. And walking speed and width of swath can vary.

    How much does your backpack cover per gallon? With what nozzle. How many seconds for 4 ounces?

    I just hate it when the new guys just say "Oh, the salesman told me my backpack covers exactly 1000 square feet per gallon."
    Last edited: Aug 17, 2011

    CHARLES CUE LawnSite Silver Member
    Messages: 2,452

    Well my my Stihl backpack gets about 500 sq ft a gal i use 80 deg red even fat tip.

    Never checked how many ounces it puts out

    There's lots of variables with a back pack

    Charles Cue
  3. countryclublawnllc

    countryclublawnllc LawnSite Member
    Messages: 153


    I know that it seems to be very unscientific to just settle on 1 gallon per thousand for any and all backpack sprayers!! Definitely variables such as pump pressure, nozzle output etc etc come into play, but, over the years I've never had a bad experience using that rate as a guide. However, calibration is still recommended on occasion to check. I'm currently using a battery operated Shurflow sprayer that has four adjustable pump speeds so I have calibrated those out. Sounds like your calibration methods and numbers are spot on!

  4. jad004

    jad004 LawnSite Senior Member
    Messages: 282

    I use a piston Solo backpack. I just use the Tee Jet fan tip that comes with the sprayer. It works great for me. I have calibrated the sprayers and 2 get 1/2 gallon per 1000 sq ft and the other one gets 3/4 gallon per 1000 sq ft. I have never measured it per seconds.

    One thing I use is a constanst pressure valve from on my backpacks. It will keep pressure from going above a certain psi and it shuts off if the pressure gets below that certain pressure. This eliiminates one variable factor anyway.

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