# Sprayer calibration math check

Discussion in 'Pesticide & Herbicide Application' started by Jason Rose, Apr 3, 2006.

1. ### Jason RoseLawnSite Fanaticfrom Hutchinson, KansasMessages: 5,858

hey guys, just wanted to run some of my fuzzy math past you and see if you catch any errors here...

Calibrating my sprayer, I built a "walking boom" dual nozzle contraption in hopes to reduce my gallons of liquid per 1,000. The two nozzles combined are putting out 1.5 GPM.

I found that I can cover 1,000 sq. ft. in roughly 35 seconds.

I converted the 1.5 GPM to 192 OZ.PM
192 divided by 60 seconds I get 3.2 OZ per second.
take the 3.2 OZ.PS and multiply by 35 (the number of seconds to cover 1,000 sq. ft.)
I get 112 oz per 1,000 sq. ft. or .875 gallons

That's 114,000 sq. ft. coverage with my 100 gallon tank
I would need 171 ounces of 3 way (lesco) for a 1.5 oz. per 1,000 rate.

If i'm waaaaaaaaaaaaay off here someone hit me in the head and let me know! Thanks!

I know I souuld probably use smaller nozzles and maybe less pressure still and cut back to 1/2 a gallon per 1,000... BUt I hate to mix my tank too hot, I still will have places I need the chemlawn gun to get inbetween stuff, and unless I hit it at a dead run there's no way to run that low of rate with it!

2. ### somo1LawnSite Memberfrom Sw MissouriMessages: 152

The big question is how consistent are you on your walking? Why not adjust your walking speed to get the 1.5gpm that your nozzles are set for?

3. ### eruuskaLawnSite Senior Memberfrom Rensselaer, INMessages: 454

JR,

Looks like the math is good. I wouldn't worry about adjusting the speed, you need to stay at a comfortable, natural pace. You'll stay consistent that way, and that's the important part. You start walking at an unnatural pace just to achieve a nice round number and you'll lose consistency. JMO.

4. ### Jason RoseLawnSite Fanaticfrom Hutchinson, KansasMessages: 5,858

good good... I just did 3 properties with it, looks like I may have OVER calculated how much I was putting down per K. I just used a 3 trial run in my back yard with water, Guess I was walking slower than natural...

I'll just have to "wait and see" what the results are on the 3 I did. The boom works AWESOME! IT covers about a 10 foot swath. I can shoot cracks in concrete 10 foot at a time in half a second shot, lol!

The boom isn't the sturdiest, due to the fact that most of the fittings are nylon and sch. 80 threaded pipe. Had to really improvise to make it work with the nozzle fittings, as they are NOT a standard pipe size.

Compared to flicking the chemlawn gun back and forth and going balls to the wall to spread it out thin, this is EASY. I guess I shouldn't be TOO enthuastic about it just yet, need to run it thru some more lawns first and make sure it dosn't shoot craps on me... I'll have to take a pic of it, I'm kinda proud of my little invention here, lol.

5. ### Jason RoseLawnSite Fanaticfrom Hutchinson, KansasMessages: 5,858

You mean just try to walk the speed to get 1.5 gallons per 1,000? No matter how fast or slow I walk, they are a constant 1.5 gpm. Like eruuska said, you have to walk at a "natural" pace and then just find how much you used in order to calibrate. Scientific it's not, lol.

6. ### GreenUtahLawnSite Senior Memberfrom SLC, UTMessages: 866

I don't think you'd want to change walking speed to makeup for gpm. If anything, you'd change nozzles to a higher flowing nozzle. If you are just spraying weed control, you can take your rates very, very low as low as 8 gals per acre if your boom can spray that precise. (I'd have to check the label for 3-way for ULV rates, but others that probably come from the same spigot will go there) it's a ll a matter of matching nozzles to your rate, just like any other boom application. By the way, walking booms are plentiful in the market, including some very cool covered ones for wind applications. For spot spraying out of the same tank, go to a wand with a gallonage tip to match your rate, no big deal. The same is all true to up your rates if applying fert through the hose as well, to ensure a proper amount of water with your application, increase the tip flow and you are golden.