This article is intended to give you an introduction to the various sprinkler heads used for irrigation. It will help you choose the best sprinkler for your situation. At the same time it will warn you away from some common and costly errors often made in sprinkler head selection. Similar information on bubblers is found in the last section of this page.
Types of Sprinklers:
Traditionally sprinkler heads are grouped into two broad types based on the method they use to distribute the water, spray type sprinklers and rotor type sprinklers. However new technologies are blurring the traditional boundaries between the types.
More properly called “fixed spray heads” these are the small heads that spray a fan-shaped pattern of water. Think of a shower nozzle. Most use interchangeable nozzles installed on the sprinkler which determine the pattern (1/2 circle, full circle, etc.) and the radius of the water throw. Some specialty patterns are available for long, narrow areas. Spray heads are spaced up to 18 feet apart. The basic physics of water spray limit the distance between heads. They need between 20 and 30 PSI of water pressure to operate properly.
Rotor is the term used to describe the various sprinklers which operate by rotating streams of water back and forth or in circles over the landscape. The example which most people are familiar with is the “impact” rotor sprinkler (often improperly called a “rainbird*”) which moves back and forth firing bursts of water. You probably know this sprinkler best for the distinct sound it makes when operating– tooka, tooka, tooka, tic, tic, tic, tic, tic, tooka, tooka, tooka, etc… The impact rotors are rapidly being replaced now by gear driven rotors which are very quiet, lower maintenance, and much smaller in size. It won’t be long before the average person has no clue what I am describing! These new turbine and gear driven rotors have one or more streams of water which move silently across the landscape. The prettiest of these are the “multi-stream rotors” where multiple streams of water rotate over the landscape one after the other. Multi-stream rotors are fascinating to watch. Rotors can be spaced from 8 feet to 65 feet apart. There are rotors available that can be spaced farther apart than 65 feet but I don’t advise using them in most situations, even golf courses are moving away from using them due to problems. The traditional rotors with spacings over 20 feet require a lot more water pressure to operate than spray heads. Here’s a rule of thumb, “The water pressure at the rotor head in (PSI) must exceed the distance (feet) between the heads.” (Known as Stryker’s Rule, admittedly that’s a little ego stroking on my part, but I did create the rule!) Thus if you want to space rotors 35 feet apart you will need 35 PSI of pressure at the sprinkler head. That means you will probably need around 45 PSI minimum to operate the system since pressure will be lost in the pipes and valves as the water flows to the sprinklers. More on that later. The small 3/4″ inlet rotors sold for residential use work best at 25 to 35 foot spacings.
(* Rain Bird is the name of a sprinkler company and is a registered trademark. The Rain Bird company makes many different types of sprinkler heads, including impact rotors. They also many other irrigation products.)
Rotary Nozzles & Rotators:
A new type of miniature rotor has been introduced in recent years and have become extremely popular. These are often called rotary nozzles or rotator nozzles. The first brand on the market was called the “MP Rotator”, and several other similar products quickly became available from other companies. Most manufacturers classify these as a “spray heads” in their catalogs. They are called rotary nozzles because they are a very small rotor that is the same size as the standard nozzle on a spray-type sprinkler. Thus they fit onto the smaller, and less expensive, spray head pop-up bodies. Rotary/rotator nozzles are more efficient than traditional spray heads because they produce less “mist” that evaporates before it reaches the ground. Thus they are often promoted for use in place of standard spray heads by water conservation agencies.
These rotary nozzles have a radius generally between 15 and 35 feet*. The exact distance depends on the model. They all use multiple streams of water that rotate around the nozzle and look like rotating spider legs.
*New models are being introduced each year as the technology advances and I expect to see shorter radius rotators available. Already there are add on devices like the Little Valve brand devices that will reduce the radius of a rotator.
A few words of caution on rotary/rotator water savings claims:
Keep in mind that the water savings are primarily found when comparing rotators to spray heads. For spacings over 20′ it is typical to use rotors rather than spray heads. I haven’t seen any independent lab data that suggests that using a rotator nozzle in place of a rotor head will save water. (As of 2013.)
Like all other claims you must compare apples with apples. I once had a city official, who obviously had just been visited by a rotary nozzle salesman, order me to replace all the sprinklers on a shopping center irrigation system with “rotators”. The planters I was watering were 6 feet wide, and at that time the smallest rotator on the market had a minimum radius of 15 feet. Thus if I had done as he suggested I would have been watering 9 feet of the parking lot! Not a good move if you want to save water… The moral of the story is that you need to use your head and select the right product for your situation. Replacing a 6′ radius spray head with a 12′ radius rotator is NOT going to save any water! Yet I hear that same blanket statement “switch to rotators and save water” over and over.
Guide to Selecting the Right Sprinkler Type:
Which to use, sprays, rotary nozzles, or rotors? Here are some questions to guide your selection.
- Is your water pressure less than 40 PSI static? If so you should consider using sprays or rotary nozzles.
- Is the area long and narrow, between 12-28′ wide? Then you should look into rotary nozzles. They may also be appropriate for narrower areas, at the time I am writing this Hunter has introduced a “side-strip” rotator for 4 to 5 foot wide strips that are at least 12′ long. More combinations of widths will likely be introduced in coming years.
- Is the area you want to water greater than 30′ x 30′ in dimensions? If so, rotors may be the best solution.
- Is the edge of the area to be watered curved? If the edge has sharp curves (less than 20′ radius) then rotors with longer radii will have difficulty watering the edges without over-spraying them. This may not be an issue depending on what is beyond the edge. If the area beyond the edge should not get water on it you might want to consider a smaller rotary nozzle or spray-type sprinkler.
Installation Issues related to Sprinkler Selection:
Rotors and rotary nozzles are spaced farther apart than sprays. Therefore installation of them requires less pipe and trenching, but they also cost more per sprinkler. For most normal-size city residential yards spray heads or rotary nozzles are usually the better choice.
Cost Issues in Selecting Type of Sprinkler:
Surprisingly regardless of the type of sprinkler you use, the cost per square foot of area irrigated comes out about the same, assuming correct design of course. When using rotors or rotary nozzles there is less pipe and trenches, but the rotors themselves cost more. Spray heads are less expensive to buy, but they require more pipe, trenches and valves to install. In the end, the price really comes out pretty close either way.
Note: If your static water pressure (“design pressure” on your Design Data Form) is less than 40 PSI rotors will not work properly, DO NOT USE THEM. See the previous pages of the Sprinkler System Design Tutorial if you don’t know what static water pressure or design pressure means. If you have a well and pump you must have your pump-on setting adjusted to no less than 40 PSI if you plan to use rotors. A “40-60″ setting is typical. Contact your pump company for assistance.
If you are unsure, try using rotors in your design. If they don’t work out well, then erase them from your plan and try rotary nozzles. In many situations the best option maybe to use rotors in large areas, and spray heads or rotary nozzles in smaller or more narrow spaces. So you may have a mixture. This is OK, but there are some things you need to be careful of when mixing different types of sprinklers. The first is that each type must be separated and connected to a separate control valve. You can’t mix the types together on a single valve circuit or valve zone. More on this later in the tutorial. The second is determining how to space the heads where the different types meet each other. For example, if you have a 30′ radius rotor next to a 15′ radius spray head, how far apart should they be from each other? There are many different schools of thought on this, but my general recommendation is to split the difference. In this example put them 22′ apart. Yes, the rotor would overspray the spray head by a considerable distance. But if you put them 30′ apart you will get a distinct dry spot between them.
Basic Body Styles:
Pop-Up Style Sprinklers:
Pop-up style sprinklers are installed below ground. A piston that contains the nozzle lifts up from the sprinkler body when the sprinkler is operating and then retracts back below ground when not in use. Consider using pop-up style heads even in shrub areas. Pop-up sprinklers often don’t cost any more than shrub sprinklers when you include the cost of the riser (the upright pipe the sprinkler is mounted on). Two major advantages of pop-up sprinklers are safety and appearance.
What Pop-up Height Should You Use?
Pop-up style sprinklers are available in a variety of heights, generally 2″, 3″ , 4″ 6″ and 12″ are the common heights. Most of my commercial clients ask me to use at least a 6″ height, even for lawns. The extra height avoids problems. I wouldn’t use anything less than 4″ on fescue, rye, St. Augustine, or bluegrass lawns. For close mowed Bermuda grass 3″ will work. My experience is that the spray from 2″ pop-up heads are often blocked by even recently mowed grass! For that reason I do not recommend any model of 2″ pop-up, you will get dry spots in the lawn. For groundcover and shrubs use 6″ and 12″ heads.
Groundcover Design Trick:
Here’s a tip for watering a groundcover area next to a lawn. Place the sprinklers for the groundcover about 12″ away from the groundcover, in the lawn area, and aim them back at the groundcover. That way the groundcover does not block the spray as easily.
Shrub Style Sprinklers:
Shrub style sprinklers were a type of sprinkler head designed to be installed above ground on top of a pipe. In the old days they were used for shrub areas, thus the name. For liability reasons, most irrigation professionals no longer use shrub sprinklers, except in very limited situations where nothing else will work. You should take a hint from the pros and also avoid using them! Read the warning below! (For shrubs you really should look into using drip irrigation, it is a better choice than sprinklers for most situations.)
Many people are injured each year when they trip over, or fall on, shrub style sprinklers. Think Safety. Do not use shrub style sprinklers unless a very tall riser is needed to raise the sprinkler spray over the tops of tall shrubs. When needed, shrub style sprinklers should only be used in areas well away from sidewalks, patios, and areas where children play. They should be clearly visible. A good idea is to strap them to a large post, like a 4″x4″ wood or plastic fence post, to hold them stable and make them easy to see.
Metal or Plastic?
At the grocery store it’s “paper or plastic?” but with sprinklers the question becomes “metal or plastic?”. The conventional wisdom is that metal is more durable than plastic, and therefore is better. Up until the late 1970′s metal (usually brass, sometimes zinc) was the standard material from which almost all sprinklers were made. However, times have changed and now plastic is the most common material for sprinklers. Very few manufacturers even bother to make an all-metal sprinkler anymore. The primary reason for this change in materials is cost; machined metal parts are enormously expensive in comparison to injection molded plastic. Fortunately, most of today’s plastic sprinkler heads are very well engineered and will perform as well as, if not better than, the old metal sprinklers.
Hybrids: A few companies manufacture plastic sprinkler bodies which accept brass nozzles, which they claim results in a better water pattern. Other manufacturers claim that plastic nozzles perform as well as brass. The research tends to indicate that a really well-machined brass nozzle has better water distribution. But that’s laboratory tests, and in the real world a lot of other factors come into play. I personally haven’t noticed any significant difference in performance between most brass and plastic nozzles in well-designed, sprinkler systems, although brass nozzles will no doubt last longer. More importantly, there are a few nozzles, both brass and plastic, which don’t seem to perform as well as others. Fortunately, they are easily identified by comparing prices (as in “you get what you pay for.”) Typically these bad nozzles come pre-installed on sprinklers that don’t have the features I list below, so if you stick to sprinklers with my recommended features you will get acceptable quality nozzles.
Features to Look For:
The following features are common to all good-quality sprinkler heads (for both rotors and spray type heads.) Choosing a sprinkler without these features is asking for trouble.
- Spring Retraction: Make sure a spring is used to pull the pop-up piston down into the case when the sprinkler isn’t on. As a general rule the stronger the spring, the less likely the piston will “stick up” and get mowed off. Stay away from sprinklers that rely only on gravity to retract the pop-up piston.
- Wiper Seal: This is a soft plastic seal around the pop-up riser stem that seals the riser so it won’t leak . The wiper seal also is responsible for keeping dirt out of the sprinkler body, and is the most important part in determining how long the sprinkler will last. Make sure the sprinkler model you select has a wiper seal. Note: on some sprinklers you must remove the sprinkler’s cap and look inside the bottom of it to see the seal. Be careful when removing the cap, on some models the spring will shoot out!
- 3 Inch Pop-Up Height (or higher): Unless you just like to trim grass around sprinkler heads, make sure the pop-up height is 3″ or more. This way the spray nozzle will clear the top of the grass. Most professionals use 4″ pop-up sprinklers in lawn areas, and 6″ or 12″ pop-ups in shrub areas.
- Rat Traps. This is a design type to avoid if you can. A “rat trap” is a derogatory name used in the sprinkler business to describe any sprinkler with a design that allows debris to fall into the sprinkler body when the riser is raised. The more proper name is a “bucket” style body, but I like the visual image of the problem that rat trap provides. The debris collects in the bucket area and eventually there is enough garbage in there to prevent the mechanism from dropping back down. The stuff that falls in there can get pretty ripe smelling as it decomposes, too! Do rats really get trapped in them? I’ve never seen one. The “trap” only opens when the sprinkler is operating and rats tend to stay away from a sprinkler that is operating! Mostly grass clippings and dirt get trapped.
Sprinkler Make and Model Recommendations:
Mix and Match. One common question I get from users of this tutorial is “who makes the best sprinkler heads” or “which model should I use?” This probably won’t help you much but most of my designs have a mixture of brands and models as I feel different products are best for different situations. But what you should get out of that is that it is OK to mix and match– within limits. On any single valve circuit you should use one brand and model of sprinklers only. This is because precipitation rates vary between makes and models and if you mix a high precipitation sprinkler on the same valve zone as a low one you will get mud in one area and dry spots in another. But you can create two different valve zones and use different sprinklers in each. So one valve might turn on a group of brand X rotors to water a large lawn area. Another valve might turn on a group of brand Y spray heads to water a small lawn in a parking strip. And a 3rd valve might turn on a drip system using brand Z emitters that waters some shrubs.
Brands and Models. While I don’t recommend specific brands of equipment, I do have a few irrigation product reviews you might want to look at. I try to be as objective as possible and I do present hard facts when I have them (like results from tests on my sprinkler test stand,) but my tests aren’t statistically relevant (I can’t afford to buy and test sprinklers from 30 random stores and random times in order to get a statistically solid sampling.) So the reviews are mostly my personal opinions. If you get 4 industry pros together you will get 4 different opinions of products, each a heartfelt honest opinion. I try to focus on products sold to retail customers at hardware and home stores. I figure other pros aren’t looking for my opinions!
More on selecting your sprinklers is coming later on in the tutorial. At this point in the design process what you need to know is an approximate sprinkler operating pressure. You may have noticed I used the term “operating pressure” here rather than “pressure loss” as previously used for other irrigation equipment like valves and backflow preventers. While pressure loss is a perfectly accurate term for the pressure used by sprinkler heads and emitters, operating pressure is more commonly used. Operating pressure is simply the pressure that needs to be present at the sprinkler or emitter inlet for it to perform as intended.
Manufacturers of sprinklers and emitters provide specifications for each of their products. these specifications typically have a table that lists the operating pressure, the flow the sprinkler will use, and how far the water will spray at that pressure. You will need to obtain these specifications for each of the sprinklers you intend to use. This information may be printed on a label attached to the sprinkler, or on the sprinkler packaging. Most manufacturers also make these specifications available on their web sites. Typically for a sprinkler this specification will list an inlet pressure as pounds per square inch (PSI) and then give a watering radius (feet) and flow rate in gallons per minute (GPM) that will occur at that pressure. A typical table might look like this:
|Pressure PSI||Radius Ft||Flow GPM|
The table above is a sample only, please do not assume these values shown are “typical”. In this sample we can see that at 20 PSI this sprinkler will have a radius of 10 feet and it will consume 2.10 GPM or water flow. Or at 30 PSI this sprinkler will have a radius of 12 feet and it will consume 2.60 GPM or water flow. As you can see a higher water pressure results in a larger radius and higher flow requirement, this relationship between pressure, radius and flow is true of most sprinklers. This is why it is so important to calculate what the water pressure will be when designing. If you design your sprinkler system with the sprinklers 12′ apart you, you would need 30 PSI of pressure at the sprinkler head so that it would spray the required 12′. You would be in big trouble if the pressure lost in pipes and valves resulted in the pressure at the sprinkler only being 20 PSI. You would get a dry area between the sprinklers. This is why it is so important for you to actually go through this whole tutorial and do the design right. (No that spacing is not an error, if the sprinkler radius is 12 feet, then you space the sprinklers 12 feet apart, not 24 feet. More on this later in the tutorial when we discuss sprinkler spacings and placement.) Don’t try to guess or assume “it will work.” I hear from tons of people wanting to know how to fix a system that they just threw together, and now it installed and there are dry spots all over the place. Unfortunately it almost always is very expensive to fix at that point, costing them far more than it would have if they had taken the time to learn how to do it right the first time.
For an emitter the product specification tables would include only operating pressures (PSI) and a flow rate in gallons per hour (GPH) for each of those pressures. (Radius of throw isn’t applicable to drip emitters.)
Can’t find a performance chart or specification for the sprinkler or emitter? Then I would suggest you find another brand and model. Not providing this vital information is an sign of lack of professionalism on the part of the manufacturer. My experience is that most products sold retail without specifications are poor quality “knock off” products, often made by a “copy cat” production plant that makes knock offs of anything they can find with expired patents that will fit into their molding machines. This week they make sprinklers, next week it will be cd cases. They often cut corners like using poor quality raw materials, reducing the amount of plastic in the body and using low quality molds. They are then sold in bulk cheap with no support or guarantee.
Pressure Requirements for Sprinklers
Spray Type Sprinklers, Rotary Nozzles, and Rotators:
For spray type sprinklers, rotary nozzles, and rotators most designers use an operating pressure of 30 PSI, unless a lack of available pressure forces a lower level. The vast majority of spray type heads and rotary nozzles/rotators are designed to operate most efficiently at 30 PSI. Remember that if you use a lower pressure the sprinklers will need to be spaced closer together, because the water won’t spray as far. Check the manufacturer’s performance chart for the sprinkler. Additionally, almost all spray type heads have a radius adjustment screw that allows you to reduce the watering radius for using the sprinkler in smaller areas. (When you adjust the radius using the adjustment screw on a spray head, you are actually reducing the pressure at the nozzle by means of a small valve inside the nozzle. As the pressure is reduced the water doesn’t throw as far, it’s exactly the same as shown on that performance chart, a lower pressure gives less radius.) At pressures above 45 PSI most spray heads start to create lots of mist, which results in poor sprinkler performance. This can also be controlled by using the radius adjustment feature to reduce the pressure. If all the heads are misting a better solution is to throttle the sprinkler zone control valve (cheapest solution) which will reduce the pressure at all the sprinklers on the valve circuit. A better solution is to install a pressure regulator on the mainline to reduce the pressure in the whole sprinkler system, or use special pressure regulating sprinkler heads or nozzles made by some sprinkler manufacturers. Use of these pressure regulators gives more accurate pressures than adjusting a nozzle or throttling a valve, thus they increase the sprinkler system’s efficiency. But they cost a lot more than throttling a valve. If you have a water source with reasonably steady pressure, like most municipal water systems, throttling a valve or adjusting a nozzle will be “good enough” for most people.
Rotor Type Sprinklers:
For rotor type sprinklers the higher the operating pressure the better, within reasonable limits. We don’t want to blow the sprinkler apart with high pressure– and rotors can cause mist too under extreme pressures. As a general rule, most rotor type sprinklers do not work well with less than 30 PSI operating pressure. The optimal pressure is easy to determine for rotors using the following rule, keep reading!
“Stryker’s Rotor Spacing Rule” states that the spacing in feet between rotor-type sprinklers can’t exceed the pressure in PSI at the rotor. So what that means is that if you want to put the rotors 35 feet apart, you rotor will need to operate at 35 PSI or higher, pressure. I like to aim for at least 5 PSI higher than the minimum, so for that 35′ spacing I would aim for 40 PSI.
Important! There is a lot of competition in the sprinkler business to see who can get the greatest radius from a rotor-type sprinkler. Manufacturer’s literature and packaging tends to wildly exaggerate the maximum spacing of rotors. They get those distances by testing the rotors inside a big building with no wind. Even the most gentle breeze will shorten the real-world watering radius (water droplets are very light). If the package says the rotor has a radius of 35 feet at 30 PSI– that all wonderful, but don’t try to install those rotors 35′ apart! In the real world you will not get that distance (unless you are watering inside a building.) If you have 30 PSI do not space the rotors more than 30 feet apart. If you ignore this rule, 9 chances out of 10, you will have dry spots in your lawn! (Yep, over-size ego alert, the rule is named after me. I came up with this rule many, many years ago. So it got my name. That’s how it works!)
Rotor Spacing Example: If you want to space the rotors 30 feet apart then you will need to use a pressure of at least 30 PSI for the rotor. If you want to space rotors 40′ apart you will need 40 PSI for the sprinkler head pressure.
Maximum Rotor Spacing: I don’t recommend spacing sprinklers farther than 55 feet apart unless you have an experienced professional design the sprinkler system. Many tricky problems occur with sprinklers when they are spaced greater than 55 feet apart. Remember that cost is consistent regardless of spacing so it will not save you money. bigger sprinklers cost a lot more money as well as the larger pipe, plus you almost always need a booster pump to get enough water pressure, so you have pumping costs (pumps are expensive to buy, maintain, and operate.)
Most emitters operate best at around 20 PSI. Some emitters are “pressure compensating” which means they should put out approximately the same amount of water over a wide range of inlet pressures. (I’ve found that many pressure compensating emitters are not a whole lot more “pressure compensating” than standard emitters are. Keep in mind that at pressures over 45 PSI emitters may blow apart. Barbed emitters installed in poly tubing may pop out of the tubing at pressures over 30 PSI.
Mix and Match:
Sometimes you need to use sprinklers that require high pressure such as rotors, with sprinklers that use low pressure on the same irrigation system. To do this the system is designed using the pressure requirements of the high pressure sprinklers. The low pressure sprinklers (or emitters) are installed so that a separate valve turns them on and off, and a special pressure reducing valve is used. These valves have a built-in pressure regulation device that reduces the pressure down to the correct amount for the lower pressure sprinklers or drip emitters. Almost all irrigation manufacturer’s now make pressure reducing valves, although you may have to go to a specialty irrigation store to buy them.
If you are working through the Sprinkler Design Tutorial, enter the sprinkler head operating pressure (or the drip emitter pressure if no sprinklers) on the “Sprinkler Heads” line of the Pressure Loss Table.
Remember- the pressure you enter in your table is the pressure for a single sprinkler head. So if you will have 10 sprinklers and they each require 30 PSI you still only write “30 PSI” on your pressure loss table. Also the value you enter should be the highest sprinkler head pressure requirement. So if you plan to use a spray head that will need 20 PSI and also a rotor that will need 35 PSI, you will enter the higher value- which in this case would be 35 PSI. Finally, remember why pencils have erasers. You can always come back and change this value later if you want to! So don’t agonize over it.
A lot of people ask me why you only write down the pressure for a single sprinkler. This is a bit difficult to understand but I will try to explain. I think the easiest way to understand is with a mental image. Think of the water moving through your sprinkler system as millions of water droplets, rather than a single mass of water. On it’s journey through your sprinkler system a single drop of water will loose pressure along the way. Each place where it will lose pressure is one of the items that is listed on your pressure loss table.
Let’s follow a drop of water through a typical sprinkler system! First our water droplet will travel through a pipe from the water company to your water meter. Then it will proceed through the meter into the house supply pipe and on to the irrigation system connection. From there our drop goes into the irrigation system and may pass through a backflow preventer. Onward it travels to the sprinkler zone control valve and through that valve into the lateral pipes leading to the sprinkler heads. Finally the drop goes into one of the sprinkler heads and is propelled out onto the lawn. Note that our droplet only passes through one sprinkler head on the way to the lawn. I’ll bet you’ve never seen water on the lawn jumping back into the sprinkler head so it can go back and try going out through another sprinkler! So it only passes through one sprinkler head. Awwwwwww!!! Starting to make sense, right? Thus we only consider the pressure needed for a single sprinkler head. (O.K. wise guy, yes I have seen water sucked back into a sprinkler head. But that’s not supposed to happen, it means something is wrong with the sprinkler system.) At any rate, even if you still don’t understand why you use the pressure loss for only a single sprinkler, please trust me, it’s correct! I’ve been doing this sprinkler design stuff for over 35 years and have designed thousands of systems. Plus this tutorial has been around since 1997 and successfully used by thousands of people. Plus it is used by dozens of colleges as an irrigation design text.
Still have some questions about sprinklers? Much more information on sprinkler selection is coming later in the tutorial, such as detailed information on the spacing to use between sprinklers and nozzle selection. If you want to jump ahead and check it out, click here. Just don’t forget to use your “back” button to return here!
Bubblers are generally used to flood small areas of the landscape with water. In most cases they are not suitable for lawn irrigation and are used for watering shrubs or sometimes groundcovers. They are most often used to water smaller areas where sprinklers would overspray water out of the area, although there are other specialty uses for them. For example I often use near floor to ceiling windows where I don’t want water spray to drift onto the windows. Bubblers generally need to be in level areas, since they flood water over the ground surface.
Some sprinkler manufacturers make “bubbler nozzles” that fit onto their standard spray-type shrub style or pop-up sprinkler bodies. The classic bubbler is simply screwed directly onto the end of a 1/2″ pipe.
Bubblers and drip emitters: The difference between a bubbler and a drip emitter is flow rate. Drip emitters flow at very low rates, most often 4 gallons per hour (16 liters/hour*) or less. The intent of a drip emitter is that the water would soak into the ground at the emitter location with a minimum amount of water puddling around the emitter. Bubblers flow at higher rates, often measured in gallons per minute rather than hour, and the intent of a bubbler is to flood the ground surface with water.
(*A little optional puzzle for you. Q. If you do the math 4 gallons rounds to 15 liters, so why did I say 16? A. Emitters aren’t designed in English units, they are actually metric. They are designed using liters, so in reality it is a 16 l/h emitter, not a 4 gph emitter. 16 liters rounds to 4 gallons, while 4 gallons rounds to 15 liters. It’s a rounding error issue caused by the unit values rather than bad math. OK, enough fun for the geeks.)
Combining bubblers with sprinklers: Normally bubblers are separated onto a valve circuit of their own so that the watering time can be fine-tuned for exactly how long it takes to flood the desired areas with water. However, a small number of bubblers with adjustable flows can usually be installed on the same valve zone with spray-type sprinklers that are watering adjacent shrubs or groundcovers. Installing bubblers on the same zone wtih spray -type sprinklers is not the most efficient way to go, but as long as it is only 2 or 3 bubblers and they are watering a very small area (not more than 3′ square per bubbler) you can generally play with the bubbler’s flow adjustments and get a reasonably workable watering balance. When watering a larger area using many bubblers or when using non-adjustable flow bubblers you should place the bubblers on a separate valve zone/circuit consisting only of bubblers. Placing bubblers on the same valve zone with rotors or drip irrigation seldom works out well. Do not combine bubblers on the same zone with lawn sprinklers.
There are a number of different types of bubblers available, so let’s start by attempting to group them into some loose categories.
Flood bubblers do just what the name implies, they flood the area around them with water. They further divide into two types, adjustable and non-adjustable.
The adjustable flood bubblers are by far the most common type found, and are what most people think of if they are familiar with bubblers. An adjustable flood bubbler is essentially just a small water valve. It typically has a screw or knob that is used to adjust how much water flows out of it. Most bubblers are designed so that the water gently “bubbles” out of them, the reason being to avoid erosion caused by a strong stream of water. The amount of area they will water is very hard to predict, it depends on how far open the valve is (how much water is coming out), how long it is left on, and the soil type. For purposes of planning your irrigation system, I have found that in most situations flood bubblers will water an area about 3 feet in radius, at a flow of 2 GPM. Understand that this would be a circular 3′ radius area, so if you put them 6′ feet apart that would give you 6′ diameter wet circles that just barely touch each other! In practice if I am watering a long planter strip 3′ wide with shrubs in it I will install flood bubblers 3′ to 4′ apart down the length of the planter. If the area is wider than 3′ I will install a second row of bubblers. Again, bubblers tend to be very hard to predict, you may find you can water a much wider area with a single row, or if you have sandy soil you may have difficulty getting the area flooded with them 3′ apart!
Non-adjustable flood bubblers are just that, non-adjustable. Water flows out of them at a fixed rate. The flow rate depends on the manufacturer, common flows are 1/4 GPM, 1/2 GPM, 1 GPM, and 2 GPM. They are a bit harder to determine spacing for, but that is solved by the intended use. Typically you install one fixed flow bubbler at each shrub or if they are very small shrubs (not more than 18″ – 24″ diameter full grown) you might install 1 non-adjustable bubbler between two shrubs to water both of them. Once again the area watered is very variable depending on which flow rate you choose,how long you run the bubbler, and the soil type. Other than having a non-adjustable flow they are very similar to the adjustable flood bubbler.
A trick you can use is to go to the store and purchase a flood bubbler to use as a test. Also purchase the adapters needed to attach it to the end of a garden hose, it will probably be an odd “Rube Goldbergian” type assortment of adapters and nipples. Install the bubbler on the end of a garden hose, turn it on, adjust the flow, and see how large an area it will flood with water in your yard. To determine the flow you are using for your design, you can measure the flow by using a 1 gallon bucket and seeing how long it takes the bubbler to fill it. 15 seconds to fill is 4 GPM, 22 seconds is 3 GPM, 30 seconds is 2 GPM, 60 seconds is 1 GPM, etc.
Stream bubblers spray a narrow stream of water, most often the stream shoots out 2 to 5 feet from the bubbler. The purpose of stream bubblers is to get the water out away from the bubbler and thus allow watering a larger area with it. In actual practice my experience is that they don’t do a good job of actually flooding a large area. However they are great for watering a group of plants provided the plants are located in the immediate vicinity of where the stream lands. So study the spray pattern of the streams and examine whether the streams will reach the plants you want to water. For example, for large hedges I often will use a stream bubbler that has two opposing streams, one in one direction and a second in the other (called a “center strip” pattern.) I can center one of these between two plants that are 3 to 6′ apart and water both plants with a single bubbler. This is great for large hedges and limited budgets. Keep in mind that foliage will block the spray from a stream bubbler so you may need to trim the plants to keep them out of the bubbler’s spray trajectory. As with other bubblers the area watered by stream bubblers needs to be reasonably level so the water puddles up and doesn’t run off.
I have used lots of stream bubblers on commercial projects where drip irrigating shrubs is impractical due to the high maintenance of most drip systems. These are typically new landscapes where I am designing both the landscape planting and the irrigation system. In this situation I lay out the irrigation system with stream bubblers 36″ apart with the streams adjusted to spray 12″‘. Then I plant the plants at the end of the streams around the bubblers. A full circle stream bubbler typically has 6 streams of water allowing it to water 6 small plants, like daylilies, that are grouped around it. Note that my experience is that this idea doesn’t work as well with larger plants and/or plants placed further than 24″ away from the stream bubbler. If I need additional rows of bubblers I put the rows 24″ apart forming a triangle pattern with the bubblers. Because these are commercial projects where I typically use this stream bubbler layout, I usually use stream bubbler nozzles and install them on 6″ pop-up bodies so they drop to ground level when not running. It looks nicer and it is much safer.
Micro-bubblers are lower flow bubblers often sold as adjustable flow drip emitters. They often have barbs so that they may be installed on poly drip tubing. They are called bubblers because they typically have flows over 4 gallons per hour, which is a higher flow than most soils can absorb without the water pooling on the surface. Although they are adjustable flow, micro-bubbler flows are too low to be compatible with spray or rotor type sprinklers, so don’t put them on the same valve circuit. For more on micro-bubblers see the drip irrigation guidelines tutorial, where they are called adjustable flow emitters.
This article is part of the Sprinkler Design Tutorial Series
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