How to Choose Misting Nozzles

Look for misting nozzles that balance water pressure and flow rate with your climate.

How to Choose Misting Nozzles

Look for misting nozzles that balance water pressure and flow rate with your climate.

How Do Mist System Nozzles Work?

Misting nozzles are the final step of a system that combines water volume (flow rate) with water pressure to deliver a spray with droplets small enough to cool the air.

A hose or pump pressurizes water and forces it through a nozzle whose small opening (“orifice”) creates a high-speed stream of water droplets. The smaller the orifice, the smaller the droplets. The smaller the droplets, the more effectively the water can cool the air.

Higher water pressure allows the water to exit the nozzle at higher speeds, creating smaller droplets that evaporate more quickly and provide better cooling. Low water pressures can’t force water through the smaller orifices, so lower pressure systems use larger nozzles, which can result in less cooling effect and a wetter mist.

However, higher pressure also means using more water. By selecting an appropriate nozzle size and finding the right balance between water pressure and flow rate, you can ensure that your misting system is both effective and efficient in cooling your outdoor space.

Misting Nozzles and Water Pressure

The size of the water droplets that make up the mist helps determine how much cooling effect you’ll be able to feel. As each little droplet evaporates, it cools the air immediately around it. Bigger droplets take (mili-seconds) longer to evaporate than smaller droplets. If they land on you before they’ve completely evaporated, you’ll get wet. If you’re in fairly dry air this can feel great as the water evaporates off of your skin. But it is uncomfortable in extremely humid weather, or if you just don’t want to be wet. Also any water that doesn’t evaporate must land on something. You’ll need to make sure it doesn’t puddle and that what it lands on is water-safe.

Nozzles for lower pressure misting systems yield larger and fewer water droplets. Fewer, larger water droplets around you cool the air unevenly. You can sometimes feel little spots of cool air surrounded by the unaffected hot air. It can feel like standing by a waterfall or a sprinkler. Nozzles of higher pressure misting systems yield smaller droplets and more water droplets. The air cools more evenly and feels more like a fog. You are less likely to feel the warm air and more likely to simply feel the cooled air. Different number of droplets, different cooling effects.

Reducing the diameter of spray droplets by half increases the number of droplets by eight times. On the other hand, doubling the droplet diameter reduces the number produced by eight times. So, small adjustments with pressure, flow, and nozzle size can make big changes.

You can get an overview of how water pressure affects the amount of cooling you can expect in What Makes a Great Misting System.

Types of Nozzles for Misting Systems

Misting nozzles for outdoor cooling systems produce a fine mist that evaporates quickly and cools the surrounding air. This is different from other nozzles that may create heavy mists or streams of water or other liquids.

Misting Nozzle Mechanisms

Pressure-based nozzles for misting systems can operate at a range of water pressures, from as low as 100 psi (7 bar) to thousands of psi (bar), depending on the exact model of nozzles. They can withstand a wide variety of water qualities.

Impeller-based nozzles are less common, but still very effective. They use a spiral-shaped interior to break up the water into droplets. They typically work at lower water pressures under 100 psi (7 bar). They tend to clog more easily, so water should be thoroughly filtered or treated to remove minerals.

Misting nozzles differ from other nozzles in a few key ways:

  • Flow Rate: Misting system nozzles have a lower flow rate compared to other nozzles that produce a steady stream of water.
  • Spray Pattern: Mist system nozzles produce a fine mist with droplets that are smaller in size and more evenly dispersed than other kinds of nozzles.
  • Material: These nozzles use materials that can hold up to outdoor environments. Stainless steel and brass are commonly used materials.
  • Pressure: Nozzles for outdoor cooling systems generally operate at lower water pressures compared to other misting systems. This creates a more gentle and consistent mist that is better suited for outdoor cooling.

Misting Nozzle Materials

Misting system nozzles are made from a variety of materials, but some of the most common materials include:

  • Stainless steel is often used in misting systems due to its durability and corrosion-resistance, but it can be difficult to install and expensive compared to other materials.
  • Brass is also commonly used due to its resistant to corrosion. It is easy to machine, which can help keep its cost down.
  • Plastic nozzles are a cost-effective option. They are lightweight, easy to install, and resistant to corrosion. They are not durable enough for high-pressure systems and work best with low- and mid- pressure systems. They are not as durable as other materials and may become brittle and crack over time. They are inexpensive enough to replace often, but shards may dislodge and clog the system.
  • Nickel-plated brass is similar to brass in terms of durability and resistance to corrosion, but the added nickel plating provides an extra layer of protection against rust. It’s sometimes used as housing for stainless steel orifices.
  • Ceramic nozzles are very expensive and less commonly used. They are highly resistant to corrosion and are used in high-pressure misting systems. Although they are durable, they are fragile and can break if not handled correctly.

Misting Nozzle Options

Drain valves automatically drain the system each time it is turned off. This helps prevent nozzles plugging up due to calcium buildup, meaning much less nozzle and system cleaning needed. This is especially helpful for large systems or hard to reach nozzles.

Adjustable angle / swivel – Some mist nozzles can rotate or swivel to direct the spray in varying directions. These are helpful with fine-tuning the spray.

Anti drip nozzles and adapters close each time the system is turned off to prevent dripping from the nozzles. Dripping increases mineral buildup on your nozzles. Mist nozzle dripping may not be a problem if the water drips onto concrete or dirt. It could be a problem if it drips onto wood or machinery or guests.

Cleanable –Most nozzles must be removed from the lines in order to clean. But the interior of cleanable nozzles can be removed for cleaning and then replaced back into the exterior which stays in the lines.

Extensions – These can extend the mist of your system by as much as 18″.

Multiple orifices in one nozzle allow for spray in several direction at once.

Replacement heads allow you to replace damaged or clogged orifices without having to remove and replace the entire nozzle.

How Many Gallons per Hour Does a Misting System Use?

Flow Rate / Water Volume and Nozzle Size

The size of the mist nozzle orifice (opening) balances with your misting system’s water pressure and flow rate (amount of water) to create a cooling mist. Nozzles typically spray less water at lower pressures than at high pressures. But because the spray droplets are larger, they will not feel as cool.

In fact, certain mist nozzles will not work at all at lower water pressures. As the water pressure at the nozzle increases, the flow rate through the nozzle increases. The higher the water pressure, the smaller the nozzle opening you’ll need.

It will help to decide on the water pressure you want your system to use before selecting the mist nozzle.

We cover the other misting system component in our series on the 3 Parts of a Misting System:
1. A Misting Pump – the heart of a strong misting system.
2. Lines & Fittings that tie it all together.
3. Nozzles (this page) is the third component.

Also see our pages on:

Estimating Costs – helps before you purchase a system, and can help you estimate operating expenses.

Finally, Installation Tips and Maintenance Tips will help you with some “nuts & bolts” issues.

The larger misting nozzles will work well with low- and medium-pressure misting systems. The smaller misting nozzles should only be used with high-pressure systems. If you select too large a nozzle for your water pressure, the pump won’t be able to send enough water through it to create a fine mist. If you select too small a nozzle, the over-supply of water through the nozzle may “over-pressure” the pump and damage it. It’s not a matter of “more is better” but of balance.

Sample Droplet Sizes

Here is a sampling of water droplet sizes based on common nozzle sizes using 1000 psi / 70 bar. Water droplet sizes are measured in “microns” (1 micron is .001mm). To give you a size reference, 100 microns is about the diameter of a human hair. The largest of these droplets is just under half that.

  • .020″ / .5 mm – the droplets range from 9.5 microns to 49.9 microns
  • .016″ / .4 mm – the droplets range from 3.8 microns to 47.9 microns
  • .012″ / .3 mm – the droplets range from 1.6 microns to 39.1 microns (a commonly used size for dry climates)
  • .008″ / .2 mm – the droplets range from 1.4 microns to 37.9 microns (this smaller size is better for more humid climates because its smaller drops adds less humidity to the air)
  • .006″ / .15 mm – the droplets range from 1.2 microns to 36.4 microns (this smaller size is better for more humid climates because its smaller drops adds less humidity to the air)

Example of a flow rate chart

Misting nozzle manufacturers publish flow rates for their nozzles in gallons or liters per minute (GPM or LPM) or per hour (GPH or LPH) as it relates to different water pressures. Most spray nozzles have their own charts that show their flow rate at one or more water pressure. An example chart is below. Some charts, like this one, are for general information — these flow rates are not for any particular nozzle. Ask your nozzle supplier for charts on specific misting nozzles.

The nozzle’s flow rate should align with the system pump’s flow rate.

PSI / BAR60 / 4.080 / 5.4100 / 6.8125 / 8.5150 /10200 / 14300 / 20500 / 341000 / 70
SIZE
.020″ / 05mmGPH 1.802.102.402.702.903.404.105.307.40
LPH6.817.959.0810.2211.0012.8715.5220.0628.01
.016″ / .16mmGPH1.201.401.601.701.902.202.703.504.90
LPH4.545.306.076.447.198.3310.2213.2518.55
.012″ / .3mmGPH.8901.101.201.401.501.702.102.703.78
LPH3.374.164.545.305.686.447.9510.2214.31
.008″ / .2mmGPH1.051.351.89
LPH3.975.117.15
.006″ / .15mmGPH0.580.80
LPH2.203.03
Chart shows flow rates in Gallons Per Hour and Liters Per Hour for 5 common nozzle sizes at several different water pressures in PSI and BAR

Differences in flow rate between nozzles sizes are smaller at lower pressures and bigger at higher pressures. Using the smallest nozzles your system’s pressure can handle will minimize water use and costs while increasing the cooling effect. Notice that the smallest nozzles won’t work with lower water pressures.

General Rule of Thumb:

Nozzle flow for 500 psi (34 bar) equals 75% of the rated flow of 1000 psi (70 bar);
nozzle flow for 250 psi (17 bar) equals 50% of the rated flow of 1000 psi (70 bar).

Spray Pattern / Mist Nozzle Spacing

Misting nozzles create a spray that angles out anywhere from 40° – 100°, depending on your system’s water pressure. The wider the angle, the more area the spray will cover and fewer nozzles are needed. 18, 24 or 30 inch nozzle spacing is standard, but some suppliers will customize spacing to your needs. Nozzle spacing in plastic, nylon, and copper lines can be easily customized during installation.

For maximum cooling effect, it makes sense that you would want a fairly dense curtain of mist. But there is a point at which the system simply cannot make you any cooler, no matter how closely the nozzles are spaced. In fact, over-spraying an area will simply make it wet, even with the smallest of nozzles.

If you need more cooling, consider combining you misting system with other cooling methods.

The final determination of how closely to space the misting nozzles in your system will be based on:

Nozzle Spacing Balances Science with Preferences

Your system’s water pressure, flow rate, your choice of nozzles, your climate, your system’s configuration and the shape of the structure it is mounted to, even your personal preferences all combine to make a system that is uniquely yours. Your misting system supplier’s experience is invaluable in determining how far apart to space the nozzles. If installing it yourself, use one of the standard spacings (18, 24, or 30″) and adjust it based on how many misting nozzles your system can handle. You can make spacing adjustments after installation, if necessary. These adjustments will be easier to make in some line materials than others. Review the page on line materials for more info.

Too Many Nozzles Make a Misting System Less Effective

The number of misting nozzles any misting system can handle varies depending on the pump, the type of nozzles used, corresponding flow rate, the number and types of fittings. Too many nozzles can cause a noticeable drop in performance. Most kits will tell you how many nozzles they can handle. Fewer nozzles mean less water used but more nozzles can mean more cooling. Remember, a misting system is a matter of balance.

Other Outdoor Cooling Methods

Take a look at our comparison page or our pages on other outdoor cooling methods.

While misting systems work well on their own, they can combine with other cooling methods, such as outdoor fans for added cooling effect. Misting fans are a clear example of how misting systems work with another cooling method to maximize cooling. Outdoor shades are a nearly universal solution that work well with any outdoor cooling method.

Swamp coolers (desert coolers) use a similar technology as misting systems, but in a contained unit.

Portable air conditioners are especially suited to enclosed areas and special circumstances.

For some surprising tips on what to look for in a great misting system, take a look at Selecting a Misting System.