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Energy Efficient Homes: The Irrigation System1

Melissa B. Haley, Michael D. Dukes, Stacia Davis, Mary Shedd, and Bernard Cardenas-Lailhacar2

Did you know that the typical homeowner uses up to 50% of a home’s total water consumption for irrigation and often overirrigation?

If you have a 5,000 square foot yard and use an in-ground sprinkler system, you may be spending $5 to $25 every time you irrigate. Overwatering the lawn and landscape is a common mistake many homeowners make. However, keep in mind that, like most homeowners using public water, you are charged twice for the water you use—one time for freshwater coming in, and a second time for the estimated wastewater that you discharge.

Quick Facts

  • Automated, in-ground irrigation systems have been shown to use 47% more water than non-automated, above ground systems (Mayer et al., 1999).

  • Many irrigation systems leave “dead spots” in the lawn due to poor design resulting in overirrigation efforts to keep the entire lawn healthy.

  • Using an irrigation schedule based on the seasonal water needs of the landscape reduces water use without compromising plant quality.

  • Rain shutoff devices such as rain sensors and soil moisture sensors reduce the number of unnecessary irrigation events.

  • An irrigation schedule based on real-time water needs of the landscape can be determined automatically by using an evapotranspiration (ET) controller instead of a typical time clock.

Terms to Help You Get Started

Application Rate—Total volume of water applied in a given time period over an area; expressed as a depth per hour, also sometimes called precipitation rate

Effective Rainfall—The rainfall that is stored in the root zone of the lawn/landscape and should be considered before supplementing with irrigation; this does not include rainfall that contributes to runoff or drainage

Evapotranspiration (ET)—The total water lost from the soil (evaporation) and from the plant surface (transpiration) over some period

Efficiency, Irrigation Water Use—Ratio of the amount of water actually required by plants to the amount of water extracted from a water source for irrigation

Efficiency, Irrigation System—Ratio of the amount of water dispersed to the amount of water actually received by the target area

ET (Weather-based) Controllers—Irrigation controllers that calculate ET from on-site weather data by the controller (stand-alone) or from a “nearby” weather station and sent by signal to the controller (signal-based)

Drip Irrigation—Micro-irrigation system (low pressure and low volume) where water is applied on or below the soil surface as drops or small streams through emitters

Field Capacity (FC)—Maximum amount of water a soil may hold before draining (measured as percentage or inches per foot of soil)

Hydro-Zone—Plants grouped by water needs, organized into one irrigation zone.

Irrigation Controller or Timer—An automatic timing device that operates irrigation zones for a predetermined time and frequency (days per week)

Irrigation Scheduling—Determining when and how much to irrigate, based on factors such as soil type, root zone depth, and local weather conditions

Irrigation Zone—Area of an irrigation system operated by one control valve

Micro-irrigation—Application of small quantities of water directly to or below the soil surface; includes drip, bubblers, and low-volume spray irrigation (micro-sprinkler)

Potable Water—Water fit for drinking

Rain Sensor (RS)—Device that can bypass the irrigation controller settings when a specific amount of rainfall has occurred

Rain Shut-off Device—Any device designed to bypass an irrigation event after an adequate amount of precipitation has occurred

Riser—Length of pipe usually affixed to a lateral line or sub-main pipe to support a sprinkler

Reclaimed Water—Used water that is reused after receiving at least secondary treatment from a wastewater treatment facility

Runoff—Rainfall or irrigation water that is not absorbed by the soil, but flows off the lawn/landscape area

Run time—Length of time a single irrigation zone operates

Smart Controller—Technological device (includes rain sensors, soil moisture sensors, and ET controllers) that uses weather data or soil moisture readings as feedback from the irrigated system to schedule irrigation

Soil Moisture Sensor (SMS)—Sensor buried in the root zone that measures soil water content

Soil Moisture Based Irrigation Controller (Bypass configuration)—Device that connects the SMS to the irrigation timer and bypasses the automatic irrigation when the soil moisture content is adequate for plant needs

Soil Moisture Based Irrigation Controller (On-demand configuration)—A controller that uses SMSs to regulate water content in the plant root zone between low and high moisture thresholds

Solenoid Valve—Electric valve connected to a timer that facilitates the operation of the irrigation zones

Timer—See Irrigation Controller

Uniformity—The evenness of water application to a target irrigation area

Valve—Irrigation device that opens and closes to allow or not allow water into specific pipes; can be either manual or electric

Water Meter—Measures water volume (typically in gallons)

Why does irrigation water conservation matter?

Although Florida has a humid climate (the average annual precipitation rate is greater than the evapotranspiration rate), spring, fall, and winter are normally dry. The average annual precipitation in Florida is approximately 52 inches with most rainfall occurring in the summer months (June through August). The spring months (March through May) are typically the hottest and driest (USDA, 1981). This region is also characterized by sandy soils with a low water-holding capacity; therefore, storage of water is minimal. These characteristics—dry and hot spring weather and sporadic large rain events in the summer, coupled with the low water-holding capacity of the soil—make irrigation necessary for the high-quality landscapes desired by homeowners.

Water used in a residential setting comprises 61% of the potable water used by the public. This public supply category is responsible for the largest single portion (43%) of all groundwater withdrawal in Florida (Marella, 1999). This amount of groundwater use is even larger than the agriculture or industrial categories.

A landscape and irrigation study in the Central Florida Ridge found that, on average, 62% of potable water was used for landscape irrigation (Haley et al., 2007). Other recent research in Florida has indicated that homeowners irrigated too much in the late fall and winter due to the inconvenience of changing the time clock or due to a general misunderstanding of how much water to apply during the year.

The average residential irrigation cycle consumes several thousand gallons of water during each irrigation event. Water conservation has become a major concern for Florida, as the water demand increases while the limited available supply per capita decreases.

How can I save water and money, yet still have an irrigation system?

  • Check to see if there is an operating rain sensor and/or “smart” controller device on the irrigation system. These devices ensure that the landscape is watered only when needed, and that the system will shut-off during/after a rainfall event, or when the soil has sufficient water content. In 1991, the Florida Legislature passed a Bill (HB91), which required any person installing an “automatic lawn sprinkler system” to install a rain sensor device or switch (also referred to as a rain shutoff switch)—see Florida law (section 373.62, Florida Statutes) for full wording. In some municipalities, this is also required on all existing automatic irrigation systems (i.e., including systems installed prior to 1991). For more information about sustainable landscapes and communities see Policies that Address Sustainable Landscaping Practices at http://edis.ifas.ufl.edu/UW253, and Evaluating Green Communities: Top Eleven Questions to Ask at http://edis.ifas.ufl.edu/UW247.

  • Design the irrigation system so that irrigation zones for turfgrass are separate from other landscape plants. In general, turfgrass needs more frequent irrigation than established shrubs and trees. Therefore, if you have the same irrigation zone for both, you could water the turf correctly while over-watering the shrubs and trees. In fact, once established, most shrubs and trees do not require additional irrigation unless there is a drought.

  • Schedule irrigation appropriately, this means answering:

(1) How much water should be applied?

(2) When should it be applied?

  • The answers to these two questions should be based on water needs of particular plants in the landscape, as influenced by the environment (such as local weather conditions) and site-specific factors (such as soil and root zone).

  • Significant reductions in water used for irrigation purposes can be achieved by properly scheduling irrigation and making landscape changes. Recommendations for run times are available from UF/IFAS Extension. The run times are listed by month for geographic location, application rate, and sprinkler type; assuming head-to-head coverage and weather conditions that are characteristic to Florida.

  • The Florida Automated Weather Network has an Urban Irrigation Scheduler that can make scheduling very easy (see Web site http://fawn.ifas.ufl.edu/tools/urban_irrigation/ ). For other EDIS documents that will help you with irrigation scheduling see Turf Irrigation for the Home at http://edis.ifas.ufl.edu/ae144, Operation of Residential Irrigation Controllers at http://edis.ifas.ufl.edu/ae220, Irrigating Landscape Plants During Establishment at http://edis.ifas.ufl.edu/ae287, Home Irrigation and Landscape Combinations for Water Conservation in Florida at http://edis.ifas.ufl.edu/ep113.

Micro-irrigation in bedded areas (Figure 1) results in more efficient water application, because it targets the root zone of the plants, irrigating 50% or less area. Combining both proper irrigation scheduling and design can improve irrigation water conservation.

Figure 1. 

Example of micro-irrigation


Credit: Michael Dukes
[Click thumbnail to enlarge.]

  • An irrigation system evaluation can help you save water by improving the irrigation systems efficiency through maintenance. System evaluations (or audits) can be performed by a state Mobile Irrigation Lab (http://www.floridaagwaterpolicy.com/MobileIrrigationLabs.html) or by the homeowner.

  • As part of an irrigation evaluation, the uniformity of water volume applied to the lawn is measured with catch-can tests (Figure 2). Uniformity is increased with proper head-to-head coverage. Good uniformity combined with proper scheduling will result in reduced pest and weed invasion as well as fewer “dry spots.” Although a system can have sufficently good uniformity, that does not mean that the irrigation event will necessarily be efficient.

Figure 2. 

Irrigation uniformity bucket test


Credit: Melissa B. Haley
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Efficiency vs. Uniformity

The terms “efficiency” and “uniformity” are often confused when discussing irrigation. It is a common mistake to use them synonymously. “Efficiency” refers to how much of the water applied to the plants is finally used by them, while “uniformity” refers to how evenly the water is applied to the plants. Figure 3 illustrates this concept.

Figure 3. 

Efficiency versus uniformity in landscape irrigation (A)Top picture shows the soil reservoir or root zone. (B)Middle left is uniform and efficient (the goal). (C)Middle right is non-uniform and while efficient in terms of conservative water use results in plant quality decline. (D)Bottom left is non-uniform and inefficient due to over watering some areas. (E)Bottom right is uniform but inefficient due to over-watering resulting in drainage below the root zone (which, with time, can result in plant loss as well as the transport of excess nutrients, fertilizers and pesticides that harm the environment.)


Credit: Michael Dukes
[Click thumbnail to enlarge.]

There are a number of solutions for improving the efficiency of your irrigation system. Use the following checklist to help you get started.

Checklist for Efficient Irrigation

  • Perform regular maintenance by turning on all irrigation zones. Check for leaks and that all irrigation heads are operating properly.

  • Avoid the six most common irrigation errors:

    1. Broken or misdirected sprinklers

    2. Sprinklers application obstructed by plant parts or grass blades. These include branches, trunks, or leaves that can cause the spray pattern to be uneven.

    3. Mixed sprinkler types. For example, having spray heads and rotors in the same zone. These two sprinkler types have different application rates, and each one is generally intended to irrigate different types of plants. When stationary shrub spray-heads and rotating turf sprinklers are used in the same irrigation zone, the shrubs usually end up being overwatered.

    4. Unmatched precipitation rates. The flow rate of a sprinkler covering 90 degrees should be half the amount of the same type of sprinkler covering 180 degrees.

    5. Improperly spaced sprinklers. Space the lawn sprinklers so the water from one head reaches the next surrounding sprinkler head(s), ensuring full coverage.

    6. Irrigation scheduled incorrectly. Irrigation controllers are often set to run too frequently or for too long per irrigation event. Consequently, turfgrass and landscape plants are over-irrigated, water is wasted, fertilizers are washed away, and diseases are promoted. Water only as needed.

  • Adjust irrigation zones/sprinklers to avoid spraying buildings, driveways, streets, and sidewalks. In addition, be certain that plants or structures do not interfere with irrigation spray patterns.

  • Make sure that there is a functioning rain shut-off device placed in an effective location (i.e., so that rainfall collection will not be impeded).

  • Use a dual programmable timer to irrigate different areas of the landscape for different lengths of time.

  • Separate the irrigation system into multiple zones to water only those areas that need it.

  • Use micro-irrigation systems (sometimes called low-volume irrigation) on ornamental planting areas, which use water more efficiently by dispensing water slowly near the base of the plant, thereby reducing runoff and evaporation.

  • Check on the availability and legality of reclaimed water, cistern water (from rainwater harvesting), or other non-potable source for irrigation water.

  • Call your water utility company, a local irrigation contractor, county extension office, or your local Natural Resources Conservation Service (USDA/NRCS) to see if they can provide an irrigation system evaluation through the Mobile Irrigation Laboratory or some other method.

What is evapotranspiration?

Evapotranspiration (ET) is the rate at which water may be removed from soil and plant surfaces to the atmosphere by a combination of evaporation and transpiration. Evaporation (E) is the conversion of water into its vapor phase. The main factors influencing evaporation are the supply of energy by solar radiation (from the sun) and the transport of vapor away from the surface (e.g., by wind). Transpiration (T) refers to the water used by plants and is affected by plant physiology and environmental factors. The evapotranspiration process is climate controlled.

To learn about controlling for evaporative losses during irrigation, see Evaporation Loss During Sprinkler Irrigation at http://edis.ifas.ufl.edu/ae048. To determine the ET for your area, refer to the Florida Automated Weather Network (FAWN) at http://fawn.ifas.ufl.edu. Finally, the concept is described in further detail in Evapotranspiration: Potential or Reference? at http://edis.ifas.ufl.edu/ae256.

How an Irrigation System Is Set Up, Including Conservation Devices

Figures 4 through 8 pictorially depict how automatic irrigation will function when wired with conservation devices such as rain sensors, soil moisture sensors, and ET controllers.

Figure 4. 

Irrigation timers are wired to valves in the ground that allow irrigation to occur when scheduled


Credit: Haley et al
[Click thumbnail to enlarge.]

Figure 5. 

Irrigation timers connected to rain sensors allow irrigation events when the sensor is dry


Credit: Haley et al
[Click thumbnail to enlarge.]

Figure 6. 

Irrigation timers connected to rain sensors bypass irrigation events when the sensor is wet; irrigation events resume as scheduled when the sensor dries out


Credit: Haley et al
[Click thumbnail to enlarge.]

Figure 8. 

Signal-based ET controllers use local, publicly available weather data to calculate ET used to determine the irrigation schedule


Credit: Haley et al
[Click thumbnail to enlarge.]

Figure 7. 

An irrigation timer with soil moisture sensor (SMS) allows irrigation events when the soil is dry


Credit: Haley et al
[Click thumbnail to enlarge.]

Figure 8. 

Signal-based ET controllers use local, publicly available weather data to calculate ET used to determine the irrigation schedule


Credit: Haley et al
[Click thumbnail to enlarge.]

Another document that will help you understand how your irrigation system and controllers are set up is Selection and Use of Water Meters for Irrigation Water Measurement (http://edis.ifas.ufl.edu/ae106).

Water Conservation Devices

Debunking Urban Myths

  1. Rain sensors: everybody knows they don't work, so why bother? Actually, rain sensors resulted in a 34% savings during normal/wet weather conditions (Cardenas-Lailhacar and Dukes, 2008) and a 15% savings during dry weather conditions (Haley and Dukes, 2007).

  2. Soil moisture sensors: these things are not worth the money. Savings could provide a payback in one to two years and resulted in 69%–92% savings during normal/wet weather (Cardenas-Lailhacar et al., 2008).

  3. ET controllers: they are appropriate for California weather conditions, but not for Florida. Initial research has shown that they are also effective for Florida's climate (Davis et al., 2007).

Rain Sensors

Rain sensors, the simplest rain shut-off device, are designed to bypass a scheduled event from an automatic irrigation system timer after a specific amount of rainfall has occurred. They are small, inexpensive devices that are wired to the irrigation system timer. In order to ensure proper functionality, rain sensors should be mounted in an open area where they are exposed to rainfall.

For more information, see Residential Irrigation System Rainfall Shutoff Devices (http://edis.ifas.ufl.edu/ae221).

Soil Moisture Controllers

Soil moisture controllers are designed to bypass a scheduled event from an automatic irrigation system timer if the soil water content is above a certain threshold. This threshold is defined and set by the user. The sensor buried within the turfgrass or landscape root zone checks the soil water content (Dukes et al., 2005).

What does an ET controller do?

ET controllers are irrigation devices that schedule irrigation instead of using run times programmed by the homeowner. These controllers use daily ET and rainfall to determine the landscape water needs. Daily ET amounts will vary with the season, typically being high in the summer and low in the winter, and schedules are gauged for the plant's water requirement. This will result in more irrigation applied when less water is available to the plants.

Each controller works differently depending on the manufacturer but typically can be programmed with site-specific conditions such as soil type, plant type, sprinkler type, and sun and shade. The controllers are designed to either replace the typical timer or act as an amendment to the timer. Some controllers have accessories that make them more accurate, while others come as a complete package and need no additions. Depending on how the controller obtains ET information, yearly signal fees could be necessary.

Conservation Devices and Day-of-Week Restrictions

These devices can all be used successfully in conjunction with day-of-week watering restrictions. As shown above, the rain sensors and soil moisture controllers are wired to the standard irrigation time clock. The irrigation timer initiates the irrigation events, and therefore your appropriate watering days can be scheduled. A key concept to remember is that if the rain sensor setting or soil moisture sensor's threshold setting is queued correctly and determines that an irrigation event should be bypassed, overriding the system and irrigating on that day will result in runoff or excess drainage. Likewise, ET controllers allow for the user to program in permissible watering days and hours, and it adjusts the watering schedule accordingly. When these devices are set correctly, not only will you reduce unnecessary irrigation, but also turf quality will not be adversely affected.

Improper Irrigation

There are many potential risks to improper and inefficient irrigation design and water application. See examples in Figures 9 through 13 for a few common design-related issues.

Figure 9. 

Over irrigation results in runoff


Credit: Michael Dukes
[Click thumbnail to enlarge.]

Figure 10. 

Irrigating this small strip of turfgrass with too large a spray head and excessive radial coverage results in water waste


Credit: Michael Dukes
[Click thumbnail to enlarge.]

Figure 11. 

Water pressure that is too low provides uneven watering


Credit: Bryan Unruh
[Click thumbnail to enlarge.]

Figure 12. 

Iron stains on the fence show the use of an irrigation radius that is too large for this area


Credit: Bryan Unruh
[Click thumbnail to enlarge.]

Figure 13. 

Irrigation spraying side of house


Credit: Michael Dukes
[Click thumbnail to enlarge.]

References and Resources

Cardenas-Lailhacar, B., and M. D. Dukes. (2008). “Expanding Disk Rain Sensor Performance and Potential Irrigation Water Savings.” Journal of Irrigation and Drainage Engineering, 134(1), 67–73.

Cardenas-Lailhacar, B., M. D. Dukes, and G. L. Miller. (2008). “Sensor-Based Automation of Irrigation on Bermudagrass During Wet Weather Conditions.” Journal of Irrigation and Drainage Engineering 134(2), 120–128. Retrieved from http://abe.ufl.edu/faculty/mdukes/pdf/publications/SMS/Cardenas-SMS-paper-JID.pdf

Davis, S. L., M. D. Dukes, S. Vyapari, & G. L. Miller. (2007, May). “Evaulation and Demonstration of Evapotranspiration-Based Irrigation Controllers.” Proceedings ASCE EWRI World Environmental & Water Resources Congress, Tampa, FL. Retrieved from http://abe.ufl.edu/faculty/mdukes/pdf/publications/ET/EWRI-2007-ET-based-controllers-final.pdf

Dukes, M. D., & D. Z. Haman. (2013). Residential Irrigation System Rainfall Shutoff Devices. Gainesville: University of Florida Institute of Food and Agricultural Sciences. Retrieved from http://edis.ifas.ufl.edu/ae221

Dukes, M. D., Cardenas-Lailhacar, B., & G. Miler. (2007). Irrigation Research. Retrieved June 27, 2008, from http://abe.ufl.edu/mdukes/

Haley, M. B., & M. D. Dukes. (2007). “Residential Irrigation Water Application Influenced by Socio-Economic Parameters.” Paper Presented at 28th Annual International Irrigation Show, San Diego, CA.

Haley, M. B., M. D. Dukes, & G. L. Miller. (2007). “Residential Irrigation Water Use in Central Florida.” Journal of Irrigation and Drainage Engineering 133(5), 427–434. Retrieved from http://abe.ufl.edu/faculty/mdukes/pdf/irrigation-efficiency/Haley-FL-residential-irrig-JID.pdf

Marella, R. L. (1999). “Water Withdrawals, Use, Discharge, and Trends in Florida, 2000.” Scientific Investigations Report 2004-5151. Reston, VA: U.S. Geological Survey.

Mayer, P. W., W. B. DeOreo, E. M. Opitz, J. C. Kiefer, W. Y. Davis, B. Dziegielewski, & J. O. Nelson. (1999). Residential End Uses of Water. Denver: American Water Works Association Research Foundation. Retrieved from http://www.waterrf.org/PublicReportLibrary/RFR90781_1999_241A.pdf

USDA. (1981). “Land Resource Regions and Major Land Resource Areas of the United States.” Soil Conservation Service Handbook. Washington, DC: United States Department of Agriculture.

Footnotes

1.

This document is FCS3274, one of the Energy Efficient Homes series from the Department of Family, Youth, and Community Sciences, UF/IFAS Extension. This material was prepared with the support of the Department of Environmental Protection, Florida Energy Office; however, any opinions, findings, conclusions, or recommendations expressed herein are those of the author(s) and do not necessarily reflect the views of the Florida Department of Environmental Protection. Original publication date June 2008. Reviewed July 2015. Visit the EDIS website at http://edis.ifas.ufl.edu.

2.

Melissa B. Haley, former graduate student; Michael D. Dukes, associate professor; Stacia Davis, former graduate student; Mary Shedd, former graduate student; and Bernard Cardenas-Lailhacar, research coordinator; Department of Agricultural and Biological Engineering; UF/IFAS Extension, Gainesville, FL 32611.


The Institute of Food and Agricultural Sciences (IFAS) is an Equal Opportunity Institution authorized to provide research, educational information and other services only to individuals and institutions that function with non-discrimination with respect to race, creed, color, religion, age, disability, sex, sexual orientation, marital status, national origin, political opinions or affiliations. For more information on obtaining other UF/IFAS Extension publications, contact your county's UF/IFAS Extension office.

U.S. Department of Agriculture, UF/IFAS Extension Service, University of Florida, IFAS, Florida A & M University Cooperative Extension Program, and Boards of County Commissioners Cooperating. Nick T. Place, dean for UF/IFAS Extension.