Misting nozzles come in all shapes and sizes, delivering small droplets to large and everything in between. Choosing the best droplet size for your specific application is sometimes a trial and error process. Getting the spacing correct between them can be done with some simple math.
To calculate the spacing of your misting nozzles, you must first determine how large an area they cover. One factor that greatly affects the coverage is the height of the nozzles above your cuttings. Misting nozzles are designed to be used at specific heights for adequate coverage. Dramm’s Pin Perfect nozzles are best if used between 3 and 5 feet, while Dramm’s JetRain™ nozzles with the red pin should be between 4 and 8 feet. Before beginning your nozzle spacing calculations, you must first find out the optimal height of your nozzles and be sure your nozzle height falls between them.
Before we begin, remember, to get good, uniform coverage from your nozzles they should have a little bit of overlap. Also, once the nozzle is permanently installed in your piping, it is extremely difficult to correct any problems like over or under watering if the spacing is wrong.
I will first use the Dramm Pin Perfect misting nozzles as an example.
The Pin Perfect misting nozzle is designed to cover a 10 foot diameter when 5 feet above the cuttings. The easiest way to determine the spacing for these nozzles is to take the coverage, 10 feet, and divide it in half. So for these Pin Perfect nozzles that are at the recommended height of 5 feet above the cuttings, the distance between the nozzles should be 5 feet.
That was easy wasn’t it? How about if you want to use the nozzles lower than the recommended height? This is just as easy, for a 7 foot diameter spray, the nozzles need to lowered to 3 feet above the cuttings (figures are right from the nozzle manufacturer). Simply divide the coverage in half to get 3 1/2. the nozzles will need to be spaced 3 1/2 feet apart to get the proper coverage.
The nozzle manufacturer will be able to tell you the heights and spacing of your misting nozzles .
Now that you have the basic understanding of how to calculate the distance between permanent misting nozzles, how do you figure the spacing between something like Dramm Mist Stix?
Mist Stix are misting nozzles that are pre-installed onto metal legs that get pushed into the ground and keeps the nozzle above the cuttings. The Stix attach to the main water piping by inserting a small tube into a hole that has been drilled in your water pipe specifically for this purpose. These tubes allow for great flexibility when positioning the Mist Stix. If you discover a dry spot between your Stix, simply pull them out of the ground and move them. The key to this flexibility is getting the holes in the manifold spaced correctly. Dramm offers several different heights of Dramm Stix, and each has different coverage.I personally only use the 36″ tall ones. This allows me to have my Stix high above my cuttings which gives me a larger coverage area. However, if I need a smaller coverage area I simply push the Stix deeper into the ground, effectively lowering them to the height I need. This saves me from purchasing multiple lengths of Mist Stix.
The 36″ tall Stix are designed to be spaced every 42 inches, but what happens if your main water line is an odd length that doesn’t divide by 42? Luckily there is a simple equation for this as shown below:
Now to explain the formula a bit
NOTE: Do NOT drill any holes until you have finished all calculations and they fall within the distances I give.
Let’s say you have a manifold that is 22 feet long. First, you need to figure how many nozzles should fit. Convert the 22 feet into inches. The answer is 264 (22 x 12=264). Next, divide 264 by 42, the optimal distance between the Mist Stix. You get 6.285. You would round that to an even 6.
Now, measure in from both ends of your pipe 21 inches and make a mark with a pencil. This is the location of your first and last holes. I bet you are wondering why you didn’t measure 42 inches because that is the distance between Mist Stix right? You measured 21 inches because it is 1/2 of 42. The Stix will spray the mist 21 inches to the left, and 21 inches to the right for a total of 42 inches.
Now, Take your total length of pipe (264) and subtract 42. The answer is 222 inches; 264 inches minus 42 (21 + 21=42) leaves 222 inches between the two marks you just made.
Next, you need to divide this number by one less than the number of Stix you calculated would fit. Earlier, you calculated 6 Stix would fit the 264 inch long pipe. Subtract one, and you get 5. So, take the 222 (length of pipe minus the 42 inches) and divide that by 5. 222 inches divided by 5 is 44.4 inches. I would round this up to 44.5, or 44 1/2 inches between the holes.
OK, I hear you screaming at me; you said the distance should be 42 inches, not 44 1/2. Remember, 42 inches is the desired distance between the Mist Stix, not necessarily the holes. Nearly any distance between 39 and 45 inches is ok with Mist Stix. The tubes that are attached to the Mist Stix allows great flexibility and the distance between the holes is flexible as well. However, if you came up with a distance of 39 inches or less, or 45 inches or more between holes, there is a simple trick I use. Simply adjust the marks you made at the ends of the pipe and recalculate.
If your calculated distance between the holes was greater than 45, add an inch or two the the initial 21 inch measurement, if it was less than 39, subtract an inch or two. Recalculate the entire formula. You do not need to recalculate the number of Stix that will fit on the length of pipe, just the distances between them. Doing this will change the final distances between the holes. Keep recalculating until the distance between the holes falls within the 39-45 inch range. Once you have successfully calculated the distances, drill your holes.
Permanent installations of misting nozzles should follow the manufacturers recommended heights and spacing. There is very little room for error when installing permanent misting nozzles.
Misting nozzles like the Dramm Mist Stix are more forgiving when it comes to the spacing because of the small tube that is attached to them. This tube allows you to move them in any direction, increasing or reducing the amount of mist your cuttings receive.