Spray Nozzle Selection

So, you need to replace a Spray Nozzle?

Eventually the time will come when your sprinkler system will need a spray nozzle replaced.  Maybe the coverage isn’t right and you are hoping to fix a brown spot; perhaps the nozzle got clogged and is now spraying funny; or maybe the nozzle went missing and has now left you with a sky-high geyser of water instead of a sprinkler.  

Whatever the reason, don’t worry!  Smartirrigation.com is here to walk you through and simplify the details in selecting the proper spray nozzle for your irrigation system to get your system back to running at 100%!

In this article, we’ll be focusing on how to select and replace a spray nozzle, which is different from the spray body that it is attached to.  

The spray body connects to the water line and includes a spring-loaded riser that pops up when the water is turned on.  The spray nozzle is the specially-shaped water outlet that is screwed onto this riser*A few uncommon spray bodies actually have the spray nozzle built-in as all one part.  If this is the case, you will need to replace the entire spray body rather than just the nozzle. and can be replaced independently from the spray body.

In a different article [coming soon], we will cover how to replace a spray body if it is leaking or if the riser is broken.  But for this article, we will assume that the existing spray body is OK and that we can thread a new spray nozzle onto it.

You can also watch our videos on adjusting spray nozzles below:

What type of sprinkler nozzle needs replacing?

Before replacing the nozzle, the first thing we need to do is determine if the sprinkler we are working on needs a spray nozzle.  Assuming your system was designed properly (see our Design Article coming soon), we want to install the same type of nozzle that was on there before.  Most sprinkler zones do not mix sprays with other types of sprinklers.

Therefore, we can find which type of nozzle to install by looking at the other sprinklers running on the zone, or even looking at the old nozzle if you can find it.  The following description and pictures should help you out: 

·    Spray Nozzle: fan-pattern spray that doesn’t move
This is the type of nozzle we will be replacing in this article!  These sprinkler heads do not have any moving parts and put water down very quickly (run times are typically 10-15 minutes).  The sprinkler consists of a spray nozzle that is threaded onto a spray body.

·       Rotary Nozzles: multiple streams of water that rotate
While these nozzles also fit onto a spray body, they are actually a different product that waters differently and has its own selection considerations [article coming soon].  Therefore, these nozzles are not dealt with in this article.

·       Rotors: single stream of water that rotates
These sprinklers actually don’t even use a spray body!  As you could imagine, changing their nozzles or repairing them is therefore a very different process than what we review in this article.  If you need to repair your rotor sprinklers, check out this article instead [coming soon]!

Which Nozzle to Select?

OK, so you’ve determined that you need to replace a spray nozzle for your sprinkler.  Now you need to figure out which nozzle to actually put on.  But we need to be careful: a system can be adversely affected if you choose a nozzle that uses too much water or doesn’t cover the grass properly. 

The easiest way to choose your replacement nozzle is to simply match it to the old clogged or broken nozzle (or missing nozzle, if you can find it).  Most of the information is actually stamped right on the top of the nozzle!  As long as the sprinkler was watering properly before, you can keep things working the same by using the exact same nozzle.

However, if you can not find the old nozzle or were not happy with the old performance, you will need to pick out a new one.  But there are actually many different nozzles available, so which is the best nozzle for the particular area?  Thankfully, the perfect irrigation spray nozzle can be found by answering a few questions:

1) Spray Shape

Almost all spray nozzles water in a circular pattern, either a full circle or some portion (“arc”) of a circle, such as a quarter circle.  

There are also a few specialty spray nozzles that spray in rectangular patterns.  However, you won’t need these unless the area being watered is a thin strip and are discussed further down (but the following questions are  relevant for those heads too).

For most situations, you will just need a regular spray nozzle that waters in a circular arc and can move on to the next question!

2) Spray Radius

The most important question to ask is how far you need your sprinkler to spray?  This is because each nozzle is only designed to spray a specific distance*Spray nozzles *do* have an adjustment screw at the top that can be used to reduce the spray distance, but this decreases the spray quality and evenness and is NOT a replacement for selecting the proper sized nozzle..  Common spray distances for these nozzles are 8′, 10′, 12′, and 15′ *Other special radii are also available, depending on the manufacturer.  This includes short-radius nozzles spraying 2′ – 5′, as well as long-radius nozzles spraying 17′ – 18′..  This is the number that is stamped on top of the spray nozzle.  The color of the spray nozzle also typically indicates its spray radius to help with easy identification, although different manufactures use different color codes.

So which spray distance do you need?  Proper design is based on head-to-head coverage, so you want one sprinkler spraying right up to the base of the next closest sprinkler*This is different from “pattern-to-pattern” coverage, where the spray patterns of nozzles meet but do not overlap.  This design leads to very uneven coverage and is not recommended..  However, sometimes there are areas that you don’t want to be watered, so the spray distance really depends on your individual situation.  

Once you know how the furthest point you want your sprinkler to spray, measure out the distance back to the spray head (you can even just pace it out) and then select the nozzle radius that most-closely matches this distance.

The further a nozzle sprays, the more water it uses! Each sprinkler zone can only supply a limited amount of water, so putting in too large a spray nozzle can wreck an entire zone by using more water than the zone can supply.  Therefore, don’t use larger nozzles than necessary.

Greater detail on zone water supply and the water usage of specific heads can be found in our Design article [coming soon]. 

3) Fixed Arc vs Adjustable Arc

The next question that needs an answer is what portion of a circle this spray needs to water?  For example, sprays in a 90° corner only need to water in a quarter circle.  This portion of a circle is called the spray’s “arc” and is represented by a letter typically stamped on top of the spray nozzle.  The spray arc of a nozzle can be either fixed or adjustable.

Fixed Arc
These nozzles only spray in a single arc pattern and have letters like Q (quarter circle), H (half circle), and F (full circle) stamped on their tops. The advantage of fixed arc nozzles that they are engineered to water a specific arc very evenly, accurately, and efficiently, which reduces brown spots and saves money.  The disadvantages are that you must carry a completely different nozzle for each arc pattern, and that they will over/under spray if the lawn is shaped with odd angles that don’t match these fixed arcs. 

Adjustable Arc
Each one of these nozzles can cover any portion of a circle, from a 5° wedge to a full circle, and are sometimes stamped with an “A” on top.  The advantages of adjustable arc nozzles are its ability to water odd angles without overspray, and that you only need to carry one nozzle of each radius to cover every arc pattern. The disadvantages are that their coverage is less even (“jack of all trades, master of none”), and most use substantially more water than fixed arc nozzles for a given coverage pattern.  This high water usage can actually ruin the coverage of an entire zone if it exceeds the zone’s maximum flow rate.

Generally, we recommend using fixed arc spray nozzles whenever possible.
Due to their more even coverage and lower water usage, our experience has shown that the inconvenience of carrying 4x the nozzles is outweighed by the benefits to the irrigation system and the lawn.  We do, of course, use adjustable arc nozzles when the shape of the lawn requires it.

That said, there are newer adjustable arc spray nozzles, such as the Rainbird HE-VAN nozzles, that have the same water usage as fixed arc nozzles and have improved coverage efficiency.  This season we are planning on conducting a scientific comparison to determine if these HE nozzles provide an effective alternative to fixed arc nozzles. 
Stay Tuned for our comparison!

4) Thread Style

Finally, you have to make sure that the threads of your selected spray nozzle compliment the threads on the spray body.  Threaded sprinkler parts are conventionally classified as either male or female.  Female threads are recessed inside the fitting, while male threads are on the outside of the fitting, and one of each styles of threads is needed to join parts together. 

Spray bodies are most commonly male-threaded, which means that you will typically need to purchase female-threaded spray nozzles.  But make sure you check with the spray body just to be sure!

5) Specialty Sprays

Strip Patterns
Some special spray nozzles actually do NOT spray in part of a circular pattern!  These are called “strip pattern” sprays and are designed to water narrow areas.  The location of the sprinkler will determine the type of pattern you will need.  While naming and available spray patterns may vary between brands, one standard strip pattern is the 15′ Side Strip (labeled “15 SST”, “SS 530”, etc), which sprays 5′ forward and 15′ to each side.

Matched Precipitation Rate (MPR)
Some spray nozzles are MPR, which means all of those nozzles will provide the same amount of water to the lawn regardless of how far they spray or their spray arc.  These sprays, such as the Rainbird MPRs or HE-VANs, take the guess work out of even coverage when using different nozzles.  Otherwise, be sure to check and plan for the precipitation rate of each nozzle on the zone. 

Low-Flow Sprays
If your system has lower pressure, or if you have a lot of sprays on one zone, but still desire the shorter run-times of sprays compared to rotary nozzles, a middle ground is low-flow spray nozzles, such as the Toro Precision Spray nozzles.  Just make sure you adjust your run times to account for the slightly lower precipitation rate.

Time to Install the Spray Nozzle!

After making it through those 5 questions, you have now selected the proper replacement spray nozzle for your sprinkler system!  Actually, you’ve just selected a better spray nozzle for your sprinklers than many inexperienced contractors would, so congratulations! 

You can now go out and purchase this nozzle at your local irrigation or landscape store, or even order it online!  Once it arrives, you can finally install the nozzle – and make sure you don’t forget the filter screen.  If you would like some tips on installing sprinkler spray nozzles, we cover that as well in our article [coming soon], or watch our videos below.

And remember, if you still have questions, your local certified irrigation technician is only a call away!

Happy Watering!

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