Residential Irrigation (Continued)
There are many types of irrigation equipment available today. They include but are not limited to sprinklers, spray heads, spray stakes, misters, and drip lines. Some products have multiple names. This is by no means an exhaustive list of types of irrigation equipment, but it covers the most common.
Types of Sprinklers
Sprinklers are the most common type of irrigation equipment. They have evolved over the years, so there are many kinds of sprinklers.
The yard sprinkler created 1932 by a citrus farmer is the most common piece of irrigation equipment. The first impact sprinklers were mounted atop metal pipes. These raised sprinklers are still used today to water a lot of vegetable gardens and landscape beds as well as for frost prevention for orchards and fruits.
Impact sprinklers are typically made of brass or plastic. They are so named because they use the force of the water exiting the nozzle to swing an arm around to make “impact” with the sprinkler frame. This impact causes the sprinkler to rotate slightly. This motion happens repeatedly so that the sprinkler rotates providing coverage of a large area and results in the common “cha-cha-cha” sound as it rotates.
Because of the inconvenience of mowing around the impact sprinklers mounted on pipes, the pop-up impact sprinkler was invented. The same type of sprinkler was enclosed in a cast iron or plastic case 4-6 inches in diameter with a lid on top of the sprinkler head. The enclosed sprinkler case could then be placed in the ground. When water pressure was applied to the sprinkler, it would rise out of the case about 4 inches above the soil surface and spray the surrounding area. When the water was turned off, a spring inside the case would force the sprinkler head and lid back down into the case so it no longer extended above the ground.
These pop-up impact sprinklers had issues as well. A particular brand of high-vacuum mowers would occasionally suck the sprinkler head up out of its casing enough to chop it off. In certain landscapes, sand and dirt would also get into the casing preventing the sprinkler from retracting leaving it in an extended position. This led to more improvements.
Rotor and Gear Driven Sprinklers
To overcome the problems experienced with pop-up impact sprinklers, manufacturers tried to find a solution that eliminated the need for the large cavity inside the pop-up impact sprinklers. The new design to fix this used an internal drive mechanism.
Rotor and gear driven sprinklers look and work very much the same. While they both have different internal drive mechanisms, they do both depend on a flow of water moving past some internal part of the sprinkler. When water pressure is applied, a 1-inch or so diameter shaft extends about 4 inches above the ground. As water flows past the internal drive mechanism, it causes part of the extended shaft to rotate. The shaft is sealed to prevent sand and dirt from entering the sprinkler which helps to eliminate many of the problems with the previous generation of pop-up impact sprinklers. This also made the tops of the sprinklers virtually impossible to see when retracted.
Stream rotors utilize rotor and gear driven technology but are different from previously mentioned types of sprinklers (impact, gear driven, and rotor). The area covered by a stream rotor is typically somewhat smaller than the others. Unlike the previous types of sprinklers which emitted a single stream of water, stream rotors emit multiple streams (usually 6 or more) simultaneously. While stream rotors will not replace the larger rotor or gear driven sprinklers, the smaller diameter of their throw makes the ideal for smaller turf areas.
Spray heads get their name because they spray water over an area rather than emitting a stream of water. The type of nozzle used on the spray head determines its pattern of irrigation. When purchasing spray heads, you can choose from heads with a variety of patterns such as full circle, half circle, third circle, quarter circle, and more. You can also buy adjustable arc nozzles. You can even choose rectangular pattern nozzles. Different size nozzles yield different size diameters of throw such as 16, 20, 24, or 30 feet. You can also buy nozzles with different pop-up heights from 2 inches to 12 inches. These heads are usually used in landscape beds or areas too small for sprinklers and stream rotors.
Drip irrigation is different from irrigation using sprinklers and spray heads. The latter apply water over an entire coverage area while drip irrigation applies water only to the root zone area. Drip irrigation allows you to apply water to plants without applying it to surrounding areas which may not require water. It also allows you to irrigate any time of day since the foliage of the plant never gets wet virtually eliminating the chance for disease. Because water is applied directly to the ground, such systems are very efficient.
Drip emitters allow you to regulate the amount of water that is “emitted” from an irrigation line. They are designed such that they emit water at a relatively steady flow rate regardless of pressure.
If a pipe has holes drilled in at some regular interval such as every foot, then when water is supplied to one end of the pipe, the water emitted through the hole closest to the water source will emit some amount of water. Each subsequent hole in the pipe would emit slightly less water as the pressure will be less the farther you get from the water source. If, however, you placed emitters at each hole along the pipe, all the drip emitters would emit roughly the same amount of water.
Drip emitters come in different shapes, sizes, and colors. Some of the common flow rates are 0.5 gallons (or two liters) per hour, 1 gallon (or 4 liters) per hour, and 2 gallons (or 8 liters) per hour. Emitters with all three flow rates can be placed on the same section of drip tubing, and each will emit the amount of water corresponding to their flow rate. How the emitter flow rates are labeled depends on whether they are sold in the US (gallons) or overseas (liters). Some emitters have multiple outlet emitters to which you can attach 5 or 6 pieces of ¼ inch spaghetti tubing to provide water to several plants or pots.
Drip tubing can range in diameter from ¼ inch up to 1.5 inches or more in a variety of styles and is always black. It can be purchased in 100-, 500-, or 1000-foot rolls. Common drip tubing diameters include 3/8-inch (10 mm or “380” size), 1/2-inch (13 mm or “500” size), 5/8-inch (16 mm outside or “600” size), and 5/8-inch (16 mm inside or “630” size). The 5/8-inch tubing (sizes “600” and “630”) are most popular. Because it is made to be resistant to sunlight, drip tubing can last 30+ years in the sun.
There are all types of fittings that can be attached to the drip tubing, but the size of the fitting must match that of the tubing. There are “T”s, elbows, and adaptors to connect to male or female garden hose threads to name a few. The open end of the tubing should be plugged with a figure 8 clamp.
Driplines in 1000+ foot rolls that are made of “600” size drip tubing with emitters pre-installed every 12, 18, or 24 inches can be purchased. The emitters are evenly spaced, so they are a great option if you plan to irrigate a bed with a 2x2 grid of emitters or in an orchard or area with evenly spaced plants. However, if the plants to be watered by the drip tubing and emitters are not evenly spaced, then you are better off purchasing drip tubing and emitters so that you can better space the emitters to match your planting pattern.
Microsprinklers and Microsprayers
Microsprinklers and microsprayers are miniature plastic sprinklers and sprayers that are usually mounted atop some type of plastic stake. They are connected to one end of a length of spaghetti tubing which is connected to drip tubing on the other end. These are hybrids of drip irrigation and sprinkler irrigation technology making them more efficient than sprinklers but still less efficient than drip emitters.
Microsprinklers can have flow rates of 5-60 gallons per hour, sometimes more. They are used a lot in greenhouses and orchards. They are also useful in landscapes with coarse, sandy soils. Drip emitters are not good in such environments because the soil drains so well that the water from the emitter drains vertically and there is very little lateral movement of the water away from the emitter. This limits coverage in the root zone. Because microsprinklers spray water over a much larger area, they are more effective irrigating a much larger root area. Microsprinklers are used extensively in citrus groves where the soil is sandy.
In areas where the soil is predominantly loamy or clay, the vertical drainage is much slower and lateral water movement from the drip emitter are often 2 or more feet (as opposed to 4-6 inches in sandy soil). In landscapes with loam or clay soils, a drip emitter is quite effective and microsprinklers are not typically used.
Spray stakes are a special type of microsprayer used with potted plants. Like sandy soil, potting soil is typically porous and drains vertically with little lateral movement of water. For this reason, drip emitters are often not effective as only a small portion of the root section will receive water.
Spray stakes are placed on the side of the pot. They are attached to one end of spaghetti tubing while the other end is attached to drip tubing. When water is applied, the microsprayer on the spray stake sprays water in a pattern that covers the entire surface of the potting media so that the entire root system receives water.
Filters for a Drip System
There is usually no need to filter irrigation water used with sprinkler systems since their large nozzles can pass soil particles or sediment in the water without clogging the sprinkler head. But emitters, microsprinklers, and microsprayers have tiny outlets which can easily become clogged by soil particles. For this reason, you should always filter water provided to a drip system.
The filter used on a drip system should be a 150-mesh filter (i.e. there should be at least 150 holes in a row per inch of the filter). Some emitters, microsprinklers, and microsprayers require a 200-mesh filter. Refer to the manufacturer instructions and purchase filters with the correct mesh rating.
There are two problems that you should be aware of when using filter systems. If you are using pond water or surface water as a source for your drip system, it contains lots of sediment and organic matter which can easily clog a filter screen. So typically, the filter will have some type of self-cleaning screen filter. This type of water also has algae in it which may collect and grow on the filter screen. There are filter systems that include chlorine injecting mechanisms to inject small but continuous amounts of chlorine into the water to prevent algae problems. But it is likely cheaper to simply use well or municipal water for your drip systems.
The second problem for drip systems occurs when using well water which often has a lot of iron in it. While the iron is in liquid form, it will flow through the drip irrigation system just fine. But when it exits the emitter or microsprayer and contacts air, it will oxidize forming solid iron oxide deposits which will quickly plug the small openings in the tips of drip emitters and microsprayers. If you notice reddish-brown stains in your sinks or tubs, then your well water should be tested for iron. If the iron content is determined to be 0.3 parts per million or more, then this will be problematic.
Pressure regulators are used to protect drip irrigation systems because they do not require as much pressure as sprinklers to operate correctly. In fact, too much pressure can cause the emitters to pop out of the tubing. For example, drip systems work great at around 30 pounds per square inch (PSI) of water pressure, but at 40 PSI the emitters can start popping out of the tubing. For most landscape drip systems, a 30 PSI pressure regulator will work great. There is no need for the expensive brass regulators as the simple, plastic ones work just as well and are significantly cheaper.
Timers and Controllers
To irrigate a landscape, one must first know when to irrigate, how much water to apply, and how long the irrigation system must operate to apply that much water. Most landscapes will be divided into zones, and each individual zone will typically contain several sprinklers, sprayers, or drip equipment all the same type. Since different zones can each have different equipment possibly with different flow rates, some zones require different watering durations than others. While one could operate each zone manually, it is simply a better use of time to automate the process.
This automation was originally accomplished using timers. Manual valves were replaced with electric valves and wired to an irrigation timer allowing you to configure the timer with the times each zone should run.
The first timers where electromechanical devices with a clock motor running everything. You could set the day of week and current time, the day and time when the irrigation system should start running, and how long each zone should irrigate. While these timers worked, they had some limitations. The day and time when the irrigation system was a global setting which controlled all zones. One zone could not be set to start on a different day and/or time as another. Even though you could set how long each zone was to run independent of other zones, one zone could not be set to run for 20 minutes one day and 30 minutes a different day. Also, the maximum amount of time you could set a zone to run for was 60 minutes which is often not enough for drip zones.
The second generation of timers was an electronic timer with an LED readout. These timers were much more flexible than the first as they allowed you to setup three programs (A, B, and C). Each program could be assigned to run on different days. Any combination of zones could be assigned to one or more programs. This was a vast improvement over the electromechanical timers as it provided much more flexibility. Though much more complex to program than electromechanical timers, these electronic timers were prone to being damaged by power surges such as might occur from a lightning strike during a thunderstorm.
The most recent advancement in timers is a hybrid of the previous two combining the use of use of electromechanical dials and buttons with an electronic timer. These have a combination of push buttons, dials, and an LED all used to program the system.
While the above advancements in timers and controllers have made irrigation systems much more automated, there is still one inherent issue with using such devices. The amount of water needed by a landscape changes with temperature and humidity. Settings that work well in the spring and fall may not provide enough water during the heat of summer months. For this reason, some hybrid timers now have a “water budget” feature that defaults to 100%. Once programmed, the timer/control will irrigate the zones 100% of the time for which they were programmed to run. But in the heat of summer, you can simply change the single water budget setting to, say, 125%, and when the irrigation system runs going forward, it will extend the time each zone runs by 25%. This feature saves the user from having to reprogram every zone on every program (A, B, and C) to run longer in summer.
Irrigation valves typically fall into one of three categories: ball valves, gate valves, and electronic valves. Ball valves and gate valves are manually operated and are fine if you are not going to automate your irrigation system. Ball valves have a ball inside with a hole through it. When the hole is aligned with the pipes on either side of the valve water can pass through. When the valve is turned 90°, the hole becomes perpendicular to the piping closing the valve. You should always open and close ball valves very slow so as not to cause a water hammer problem which can damage some systems. A gate valve is similar. It has a gate inside that is raised or lowered to open or close the valve when you turn a knob several times.
Electric valves are used with automatic timers. They contain a diaphragm that opens when 24 volts is applied to the valve’s solenoid and closes when the voltage is removed. There is also a way to manually open the valve for cases where there is no power, but if used, you will be required to also close it manually. These electrical systems pose no threat from electrocution as they carry about the same voltage as runs an electric train. When used, electric valves should always be enclosed in a valve box which is placed in the ground. The top of the valve box has a solid removable lid, is always installed at ground level, and is usually green to blend with the landscape. The sides are solid except they have holes to allow pipes to enter the box. There is no bottom to a valve box which allows them to drain should they collect water.
There are many types of piping used in irrigation systems. Some of them include PVC, CPVC, polyethylene, and galvanized iron. The two most used types are white PVC and “black roll pipe” made of polyethylene. In Southern regions, PVC is most common since there is little chance of the water in PVC pipes freezing if they are buried 12 inches deep as recommended. In Northern regions where extreme cold weather is the norm, “black roll pipe” is more common because it will expand some if the water inside freezes minimizing damage from freezing.
Swing Pipe or Funny Pipe
If a car runs over a sprinkler head that is attached directly to PVC piping, not only will the head get crushed but often the PVC pipe attached to the head will also get crushed. To deal with this, most manufacturers make available something called swing pipe or funny pipe that is much more flexible than PVC. About 2-4 feet of it is typically installed between the PVC and the sprinkler head providing flexibility in case the head is run over as well as allowing the installer to better position the sprinkler heads.
Anyone installing an irrigation system using city or county water will have a water meter for the water supplied to their home. In some areas, the municipality will allow you to pay for a second meter so that they can track your household water usage separate from your irrigation water usage. Should you decide to do this, you will be charged for the water for both but only for sewer for the household meter since your irrigation water should be absorbed into the soil and not return to the sewer system. Depending on the cost of the meter, this may or may not be advantageous to the homeowner.
Backflow prevention or anti-siphon devices are required by all municipalities to prevent water from the irrigation system from backing up into and contaminating the drinking water supply. The specific type of device that is required is dictated by the municipal water system. The double check valve is the most common device used for this purpose providing two check valves in a series so that if one fails, then the other will still operate preventing backflow and possible contamination. All such devices have test ports on them so that they can be tested. Municipalities usually require that they be tested periodically such as yearly.
Using Wells for Irrigation
If a home has a well, it is possible to utilize it for irrigation if the well has a flow rate of 15 gallons per minute (GPM) or more. Most well drillers, however, install 5 GPM pumps regardless of the well’s flow rate, so you may need to upgrade your well pump from a 5 GPM pump to a 15, 20, or more GPM pump to use it for irrigation. If you do upgrade the well pump to one with a higher flow rate, you will also be required to upgrade your pressure tank to match in order to prevent damage to the pump from starting too often.