How to get an estimate of how many misting nozzles per zone you can use.
To get a good understanding of how many mist nozzles you can use per zone with your mist system, you have to do a little groundwork first. This is not a 100% accurate method, but will work for you to get an estimate of the number of nozzles you can use. This method assumes you are connecting your misting system to an outside spigot, are using schedule 40 pvc water piping, and will be operating only one zone at a time. If you plan on operating two misting zones at one time, complete these steps and divide the number of misting nozzles by 2 to get an idea on how many misting nozzles per zone you can use.
First you need to determine your water pressure, your flow rate at the spigot you will attach your system to, and lastly determine the size of the pipes that are delivering the water to your misting nozzles. When figuring the flow rate, stick with one unit of measure throughout the entire process. If you choose gallons per minute, use the gallons per minute number for all calculations.
How to figure out your water pressure.
You must first gather the components needed to build a simple pressure gauge that will attach to your spigot. See the following picture to see the one I made and to get an idea as to what components will be needed and how to assemble it. I purchased a hose adapter that attaches directly to the spigot and has 1/2 ips female threads on the other end. I then purchased a 100 psi gauge that had 1/8 ips male threads. I then had to purchase two more reducing fittings to adapt the gauge to the garden hose adapter. Be sure to use pipe thread sealant on all threads when assembling the components.
To get the water pressure at the spigot you must first be sure everything that uses water in your home is turned off. Dishwashers, clothes washer, faucets, etc. all need to be off. Install your new pressure gauge on your outside spigot. Next, turn the water on at the spigot and note the pressure reading. Gather pressure readings throughout the day and write them down. We will be using the lowest pressure reading you took. The ideal water pressure for your misting system will be between 30-50 psi. Lowers pressure will not deliver enough water to your misting nozzles and may result in poor performance. Too high water pressure will result in stress on all your components and may cause failures of solenoids or misting nozzles. Booster pumps can be used for pressures that are too low and pressure regulators can be used for high water pressures.
How to figure out your water flow rate.
NOTE:While gathering the flow rates, You should calculate everything as gallons per minute (GPM). To convert gallons per hour (GPH) into gallons per minute (GPM) simply divide the number by 60.
The flow rate is the ultimate determining factor on how many misting nozzles you can use per zone. The amount of water that can flow through your water pipes at any given time is called the flow rate, and is usually given as gallons per minute(GPM) or gallons per hour(GPH). Larger pipes can allow more water to pass through them than smaller pipes, and most homes have a mixture of large and small pipes, so an accurate test at the spigot is needed. You need to determine how much water can pass through your outside spigot that will be supplying the water to your misting system. Each misting nozzle is designed to deliver a given amount of water and you need to determine how much water your spigot can supply to determine how many mist nozzles can be used.
Find a bucket that will hold at least one gallon of water. Add one gallon of water to the bucket. The best way to get an accurate gallon is to use a milk jug or similar container, fill it and transfer the water to the bucket. On the inside of the bucket, place a mark at the one gallon mark. Dump out the water and hold the bucket below your outside spigot. You will be opening the spigot all the way and timing how many seconds it takes to fill the bucket to the gallon mark. Divide the number of seconds into 60. This is your flow rate in gallons per minute (GPM). If you figured gallons per hour (GPH), divide your number by 60 to convert it to GPM. Write these flow numbers down.
On average, a 3/4-inch hose can deliver 23 gallons of water per minute, while a 5/8-inch hose allows 17 gallons per minute. Determine your hose size and write down your garden hose flow.
Next, take a good look at your water delivery piping for your misting system, and use the piping size chart to determine it’s flow rate.
Find the pipe size and flow rate for your water pipe.
Now that we have a bunch of numbers written down, here is how we are going to use them to determine how many misting nozzles we can use per zone on our misting system:
Compare the flows of your spigot GPM, your garden hose GPM, and water piping GPM for your misting system. Choose the lowest of the numbers. This is the maximum flow in gallons per minute(GPM)of your misting system and we can now use this number to determine how many misting nozzles can be used per misting zone.
Find the flow rate of your misting nozzles. If you are using Dramm nozzles, consult this mist nozzle chart. If you are using misting nozzles from a different manufacturer, you will need to reference the literature that came with the nozzles, do a Google search for the info, or call the manufacturer for the flow rate. Using the chart, find the flow rate of the mist nozzle you are using. Note that the charts give the flow in gallons per minute (GPM). If your nozzle flow is given in GPH, convert it to GPM by dividing the number by 60.
Take the lowest flow number of your system that you determined earlier and divide it by the flow of a single misting nozzle. This resulting number is the maximum number of misting nozzles you can use per zone.
Here is a quick calculation to help show how it is done:
Pressure: 40 psi
Flow rate at spigot: 10 GPM (600 GPH)
Hose flow rate: 5/8= 17 GPM (1020 GPH)
Water piping flow rate: 3/4 PVC=8 GPM (480 GPH)
Remember to convert all GPH figures to GPM!
The pressure is within tolerance so you do not have to do anything.
Of all the flow rates, the piping is the lowest at 8 GPM, so that is the figure you need to use.
Referring to the nozzle charts, you find that the Green Pin Perfect misting nozzles flows 1.08 GPM at 36 psi.
Now, divide 1.08 into 8 to get 7.4. So this means that you can safely use 8 (I rounded up) misting nozzles per zone as long as you only operate one zone at a time.
So looking at these figures, if you wanted to increase the number of misting nozzles your mist system can use, you could simply increase the water piping of the misting system to 1″, and you could then increase the number of nozzles per zone to 10 because the spigot now has the lowest flow rate of 10 GPM, which equals roughly 10 nozzles per zone.
Remember, this is a basic calculation and is to be used to get an estimate of how many nozzles can safely be used given your water flow rate. Don’t be afraid to experiment, but be sure not to make permanent changes until you are absolutely sure of the outcome. You may find that you can use more nozzles than this calculation suggests, or in some cases, you may need to use less.