Sprinkler Irrigation in the Landscape

Irrigation is one of three powerful landscape management tools. (The others are fertilization and cutting, e.g., pruning or mowing.)

Landscape irrigation provides year round plant growth in warm climates, assists establishment, and effects a shift in the climax vegetation on a site to more long-lived and woody species. Xeric sites that would be naturally dominated by annuals and herbaceous plants, e.g., grasses can be made through irrigation to support a denser, more luxuriant canopy, which many clients favor.

Plants have inherited cycles of leafing, flowering, and seed dispersal, compatible with annual cycles of rainfall in their natural habitat. Irrigation, the artificial watering of the soil, drastically changes where and how plants grow.

The most widespread landscape plant in North America, Kentucky bluegrass (Poa pratensis), is a Eurasian plant which naturalized in urban lawns due to irrigation. For all practical purposes it wouldn't be here without irrigation. When people talk about having a "lawn as green as the Joneses" they are quoting an expression that originated in the Kentucky bluegrass belt, and this arose from sprinkler irrigation.

Ecologically, irrigation interacts with other major landscape management tools. Close cutting of turfgrass, which weakens the plant and prevents adequate root development, leads to minimal available soil moisture reserve. Therefore, close-cut turf wilts and dries out more readily, and more frequent irrigation is required. In using irrigation to maintain close-mown, luxuriant stands of turfgrass throughout the growing season, turfgrass areas demand more frequent irrigation than wooded areas. This is the opposite of the natural occurrence of grasslands in drier areas, and woodlands in wetter areas.

In a negative sense, the practices of mowing, watering, and fertilization act in a vicious cycle to weaken and change natural ecosystems. Plants such as the slash pine (Pinus elliottii) that are adapted to a wet-dry cycle often show decline and death under irrigation. In a positive sense, irrigation coordinates with other tools, so people can accomplish the kind of landscape that they like. Performed with precision and good judgement, irrigation can be quite efficient in providing a healthy landscape, with reduced impacts on natural resources and ecosystems.

Unfortunately, there is too much bad irrigation. For this reason, the landscape and turfgrass manager can play a pivotal role in serving the client by installing, retrofitting, and maintaining irrigation systems according to sound design principles.

1001 ways to have a really bad irrigation system

1. Undersize your source of water:
   Select a pump that can just barely supply your smallest zone when the system is first installed.
   
2. Doom the suction line. 
   Install the suction line near a fast growing tree. Within a few years, roots will push the line up out of the ground, so you'll always know where it is. That also helps aerify the irrigation water. The pump is guaranteed to suck air, if you can ever get it primed.
   
3. Mix, don't match.
   Use a combination of high precipitation spray heads and low precipitation rotary heads within the same zone. This ensures that dry spots dry out while wet areas drown.
   
   . . . more 1001 ways to have a really bad irrigation system . . .
   
4. Bury your valves.
   The easiest way of covering a valve is to just bury it. This way it will never be an esthetic nuisance, and if anyone ever does find it again, the handle will be so corroded it will just break off and not be a problem.
   
5. Provide vertical irrigation.
   South Floridians are accustomed to rust-stained walls. It's almost a badge of honor to have an expensive plate-glass window that you can't see out of, or a fancy corporate sign that is tarnished in rust. You can contribute to this phenomenon by placing undependable impact drive heads close to walls. The painters will enjoy steady employment, year after year.
   
6. Use the smallest pipe size you can find.
   The tighter you squeeze water, the higher the pressure. You can prove this rule of physics by putting your thumb on the end of a hose and seeing how much farther the water squirts.
   
   . . . more 1001 ways to have a really bad irrigation system . . .
   
7. Use even smaller pipes on long, narrow runs.
   This creates an attractive geometric series of green oases surrounded by brown.
   
8. If you have to use valve boxes, bury them, too.
   While placing the top of the valve box two or three inches deep is enough to hide it, deeper is better. In fact, you should place the valve box directly on top of the pipe, so that the pipe will support the valve box when you drive over it.
   
9. Mister heads need 80-100 pounds pressure.
   Why else are they called misters?
   
   . . . more 1001 ways to have a really bad irrigation system . . .
   
10. Water at about 4 p.m.
    This way you can see if the sprinklers are working when you drive home. Besides cooling the grass, motorists and bicyclists appreciate a refreshing shower.
    
11. When digging a trench, only wimps and nerds need a string line.
    The stronger irrigation technicians should be able to wrestle 4-inch PVC pipes into the most crooked ditch, gluing so-called straight fittings at incredible angles.
    
12. Use extra glue to cover gaps in pipes.
    Whether you think you got some sand in the fitting or you see a crack that just won't close, keep putting as much glue as possible on the outside as a form of insurance.
    
    . . . more 1001 ways to have a really bad irrigation system . . .
    
13. Space sprinklers twice their diameter.
    If the droplets from one sprinkler just touch the droplets from next sprinkler, you've got perfect coverage.
    
14. Extend the pipe to prevent breakage.
    If you have pipes breaking due to water hammer, you need to use a tee to extend the ends of the pipes beyond the sprinklers to take the stress.
    
15. Always use schedule 40 pipe.
    No matter the size of the pipe, schedule 40 is right.
    
    . . . more 1001 ways to have a really bad irrigation system . . .
    
16. Use both a foot valve and a check valve.
    This prevents leaks in the suction line.
    
17. When it's hot, water in the middle of the day.
    It cools the grass.
    
    (Exam question:  "What are the remaining 984 ways to have a really bad irrigation system?")
    

The most essential essentials of sprinkler irrigation.

1. Objectives
2. Physics of water
1. Pressure (psi, pascals, head-foot), force, energy, and velocity
1. atm=14.7 psi = 33.9 feet
2. Pressure is independent of area
3. Comparison with traffic flow
4. Comparison with electronics
2. Friction loss, turbulent flow
3. Mathematical conversions involving irrigation
1. Weight, volume, flow, pounds, gallons, gpm
   cubic foot = 7.48 gallons (U.S.); gallon water = 8.35 pounds
   cubic foot water = 62.4 pounds
2. Precipitation rate, coefficient of uniformity
3. Measurement of areas, acre, square foot, square meter
4. Chain formula
5. Other factors: percolation, infiltration
4. System components
1. Source of water
2. Pumps and pump curves, e.g. head-capacity
3. Pipes
1. Pipe materials: galvanized steel, iron, copper, plastics (PVC, ABS, PE, etc.)
   e.g., PVC 1220 = polyvinyl chloride Type I, Grade 2, 2000 psi design strength.
2. Pipe size: nominal pipe size, O.D., I.D., wall, I.P.S., length, Schedule (obsolete for irrigation pipe), Class (preferred), SDR
3. Pipe connections: slip, threaded, etc.
4. Friction loss tables
4. Main lines
1. Loop vs. straight
2. Pressurized vs. master control
3. Surge, hammer, cavitation
5. Fittings
1. Types of connections: ell, tee, adapters, bushings (or reducers), caps, plugs
2. Outlets and adapters (S, C, M, Fe, reducing, etc.)
3. Special terminology: threaded nipple, street ell, 90^o vs. 45^o etc., various repair and special couplings, e.g., saddle, clamp, clamp saddle, insert fittings, compression couplings
4. Symbols: e.g., 1/2" S x 3/4" Fe
6. Valves
1. Gate valves: rising stem vs. non-rising stem. Globe valves vs. angle valves.
2. Remote control valves
1. Electric diaphragm, normally closed
2. Hydraulic diaphragm, normally open
3. Other: hydraulic piston, electric thermal motor, pressure reducing
3. Swing check valves, anti-siphon valves, garden hose valves, drain valve, quick-coupling
4. Importance of sectioning the system: fixed supply, problems of friction loss (see system design, below)
7. Controllers
1. Electromechanical, electrical
1. Wiring: master switch
2. Valve wiring
3. Problem solving: lightning, failure of zones to open
2. Electromechanical, hydraulic control
1. Pressure
2. Problem solving: zones that always stay on
3. Filters
3. Solid state
4. Satellite
5. Scheduling: watering cycle start time, calendar programming, station timing
8. Sprinkler heads
1. Fixed, sideways pattern, e.g., spray heads wrongly called "misters." Parts: nozzle, adapter or guide, stem, body, flange, riser. Options: pop-up, matched-precipitation, partial-circle, low-angle heads, etc. Problems: obstructions, lateral support, runoff.
2. Rotary, stream patterns. Parts: nozzle, body, housing, driver arm and impact arm, reversing mechanism for impact drive heads or "knockers", and for the gear driven rotaries, gear case, gear train, water wheel, swirl plate, and drive shaft. Other power sources include cam drive and ball drive.
3. General comparison of fixed vs. rotary based on cost, precipitation rate, and susceptibility to corruption.
4. Other: quick couplers, bed spray heads, shrub sprays, bubbler, flood, micro emitters, subsurface, and adjustable risers.
5. Reading sprinkler tables and understanding performance characteristics, distribution patterns
5. System design
1. Measuring a plot plan: property details, water supply
2. Sprinkler placement: placing round circles in square holes
1. Equilateral or triangular vs. rectilinear spacing
2. Street fronts, corners, fences, trees
3. Zoning
4. Routing the main, sizing pipes and valves
5. Wiring, controller selection
6. Irrigation installation
1. Staking and stringing
2. Ditches: depth, width, uniformity, backfilling, clean up
3. Pipe connections: solvent welds, etc.
4. Valve boxes, controller housings
5. Setting heads
6. Specialty tools: valve key, nipple extractor
7. Practical considerations
7. Maintenance
1. Time clock considerations
2. Visual check
3. Capture

Guides and articles:

Jess Stryker's Irrigation Tutorials
http://www.irrigationtutorials.com/

Efficiencies of Irrigation Systems Used in Florida Nurseries.
http://edis.ifas.ufl.edu/AE087/

Research Publications - California State University Center for Irrigation Technology
http://wateright.org/publications.asp

Irrigation Systems Slideshow - New Mexico State University.
http://weather.nmsu.edu/Teaching_Material/soil456/irrgationsys/index.htm

Associations:

The Irrigation Association. The national trade association.  There are links to state associations.
http://www.irrigation.org/ia/main.html  

Irrigation & Green Industry Network.  Go to the irrigation section for information.
http://www.igin.com

Design software:

Software Republic Landscape design software and irrigation design software. RainCAD appears to be a useful program; shareware downloads.
http://www.raincad.com/

Manufacturers and suppliers:

Rain Bird - Irrigation Manufacturers, Sprinklers, Products, Landscape Systems  Rainbird is one of the other major manufacturers
http://www.rainbird.com 

Spears Manufacturing Co. Plastic pipe fittings and valves.
http://www.spearsmfg.com

SprinklerSpot - purchase online.
http://www.sprinklerspot.com/

TORO: Golf Course Management. Toro's main irrigation page
http://www.toro.com/irrigation 

Turf Bubbler Wick Irrigation -- The Evolution Begins!   An example of an alternative system, which is neither subsurface nor overhead.
http://www.turfbubbler.com

Valve Boxes, Valvebox, Irrigation Valve Box, Meter Boxes, Electrical Boxes Made By AEP Valvebox. Valve boxes are one of the often-overlooked essentials.
http://www.aepvalvebox.com

Weathermatic
http://www.weathermatic.com

Weathermiser - integrated system for evaporation, dew point, temperature, and wind sensing that eliminates all unnecessary timer programmed irrigation cycles saving an average of 30% off of outdoor water usage.
http://www.weathermiser.com

Books on Irrigation

Choate, Richard B. 1994. Turf Irrigation Manual. Weather-matic Division of TELSCO INDUSTRIES, Dallas, TX.

Pair, Claude H. (ed.) 1983. Irrigation. The Irrigation Association. Arlington, VA.

Pira, E. S. 1997. A guide to golf course irrigation system design and drainage. Ann Arbor Press, Inc. Chelsea, MI.

Sarsfield, A. C. 1966. The abc's of lawn sprinkler systems. Irrigation technical services. Lafayette, CA.