- - AGRICULTURE CORE CURRICULUM - - (CLF6000) Advanced Core Cluster: ORNAMENTAL HORTICULTURE (CLF6700) Unit Title: LANDSCAPE DESIGN, CONSTRUCTION, AND MAINTENANCE ____________________________________________________________________________ (CLF6704) Topic: IRRIGATION DESIGN AND Time Year(s) INSTALLATION 4 hours 3 / 4 ____________________________________________________________________________ Topic Objectives: Upon completion of this lesson, the student will be able to: - Cite the requirements for design, installation and maintenance of irrigation systems. - Demonstrate an understanding of the requirements and uses of irrigation systems as they relate to the following: Learning Outcome #: (M-2) - Prepare a simple landscape design. (M-4) - Design a turf and shrub sprinkling system for an area specified by the instructor. Special Materials and Equipment: Drawing vellum with 1/4" grid, drawing supplies, tape measures, architect's scales, and a rod and level; flow gauge; an assortment of sprinkler irrigation pipe, sprinkler heads, fittings, PVC cement, primer, and assembly tools; an assortment of drip irrigation tubing, emitters, fittings, and drip assembly tools. References: Cotton, Lin. (1985). ALL ABOUT LANDSCAPING. Available from: Ortho Books, P.O. Box 5047, San Ramon, CA 94583. Hannebaum, Leroy. (1981). LANDSCAPE DESIGN: A PRACTICAL APPROACH. Reston, VA: Reston Publishing Company. Ingels, Jack E. (1987). LANDSCAPING (3rd ed.). Albany, NY: Delmar Publishers. Landphair, H. C., & Klatt, F., Jr. (1979). LANDSCAPE ARCHITECTURE CONSTRUCTION. New York: Elsevier Science Publishing Company. Editors of Sunset Books and Sunset Magazine. (1984). LANDSCAPING ILLUSTRATED. Menlo Park, CA: Lane Publishing Co. Editors of Sunset Books and Sunset Magazine. (1989). WATERWISE GARDENING. Menlo Park, CA: Lane Publishing Co. Editors of Sunset Books and Sunset Magazine. (1988). WESTERN GARDEN BOOK. Menlo Park, CA: Lane Publishing Co. Wilson, Scott. (1976). LANDSCAPE CONSTRUCTION MANUAL. San Luis Obispo, CA: California Polytechnic State University, Vocational Education Productions. Evaluation: Unit Exam ===================================================================== *** INSTRUCTORS PLEASE NOTE *** The detail of this topic presentation goes beyond the scope necessary to meet the requirements of the Core Cluster in this area. It will take longer to teach than indicated above if covered entirely. It is included for local enrichment as appropriate to the class. ===================================================================== TOPIC PRESENTATION: IRRIGATION DESIGN AND INSTALLATION ===================================================================== INSTRUCTORS' NOTE This topic presentation is divided into three main parts covering the planning of irrigation systems, sprinkler systems, and drip systems. Additional information on irrigation can be found in units (CLF6450) Irrigation and Drainage, and (CLF7400) Irrigation. ===================================================================== PART I: PLANNING IRRIGATION SYSTEMS A. Irrigating Ornamentals in the Landscape: 1. The Importance of Irrigation Systems: Irrigation systems are essential in a modern landscape. a. In the 1990s, landscape plantings are an integral part of nearly all residential, commercial, and public construction. b. The value of ornamental plantings is widely accepted, and substantial investment is made in beautifying the environment with plants. c. The most immediate need of these plants is water. d. Well-designed, properly installed, and well-maintained irrigation systems are critical if investment in the landscape is to be protected. 2. Methods: Many innovations have been developed for irrigating the landscape. a. Landscape conditions vary tremendously and demand different approaches to irrigation. There is a complex variety of equipment and technology to control water delivery, and meet these demands. b. To simplify, though, most irrigation systems can be classified as either sprinkler irrigation or drip irrigation. 1) Sprinkler systems are used mainly for turf and ground covers. Pop-up spray heads, streamers, bubblers, mist nozzles, and shrub heads are all types of equipment found in sprinkler systems. 2) Drip systems are used mainly for irrigating trees, shrubs, and container plantings, but can be adapted for a variety of applications. Drip equipment includes mini-sprinklers, soaker-tubing, and drip emitters. B. Defining Irrigation and Drainage: 1. Irrigation is applying water other than natural precipitation to the soil. 2. Drainage is the removal of excess gravitational water from the soil by natural or artificial means. For further information on drainage systems, refer to (CLF6952) Irrigation and Drainage. C. Planning an Irrigation System: There are a number of factors to consider when planning and designing an irrigation system. 1. System installation must be scheduled carefully. a. Drainage and irrigation both involve a lot of underground work, and are more easily installed before plants, hardscape elements, and other surface features are put in place. b. At the same time, accurate placement of sprinkler heads and other parts of the system requires that certain grading and construction features be complete before irrigation work begins. 2. An accurate scale drawing of the area to be irrigated should be laid out, so that a plan can be developed. a. 1" = 4' and 1" = 8' are is a standard scales to use for most residential and small commercial sites. b. Measurements should include significant changes in elevation in addition to the location of buildings, walkways, decks, patios, driveways, plants, and utility lines. c. Hose bibs or other access to water should be marked. __________________________________________________________ ACTIVITY: 1. Have students map out the area surrounding the classroom or an adjacent area of the school yard that might benefit from landscape irrigation. 2. Useful equipment includes tape measures, architect's scales, and a rod and level for determining angles and elevation differences. 3. Have students work in teams of three or four, taking turns at measuring and recording tasks. Each student should turn in their own map based on the group's measurements. __________________________________________________________ 3. Permits may be required for certain irrigation installations. a. The municipality or county should be consulted. b. This is a good time to check on code requirements regarding such things as backflow-prevention devices, types of pipe which can be used, and burial depth for pressurized water lines. 4. Information on available irrigation equipment should be gathered. a. Catalogs from various manufacturers supply technical data which allow calculations such as sprinkler head spacing and flow requirements to run the system. b. Using one manufacturer's equipment on a site, rather than using a mixture of equipment, makes installation and system maintenance a simpler task. __________________________________________________________ ACTIVITY: 1. Obtain manufacturers' literature describing complete lines of irrigation products. 2. Have students work in groups to select, from the product catalogs, equipment which would be appropriate for irrigating the areas mapped in the above activity. __________________________________________________________ 5. Existing and proposed conditions of the site should be analyzed. a. Location and size of existing and proposed hose bibs should be determined. b. The water source should be checked. 1) The available pressure (in pounds per square inch) and flow (in gallons per minute) should be determined. 2) Find out if there are any problems with water quality such as rust or silt or a high level of salts in the water supply. __________________________________________________________ ACTIVITY: 1. With a pressure gauge, have students determine the water pressure available at the hose bib nearest to the classroom or agriculture compound. Use a flow meter to check flow as well. 2. Check the pressure with the flow shut off (static pressure). Check the pressure with the flow running (dynamic pressure) at five gallons per minute, then for two gallons per minute. Compare the results. Determine how much flow there is (in gallons per minute) when the pressure shows about 30 psi (a common operating pressure for sprinklers). __________________________________________________________ c. Test soil texture and assess permeability. The rate at which water can infiltrate the soil is important in designing and running a sprinkler system. d. Note location and water demands of existing plants. Assess water demands of proposed vegetation. Will the garden be lush and jungle-like, or a water-conserving xeriscape? e. Analyze slopes and aspect. 1) The steepness of a grade will affect water infiltration and runoff. Steep slopes cannot be sprinkler-irrigated for long without causing runoff. (This is a good application of drip irrigation.) 2) How grades face in relation to the sun will affect the rates of evaporation and transpiration. Slopes facing north and east require less irrigation. f. Determine summer and winter shade patterns. These affect demand for water. g. Determine prevailing wind directions because wind can throw off irrigation patterns and create dry spots. This must be compensated for. h. Try to anticipate how growth in the landscape might interfere with irrigation lines or sprinkler spray patterns. Look ahead and design around these problems. i. Pay attention to traffic patterns. For example, don't place sprinkler heads where they are likely to trip someone or get broken by an automobile. 6. Plan and design for water conservation. For further information on water conservation in landscape irrigation, see topic plan (CLF6455) Conserving Water in Irrigation. 7. Try to anticipate any possible future needs. For example, if an adjacent area might be landscaped at a future date, design into your plan easy access to the water supply near that site. Some forethought in the present can save a lot of work in the future. 8. Irrigating Different Landscape Situations: Different parts of the landscape will require different types of irrigation. a. Turf: Lawn areas are the biggest users of water in the landscape. They require even, full coverage by sprinklers. b. Shrubs: They require water in their root zone only, and can be irrigated with drip irrigation, bubblers, or low-trajectory sprinklers. Obviously, sprinklers have limited throw around leafy shrubs, so this application for sprinklers is limited. c. Trees: Generally the deep root systems of trees require slow, deep irrigation. Drip, or bubblers with well-formed basins are appropriate here. d. Planter Boxes and Containers: Bubblers and drip lines serve these areas best. e. Ground Covers: Coverage required depends on the species used. Either sprinklers or drip can be used successfully. f. Sloped areas respond well to drip irrigation; erosion and runoff are reduced. PART II: SPRINKLER SYSTEMS A. Description of Sprinkler Irrigation: Sprinkler systems essentially create artificial rainfall on ornamental plantings. By the use of different nozzles and sprinkler heads, the rate of precipitation, as well as the duration, can be controlled. 1. Applications: Sprinklers can be used to irrigate just about any type of ornamental planting. a. The primary use of sprinklers is for a planted area which requires full, even coverage. The best example of this is turf. b. There is a wide variety of special nozzles to allow sprinkling areas of different sizes and shapes. c. Not all sprinklers "sprinkle": 1) "Bubbler" heads are used as part of sprinkler irrigation systems to flood planter boxes and other plantings in retained areas. 2) Mist nozzles can be used to humidify an area and wet down foliage, if this is desired. 2. Advantages of Sprinkler Systems: a. Correctly laid out, sprinklers provide full, even coverage of a landscaped area. This is particularly important with turf. b. Sprinklers can be used in uneven terrain. Level surfaces are not necessary as with flood and furrow irrigation techniques. c. Sprinkling cools and humidifies the microclimate of the irrigated area. This is preferable for many species of landscape plants. d. Sprinkling plants cleans off dust, and disrupts some pests such as mites. e. Buried sprinkler lines are relatively strong and subject to little damage if correctly installed. f. Sprinklers can be used for frost protection of ornamentals if necessary. (Refer to (CLF7552) Irrigating for further information on this topic.) B. General Principles of Sprinkler Systems: 1. Sprinkler systems operate at relatively high pressures (20-30 psi and higher). 2. Sprinkler systems require relatively high flow rates. An availability of less than 4 or 5 gallons per minute leads to expense and frustration in designing the average residential system. More water flow is needed for larger installations. 3. Sprinkler systems provide uniform areas such as turf with even precipitation rates and full coverage. a. Precipitation rate is the amount of water, in inches, a sprinkler puts on an area in a given amount of time. Other conditions equal, a nozzle with a large orifice will have a higher precipitation rate than a nozzle with a small orifice. b. A sprinkler with half the precipitation rate of another must be allowed to run twice as long to put the same amount of water onto the landscape. c. Overlapping spray patterns are required to achieve a uniform water application. d. To the greatest extent possible, irrigated areas should be overlapped equally to minimize wet and dry spots. These show up most easily on turf, the primary application of sprinkler systems. 4. Accurate design is critical with sprinkler systems. a. Relatively high pressure and flow requirements mean care must be taken not to design irrigation circuits that demand too much of the water supply. If this is the case, the equipment will not work. b. Once the system is in the ground it is time-consuming and expensive to make changes. Irrigation requirements must be accurately assessed at the design stage. 5. Varying the amount of water delivered can be controlled in several ways. For instance, areas requiring less water can have: a. Nozzles with lower precipitation rates. b. Less overlap in spray patterns. c. Less time that the sprinklers are turned on (run time). d. Less frequent irrigations. All of these options result in less TOTAL precipitation. C. Water Supply: As suggested above, the water supply for a sprinkler irrigation system is critical. Some requirements: 1. Adequate Flow: a. If supply lines are narrow or corroded, the gallons per minute that can flow into the system will not be enough to run more than a sprinkler or two at a time. b. Five gallons per minute is about MINIMUM for the average residential system. 2. Adequate Pressure: This is related to flow. Increased flow reduces available pressure. a. 20 pounds per square inch is about the lowest pressure that can be used for sprinkler systems. b. 30 psi at the operating flow rate is better for average equipment requirements. c. In a system using well water, a pump must be used to pressurize the irrigation system. 3. Adequate Water Quality: If water has high levels of sand, silt, or rust coming through at the source, filters must be used or the irrigation system will not function properly. Valves will jam and nozzles will clog. D. Components of a Sprinkler System: Described below are the basic components of the average sprinkler system. They are listed in the order they would be encountered as water flows through the system. For more detailed information on sprinkler system components, refer to topic plan (CLF6453) Sprinkler Irrigation Systems. 1. Controller: This unit controls the opening and closing of valves at pre-programmed times. There are a wide variety of controllers on the market now, with varying capabilities. Some of their features: a. Controllers have either built-in or external step-down transformers. They connect to standard 115 volt current and run on 24 volt current. The 24 volt output is safe to run into the field to control valves. b. As few as four or as many as 30 or more valves (or "stations") may be operated by one controller. Usually, only one station is turned on at one time. c. Controllers are either electro-mechanical or solid state in nature. Most modern units are solid state; they offer better dependability, more programming options, and lower cost. d. Some controllers are designed for indoor mounting; more expensive units can withstand outdoor conditions. Special enclosures are available to deter vandals. e. Controllers allow much versatility in irrigating the landscape. f. Multi-strand wire (24 volt) leads from the controller out to the various remote valves. 2. Point of Connection: Abbreviated "POC" on an blueprint or site plan, this is where water comes into the landscape area. It may be an existing hose bib or the water meter. 3. Gate Valve: Shuts off the water. a. A gate valve is a valve situated between the point of connection and the rest of the irrigation system. b. It usually remains wide open, but can be shut down in case repairs or additions have to be made to the system. c. Gate valves are not designed to be opened and closed on a regular basis, as a control valve is. 4. A screen and/or filter is installed near the beginning of the system to catch any foreign material coming through the water supply which might otherwise jam the valves or clog up sprinkler nozzles. 5. Backflow Prevention Device: This is a legally required part of any irrigation system in most communities. The backflow preventer keeps water which has entered the irrigation system from backing into the main water supply in the case of a pressure reduction in the supply. 6. Pressure Regulator: A pressure regulator adjusts downward the water pressure going into the irrigation system. It is not required for all systems. 7. Control Valves: Valves open and shut the flow of water from the point of connection to the sprinkler heads. 8. Pipe: Irrigation pipe is the "backbone" of any irrigation system. a. Polyvinyl chloride (PVC) is the primary pipe in use for irrigation systems today. b. Galvanized iron was once the most common material used for sprinkler systems. Presently, it is used only for above grade situations where extra strength and resistance to light are required. 9. PVC Fittings: PVC fittings all have the same inside diameter for any given size. They are used for a variety of purposes: a. Connecters to join pipe. b. Adapters to join differing sizes and types of pipe. c. Special fittings. 10. Sprinkler Heads: These represent the "end of the line" in an irrigation system, and determine how far and in what direction the water goes. There are a wide variety of sprinkler heads on the market to fit just about every irrigation situation. The main types are listed below: a. Spray Heads: These are used in small areas, and spray approximately eight to sixteen feet. b. Stream Spray Heads: These rotating heads put out less water at one time, and are designed to throw medium distances, from 10 to 30 feet. c. Impact Heads: These "rainbird" type heads rotate slowly with the impact of a spring-loaded hammer against the stream of water. They are used in large-scale plantings, set from 25 to 40 feet apart. d. The sprinkler heads described above are available in fixed or pop-up models. 1) Fixed heads are mounted above grade. 2) Pop-up heads are installed below grade, and are designed to pop up when the system is pressurized. e. Bubblers: These are a special type of nozzle used to allow a high volume of water to spill out onto the soil in all directions. They are used in planter boxes and for other plantings that have some kind of retainer around them. f. Mist Nozzles: These are for special applications where atomized droplets are desired for humidifying an area. 11. Moisture Sensors: These can be placed in the soil and connected to the controller (either by a wire or by radio communication) to indicate when soil moisture levels are high or low. E. Basic Principles of System Design: While it takes considerable knowledge and experience to design efficient sprinkler systems, some major principles can be listed that will help guide the designer to success: 1. Sprinkler systems are divided up into circuits. a. Each circuit is controlled by one valve. b. Only one circuit is operated at a time. c. Sprinkler heads on each circuit should be rated to use no more than about 75% of the available flow when they are all added together. For example, if the maximum flow available is 12 gallons per minute at 30 psi, and the sprinkler heads being used are rated for 1.5 gpm at 30 psi, no more than six sprinkler heads should be designed into the circuit. 2. Sprinkler heads on a circuit should all be of the same type and have the same purpose. a. If heads are mixed, there is a dilemma in setting the length of time and frequency for running the circuit. b. For instance, spray heads to irrigate an area of ground cover would put too much water on the ground in the time it takes a rotating streamer to adequately water a large section of turf. c. These applications and head types should not be mixed on the same circuit. 3. As elevation changes in the irrigation system, there is a corresponding change in water pressure. a. As elevation goes up from the water supply, there is a loss of 0.433 pounds of pressure for every foot in elevation increase. (This is often expressed as a half-pound loss for every foot higher in elevation.) b. The gain in pressure is the same: 0.433 psi for every foot lower from the source. c. For example, a sprinkler connected to a source with 40 pounds of pressure available at the required flow, would be operating on a little over 35 psi if the sprinkler head was at an elevation 10 feet higher than the source: 40 psi - [10 feet x 0.433 psi change / foot] = 35.67 psi 4. Pressure loss also occurs through friction with the pipe. a. The larger the pipe diameter, the less friction loss there is. b. Higher water velocity through a pipe results in greater pressure loss. In other words, high flow in a small pipe results in pressure loss. c. Total friction loss depends on pipe size and the length of the circuit. Tables can be used to calculate loss. This is usually not a problem on small residential installations if adequate size pipe is used. 5. When using the majority of sprinklers with rotating-heads, those with different coverages have to be placed on different circuits (for example, those set to cover a full circle as opposed to those set for quarter- or half-circles). a. Rotating heads of any one type put water out at the same rate, and travel across their arc at the same rate. b. Consequently, a head which is set for a half circle will yield a precipitation rate double that of a head set for a full circle. c. If these were on the same line, the area covered by the full- circle head would dry out well ahead of the area covered by the half-circle head. The full-circle heads should be run twice as long. This can only be done on separate circuits. 6. Sprinkler systems should be designed with head-to-head coverage. a. Sprinkler heads throw most of their water out away from the head, and rely on the next sprinkler over to cover turf near the head itself. b. Overlap is required for even water coverage. F. System Installation: When installing a sprinkler system, don't cut corners on effort or expense. A properly installed, trouble-free system will save a tremendous amount of labor and time. A step-by-step description of installation procedures is beyond the scope of this lesson, but some helpful points to remember are listed below: 1. Layout: Lay out the system according to the plan devised on paper. a. Use wooden stakes to locate the heads. b. Use gypsum to show where lines will run. c. Use string to keep straight lines where you want them, and use arched bender board to mark even curves. d. PVC will flex to some degree so don't be afraid to design slight bends into the pipe layout. This may be necessary to avoid walkways or other structures. 2. Trench: By all means use a trenching machine for this work. Not only will it save labor, but less of the subsoil will be disrupted, and fewer problems with settling will be encountered. Other points: a. Main (pressurized) lines should be buried at least 12" (and many codes specify 18"), for most residential situations. b. Lateral lines should be buried about eight inches. c. Use a 1" galvanized pipe to drive a hole under walkways and paved areas. Water pressure can be used to loosen soil, but this creates a mess. 3. Assembly: a. Work from the control valve out to the heads. b. Use a tray to keep all of the tools needed for PVC assembly together. The tools and materials you should have are: 1) A good PVC shear. These are faster and cleaner-cutting than saws. They leave no burrs on the cut. If you are using a saw, have sandpaper on hand to clean off burrs. 2) A tape for measuring pipe lengths. 3) Clean rags for wiping fittings and excess cement. 4) A pair of channel-lock pliers and small pipe wrenches, for installing threaded fittings. 5) A supply of teflon tape for threaded fittings. (ALWAYS tape threaded fittings.) 6) Primer for cleaning and softening PVC. 7) PVC cement for welding slip fittings. 8) All of the fittings needed to do the job. c. Some important points on assembling PVC fittings: 1) Make sure fittings and pipe are free of dirt and debris. 2) If required by code, clean and soften pipe with primer. 3) Working quickly, apply a layer of cement to both the pipe end and the inside of the fitting. Make sure coverage is complete. 4) Push pipe into the fitting, turning the pipe about 1/4 turn as you go in to assure a good weld. Push pipe in until it "bottoms out." 5) Hold the weld in place for about 10 seconds. Some fittings have a tendency to push the pipe back out if it is not held in place. 6) Wipe off excess cement from around the fitting. d. When finished with assembling the system, flush out dirt and dust before attaching the heads. e. Allow welded joints to set for about 6 hours before pressure testing the system. 4. Test: Be sure to test the system completely BEFORE refilling the trenches. a. Check for leaks, proper operation of pop-ups, and consistency in the spray pattern. b. Add heads or circuits if necessary. 5. Backfill: Fill in the trenches. a. After backfilling over 3/4 of the trench, flood the trenches to help settle soil. b. After water has drained off, fill in the rest of the trench with the remaining soil. G. System maintenance: Even the most carefully installed systems require periodic maintenance: 1. General Maintenance: Check these items routinely, at least once a year, preferably in the spring. a. Check nozzles for even spray patterns. Nozzles clog easily and need cleaning out periodically. b. Flush filters. The frequency of this chore depends on water quality. c. Check pop-ups. Sometimes pop-ups are reluctant to retract and need adjustment or lubrication. d. Change the back-up battery on the controller annually. This will save programming headaches if there is a power disruption. 2. Troubleshooting: Sometimes unexpected problems crop up with a system. Some common problems and probable causes: a. A wet spot develops around the lowest elevation head on a circuit: The usual cause of this is a valve which is not closing completely. Check for foreign matter in the valve, and check seals. b. Dry spots develop in a lawn: This indicates a breakdown in the spray pattern. The usual cause is a clogged nozzle, or a stuck pop-up that won't pop up. c. The entire circuit or system is too wet or too dry: This may be caused by a bad setting in the controller, perhaps due to a power disruption. Check controller program. PART III: DRIP SYSTEMS A. Description: Drip irrigation systems enable the slow and precise application of water to the roots of plants, resulting in a minimum loss of water to evaporation, overspray, and runoff. 1. Applications: Drip irrigation is a flexible, adaptable irrigation method. There is a wealth of equipment and fixtures to enable the user to irrigate otherwise difficult situations. a. Drip is used primarily for irrigation of shrubs, trees, and containers such as planter boxes. b. It is particularly helpful in watering hanging baskets out of doors, and is a very good solution to irrigating on slopes where runoff is a problem. Drip is ideal for roof and patio gardens. It can also be used with certain ground covers. c. Drip will not work for watering turf in any but the smallest area. Drip irrigation is not good for the widespread, even application of water. 2. Advantages: Drip irrigation provides elegant solutions to many of today's difficult irrigation problems, especially where the water supply is strained. a. Drip irrigation enables precise placement of water. There is no overspray, and the wind doesn't interfere with most drip watering. b. Drip irrigation can be used in uneven terrain. Level surfaces are not necessary as with flood and furrow irrigation techniques. c. Drip is particularly good for irrigating a sloped area. Where sprinkler-applied water would run off, drip irrigation can be applied at the same rate the soil can absorb it, even on a steep slope. d. Drip is flexible. Because it is not (usually) buried below ground, it is easy to make additions and changes to drip irrigation. It is also easy to access if repairs are needed. e. Drip systems are easier to design than sprinkler systems. Because drip systems run on low pressure and low flow, designing a drip system is less risky. It is easy to add more outlets without so much risk of running out of water or pressure. f. DRIP SAVES WATER! Areas which do not require watering are not watered. This means there are fewer weeds to remove moisture from the ground. Also, there is a reduction in evaporative loss and runoff. 3. Disadvantages of Drip Irrigation Systems: a. Drip irrigation cannot deliver large volumes of water if they are needed, such as in large turf areas. b. Drip systems are not recommended for areas with vehicular or foot traffic because they are more subject to damage. They are usually made of more fragile components than sprinkler systems, and because they are often at or near the surface, can be damaged more easily. (Gophers like to chew through polyethylene drip tubing!) c. It is difficult to tell when drip irrigation systems are not working. d. Drip irrigation systems need filters more frequently than sprinkler systems do. B. General Principles and Uses of Drip Irrigation: 1. Drip systems operate at relatively low pressures (20-25 psi and lower). 2. Drip systems require relatively low flow rates. A water supply which can deliver only four gallons per minute could have, literally, over a hundred drip emitters on one circuit all watering different plants at the same time. 3. Drip systems deliver low precipitation rates: a. This means drip circuits must generally be left on for long periods of time to water plants thoroughly. b. Low precipitation rates also mean lower infiltration rates are permissible in the soil being irrigated. 4. System design is easy to manage with drip irrigation. a. There is usually far more pressure and flow available for a typical residential or small commercial landscape, than is required at one time by a drip system. b. Even if mistakes are made in design, elements can be removed or added to a drip system with relatively little trouble. 5. Varying the amount of water delivered with a drip system can be controlled in several ways. For instance, areas requiring more water can have: a. Emitters with higher flow rates installed. b. More emitters added in the same vicinity. c. More time that the drip system is left on (increased run time). d. More frequent irrigations. All of these options result in more TOTAL precipitation. 6. Water is placed only where it is needed through the use of emitters, mini-sprinklers, and soaker tube. C. Water Supply: As suggested above, it is easier to supply most drip systems with water than to supply sprinkler systems, but there are some guidelines: 1. Adequate Flow: Some drip systems can run on flows as low as one gallon per minute, depending on how much needs to be watered at once. a. Remember, though, that most typical landscapes need sprinklers, in addition to drip, to adequately irrigate the whole landscape. b. It is best to try to provide for good flow if at all possible. This will provide for later expansion if desired. 2. Adequate Pressure: Pressure of about 20 psi is enough for most drip equipment. Some emitters and tubing specify less pressure, so pressure regulators must be added in line. 3. Adequate Water Quality: Drip has generally high requirements for water quality: a. The orifices used for drip equipment are narrow and clog easily. b. If water has any sand, silt, or rust coming through at the source, filters must be used or the irrigation system will not function properly. c. Salts can crystalize and accumulate at water outlets. Drip systems using hard water will have to be maintained more carefully. D. Components of a Drip System: The components of a drip irrigation system are much the same as a sprinkler system, with some notable exceptions. The controller, the gate valve, the backflow preventer, the valves, the pipe, and the below-ground fittings are all essentially the same as with sprinklers. (Please refer to (CLF6453) Sprinkler Irrigation Systems for a review of these items.) Below is a description of the components which differ, or are unique to drip irrigation systems. For more detailed information on the components of a drip irrigation system, please refer to topic plan (CLF6454) Drip Irrigation Systems. 1. Filters: The need for a filter is more acute with a drip system than with most sprinklers. A filter will keep debris out of the tiny orifices used in the many emitters. 2. Pressure Regulator: Drip equipment is designed for specific operating ranges, usually low pressures. A pressure regulator is almost always needed to bring the regular water supply down to a manageable range. 3. Tubing: Instead of stiff PVC, drip systems rely on flexible, black polyethylene (PE) tubing. 4. Fittings: Because drip fittings are neither glued nor threaded, and because the 1/2 inch format is so widely used, the array of drip fittings is greatly simplified: 5. Emitters: Emitters simply drip or spill water out onto the ground slowly, at a prescribed rate. The range of available drip emitters is great. Some basics: a. Flow rates range from about 1/2 gallon per hour to around 5 gallons per hour. b. Pressure-compensating emitters are available to standardize flow. While not necessary in most situations, pressure compensating emitters should be used along a line which goes up and down a slope, or on a long line, (more than 200 feet in length). 6. Specialized Devices: There are a number of other devices besides regular drip emitters available for low-pressure/low-flow irrigation. a. Spray attachments: These spray water like a sprinkler, only on a much smaller scale. These units generally demand more water (higher flow) that conventional emitters because they are soaking a larger area. b. Driplines: These allow water to seep out along a continuous line. Attached to the 1/2" lateral with a transfer barb, they can be used to water a vegetable bed, a hedgerow, or any other dense planting. E. System design: One of the great advantages of drip irrigation is its flexibility and relative ease of design. While there are a few similarities to sprinkler irrigation, there are some significant differences in design considerations: 1. Like sprinkler systems, drip systems are divided into "circuits," but fewer circuits are generally required. a. This is because the low flow requirement of the emitters allows much more plant material to be irrigated on one circuit. b. Often, a landscape will have several sprinkler circuits watering different areas of turf and ground cover and one or two drip circuits will pick up the entire remainder of the landscape. 2. Unlike sprinkler systems, a variety of emitter types can be put on one circuit. If plants need more water, simply changing emitters or adding an extra will solve the problem. 3. Pressure variations have to be accounted for with pressure regulators and pressure compensating devices: a. As with sprinklers, elevation changes in the irrigation system result in a corresponding change in water pressure. b. Pressure loss also occurs through friction with the pipe. However, because of relatively low water velocities, friction loss is only a problem in long runs of tubing. c. (Refer to (CLF 6453) Sprinkler Irrigation Systems for more information on pressure loss.) 4. When using mini-sprinklers, overlap is required if uniform coverage is to be had, just as is the case with regular sprinkler systems. 5. The system can be added to as needs arise, without having to be "designed" in advance: a. As plants mature and require more water, additional emitters can be added. b. Keep a running tab on the number and ratings of emitters installed, so you know when you are approaching the limit of the available flow on each circuit. F. System Installation: Installing a drip system is very simple. There is a tinker-toy quality to assembling drip systems which makes them fun to put together. If a mistake is made, a goof plug or a coupling can usually fix the problem. A step-by-step description of installation procedures is beyond the scope of this lesson, but some helpful points to remember are listed below: 1. Layout: Lay drip line out near plants to be watered: a. Try to lay line where it will not be seen or walked over. Drip assemblies are subject to damage if tripped over or if emitters are stepped on. b. To make coiled line easier to handle, allow it to lie in the sun before trying to move it into place. c. Drip tubing can be buried a few inches underground, if desired, to keep it out of sight. Trench lightly as necessary. 2. Assemble Tubing and Fittings a. Work from the control valve out, adding tees and elbows as necessary. b. Use a tray to keep all of the tools needed for tube assembly together. The tools and materials you should have are: 1) A pair of pruning shears or equivalent for cutting tubing. 2) A tape for measuring tubing lengths. 3) A supply of teflon tape for threaded fittings. (ALWAYS tape threaded fittings.) Also, teflon tape helps seal some barbed fittings. 4) Polyethylene pipe punches of various sizes, to punch holes for transfer barbs and emitters. 5) An assortment of the fittings needed to complete the job. 6) Optional: A supply of hot water for dipping pipe ends. This makes them softer and easier to fit. c. Some important points on assembling drip fittings: 1) Try to keep fittings and tubing free of dirt and debris. 2) Don't force tubing too far into compression fittings because this interferes with flow. One inch is far enough. 3) When you punch a hole for an emitter, try to punch a clean hole at a right angle. This will prevent a leaky connection. __________________________________________________________ ACTIVITY: 1. Gather an assortment of drip irrigation tubing, emitters, fittings, and assembly tools. Review the names of the various supplies, and have students practice fitting and taking apart the various system components. __________________________________________________________ 3. Flush the System: When assembly is complete except for placement of emitters, flush the system COMPLETELY. This is critical because emitters clog very easily with dirt entering through the water supply. 4. Install Emitters and Test: After the system is flushed, install all the emitters and test the system. a. Check for leaks. b. Check for correct emitter function. 5. Mulch: If desired, the tubing can be mulched over to hide it from sight, and to conserve additional moisture. G. System Maintenance: Drip system maintenance is simple but critical. Unlike sprinkler irrigation, there is little overlap in a drip system, and if an emitter gets clogged, a plant can go completely without water. Some requirements: 1. On a semi-monthly basis, check the flow from each emitter. This is obviously more critical in hot summer months. 2. Twice a year flush the lines by taking off the end cap and allowing water to run out freely. 3. Clean out the water filter occasionally. Frequency depends on water supply. 4. Salts buildup can be removed from emitters by soaking them in vinegar overnight and scrubbing with a toothbrush. __________________________________________________________ ACTIVITY: 1. Using the site maps developed during the first activity at the beginning of this lesson, have students design an irrigation system to irrigate the existing plantings. Students can use specifications from the manufacturers' literature obtained earlier. 2. Students should be encouraged to design both sprinkler and drip components into their system. 3. Those finishing early should be asked to draw an irrigation plan for a modified landscape plan, reflecting improvements over the existing site as originally mapped. These improvements should be of the student's own design. __________________________________________________________ 1/7/91 MH/clh #%&C