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Publication #CIR1421

Operation of Residential Irrigation Controllers1

Michael D. Dukes and Dorota Z. Haman2

Introduction

Automatic landscape irrigation systems have become quite common in Florida in recent years. Electronic irrigation controllers are used to control these systems; however, it is not always obvious how to program these controllers to apply the desired amount of irrigation water.

Irrigation Controllers

The document "Irrigation System Controllers" (IFAS Publication SS-AGE-22; on the Web at:http://edis.ifas.ufl.edu/AE077) discusses various types of typical irrigation controllers in detail. In general, commercially available controllers are mechanical, electromechanical, electronic, or computer based. Electronic controllers are commonly installed in residential and small commercial landscape irrigation systems. We will discuss the general operation common to most residential irrigation controllers. For details specific to a given controller the reader should refer to the owner's manual.

Electronic Controller Operation

Generally, electronic controllers allow flexible scheduling of irrigation systems (Figure 1).

Figure 1. 

Typical residential irrigation controller.


[Click thumbnail to enlarge.]

Some scheduling options provided by controllers are:

Days of the week

Controllers may be set for irrigation every day, every second day, every third day, etc. Typical controllers will allow for selection of certain days of the week in a "custom" option or frequency, such as "every 2 days," for setting frequency of irrigation. The "custom" option is the one normally used during times of water restrictions, when irrigation is limited to one or two days each week.

Run time

The amount of time that each zone runs may be set from several minutes to several hours. Generally run time should be less than 60 minutes for Florida's sandy soils. The exact time depends on system application rate which can be determined as discussed in the next section. Irrigating longer will lead to movement of water below the root zone, which wastes water.

Percent

Most controllers have percentage settings so that the relative time may be adjusted. For example, if the controller is set to run 60 minutes per cycle the controller may be set to water at 75%. This will result in 60 minutes * 0.75 = 45 minute run time. Likewise, the run times in the other zones will be reduced to 75% of the zone time setting. This is helpful in Florida when the summer rains begin and irrigation can be cut back.

Program

Controllers usually have the capacity to run multiple programs. For example, on program "A", the controller may be set to water six rotor zones for 60 minutes twice each week. If new plants are planted in a landscape bed, they may need more frequent watering to become established. In this case, program "B" can be used to water that zone every day of the week.

Application Rates

The application rate is an amount of water applied over an area, such as a yard with landscape plants and turfgrass, in a given amount of time. Usually this is expressed as inches per hour (in/hr) and implies an even application of water. The application rate of an individual irrigation zone must be known to properly set the irrigation controller.

There are several ways to find the application rate of an irrigation zone. It may be:

  1. given by the designer or contractor,

  2. calculated from system and or sprinkler specifications,

  3. calculated based on measurements of flow from a water meter, or

  4. measured directly by placing catch containers in the irrigated zone of interest.

1. Application rate given by the designer or contractor.

Although application rates of each individual zone should be calculated by the designer, in practice this is rare.

2. Application rate calculated from system or sprinkler specifications.

Application rate may be calculated from the system specifications according to the total area method (Equation 1) or from the sprinkler specifications assuming they are all alike according to the sprinkler spacing method (Equation 2). Actual application rates may not match calculated rates due to misadjusted sprinklers, wind drift, pressure problems, etc. For these reasons, it is preferred that the actual application rate be verified by measurement as described in the sections 3 and 4.

Total area method:

where:

AR = application rate (in/hr)

GPM = system or zone flow rate (gpm)

AREA = total or zone irrigated area (ft2)

Sprinkler spacing method:

where:

AR = application rate (in/hr)

GPM = individual nozzle flow rate (gpm)

ROW = spacing of sprinkler rows (ft)

COL = spacing of sprinklers within the rows (ft)

3. Application rate calculated based on measurements of flow from a water meter.

The application rate for each irrigation zone can be determined from flow meter records. If a separate irrigation meter is not installed (which is typical on most homes), the utility meter must be used for this method. To use the utility meter, conduct the test when water is not being used in the home. If a separate irrigation meter is available, household water use does not have to be considered for the test. If a well is used to supply the irrigation system, then a meter must be installed after the pump to use this method.

Example - The meter reading prior to irrigation of a single zone was 1895750 gallons and after irrigation the meter reading was 1900600 gallons. The amount of water used during the irrigation cycle was 1900600-1897750 = 2850 gallons. The irrigation time for the zone was 2.5 hours (2.5 hours * 60 = 150 minutes). The irrigated area is approximately square and was known to be approximately 6750 ft2. Now the average application rate for the irrigated zone can be calculated by Equation 3.

where:

AR = application rate (in/hr)

GAL = total volume of water measured by the flow meter (gal)

AREA = irrigated area (ft2)

TIME = total time of irrigation cycle (min)

According to Equation 3:

Although this method is relatively easy, unless it is performed for each zone it will not give the accurate representation of individual zones that is needed to set the controller. For example, rotors (see Figure 2) typically have application rates of 0.25-1.0 in/hr, while spray heads (see Figure 3) have application rates of 0.75-1.5 in/hr. Therefore, these equipment types should be tested separately.

Figure 2. 

Gear-driven rotor irrigation head.


[Click thumbnail to enlarge.]

Figure 3. 

Fixed spray irrigation head.


[Click thumbnail to enlarge.]

4. Application rate measured directly using catch containers.

Application rate can be measured directly by placing several containers in a given irrigation zone during an irrigation event (see How to Calibrate Your Sprinkler System, http://edis.ifas.ufl.edu/LH026). This is similar to testing the system uniformity (see Lawn Sprinkler Selection and Layout for Uniform Water Application, http://edis.ifas.ufl.edu/AE084). Essentially, the containers must be the same shape and size. Old coffee cans are one example of a good container for this purpose. The rim of the can should be above the turf and the cans should be level. At least six cans per zone should be used and they should be distributed randomly. Next, run the irrigation system over a normal cycle. Then you can calculate the application rate according to the following example.

Example - One irrigation zone is to be tested. Several catch cans are positioned throughout the zone such that overlap from other zones does not contribute to those cans. Average depth of water measured in the cans was 1.25 inches after an irrigation run of 45 minutes.

where:

AR = application rate (in/hr)

DEPTH = average depth in catch cans for any one zone (in)

TIME = run time of irrigation zone tested (min)

According to Equation 4,

Setting the Time on Irrigation Controllers

Once the application rate is known, then the irrigation controller can be set for a desired irrigation depth according to Equation 5 with the parameters defined as in Equation 4.

Table 1 gives the calculated times according to Equation 5 based on desired application amount or depth and the application rate of the individual zone or system.

Seasonal Setting of Irrigation Controllers

The objective of irrigation is to replenish the water in the plant roots to avoid excessive plant stress. For landscape plants, especially turf, where the objective is to maintain the appearance and not to produce the highest amount of biomass, it is usually sufficient to aim for 60 - 100% replacement of water in the root zone.

Augustin (see "Water Requirements of Florida Turfgrasses", IFAS Publication BUL 200) calculated the net irrigation requirement of turfgrass for several geographical areas and based on effective rainfall. Effective rainfall takes into account the low water-holding capacity of Florida's soils (see Watering Your Florida Lawn, http://edis.ifas.ufl.edu/LH025 and Turf Irrigation for the Home, http://edis.ifas.ufl.edu/AE144). Net irrigation requirement is the amount of irrigation water that must be delivered to the crop. This does not consider irrigation losses such as pipeline leakage, wind drift, non-uniform application, etc.

Tables 2-9 present a suggested irrigation controller time setting assuming two irrigation events per week, and an irrigation system efficiency of 60% for application rates of 0.50, 0.75, 1.00, 1.25, and 1.50 in/hr, respectively. Three regions are represented in Tables 2-9, north (Gainesville), central (Orlando), and south (Miami). In addition, three levels of replacement are presented. It is desirable to irrigate at the lowest possible level of replacement without an acceptable degradation in turf or landscape quality. Two irrigation events per week were assumed since this is a common practice due to water restrictions. Any irrigation time exceeding 60 minutes should be split into two applications at least four hours apart with the time in between applications during the day when the plants will use the water (i.e., morning and afternoon). If the measured or calculated application rate does not exactly correspond to those given in the table, use the closest rate. For example, a homeowner measures an application rate of 0.6 in/hr. The table with the 0.5 in/hr application rate (Table 3) would be used.

Setting Microirrigation Zones

Microirrigation zones are sometime called "drip" or "trickle" irrigation and are becoming popular for landscape beds due to their ease of use and low use of water. There are several types of microirrigation emitters (see Figures 4, 5, 6, 7). More information on those emitters and how they are defined can be found in "Retrofitting a traditional in-ground sprinkler irrigation system for microirrigation of landscape plants" (IFAS Publication ABE324; on the Web at: http://edis.ifas.ufl.edu/AE222). Typically microirrigation does not wet the entire root zone; therefore, the application rate concept does not apply. These emitters have various emission rates, usually in gallons per hour. General guidelines on how many gallons are required for landscape plants can be found in "Fertilization and Irrigation Needs for Florida Lawns and Landscapes" (IFAS Publication ENH860; on the Web at: http://edis.ifas.ufl.edu/EP110). Once the gallons required are known, then the irrigation controller may be set according to Equation 6, assuming one emitter per plant. Since application depth may be difficult to calculate, microirrigation zones should be set initially for one-hour run time, two times each week. These zones can be reduced 15 minutes each cycle every week until plants show stress.

where:

TIME = microirrigation run time (min)

GAL = volume of irrigation water required for a plant (gal)

GPH = emission rate of a drip emitter (gph)

Figure 4. 

Individual drip emitters.


[Click thumbnail to enlarge.]

Figure 5. 

Drip tube or tape.


[Click thumbnail to enlarge.]

Figure 6. 

Bubbler.


[Click thumbnail to enlarge.]

Figure 7. 

Microjet or microspray.


[Click thumbnail to enlarge.]

References

Turf Irrigation for the Home (IFAS Publication Circular 829; on the Web at: http://edis.ifas.ufl.edu/AE144)

Turf Irrigation With a Hose and Sprinkler (IFAS Publication AE265)

Reduced Irrigation of St. Augustinegrass Turfgrass in the Tampa Bay Area (IFAS Publication AE264)

Fertilization and Irrigation Needs for Florida Lawns (IFAS Publication ENH860; on the Web at: http://edis.ifas.ufl.edu/EP110)

Coping with Drought in the Landscape (IFAS Publication ENH70; on the Web at: http://edis.ifas.ufl.edu/MG026)

How to Calibrate Your Sprinkler System (IFAS Publication ENH61; on the Web at: http://edis.ifas.ufl.edu/LH026)

Watering Your Florida Lawn (IFAS Publication ENH9; on the Web at: http://edis.ifas.ufl.edu/LH025)

Water Requirements of Florida Turfgrasses (IFAS Publication Bulletin 200)

Irrigation of Lawns and Gardens (IFAS Publication Circular 825; on the Web at: http://edis.ifas.ufl.edu/WI003)

Lawn Sprinkler Selection and Layout for Uniform Water Application (IFAS Publication Bulletin 230; on the Web at: http://edis.ifas.ufl.edu/AE084)

Irrigation System Controllers (IFAS Publication SS-AGE-22; on the Web at: http://edis.ifas.ufl.edu/AE077)

Retrofitting a Traditional In-ground Irrigation Sprinkler System for Microirrigation (IFAS Publication ABE324; on the Web at: http://edis.ifas.ufl.edu/AE222)

Abbreviations

in -- inches

gal -- gallons

hr -- hour

gpm -- gallons per minute

gph -- gallons per hour

min -- minutes

ft -- feet

ft2 -- square feet

Tables

Table 1. 

Irrigation zone run time (min) for a given application rate and a desired application depth.

Application rate

(in/hr)

Desired Application Amount

(in)

 

0.25

0.50

0.75

1.00

0.00

0

0

0

0

0.25

60

120

180

240

0.50

30

60

90

120

0.75

20

40

60

80

1.00

15

30

45

60

1.25

12

24

36

48

1.50

10

20

30

40

1.75

9

17

26

34

2.00

8

15

23

30

Table 2. 

Irrigation controller run time for each of two irrigation events per week at an application rate of 0.25 in/hr, assuming system efficiency of 60%, and considering effective rainfall*.

 

North Florida

Central Florida

South Florida

 

Percent Replacement

 

60%

80%

100%

60%

80%

100%

60%

80%

100%

Jan

0

2

0

23

31

38

57

76

94

Feb

0

2

0

17

22

28

61

80

100

Mar

10

14

17

34

46

57

85

113

141

Apr

59

79

99

81

108

134

91

121

151

May

100

134

167

128

171

214

83

110

138

Jun

90

120

150

100

133

167

75

100

126

Jul

84

112

140

97

130

162

117

156

195

Aug

77

103

129

127

169

211

129

172

215

Sep

98

131

164

95

127

159

77

102

128

Oct

64

86

107

86

115

143

31

41

51

Nov

40

54

67

64

85

106

80

106

133

Dec

16

21

26

32

43

54

71

94

118

*If the controller only allows 15 incremental changes, use the increment closest to the numbers in the table.

Table 3. 

Irrigation controller run time for each of two irrigation events per week at an application rate of 0.50 in/hr, assuming system efficiency of 60%, and considering effective rainfall*.

 

North Florida

Central Florida

South Florida

 

Percent replacement

 

60%

80%

100%

60%

80%

100%

60%

80%

100%

Jan

0

0

0

12

15

19

28

38

47

Feb

0

0

0

0

11

14

30

40

50

Mar

0

0

0

17

23

28

42

56

70

Apr

30

40

49

40

54

67

45

60

76

May

50

67

84

64

85

107

41

55

69

Jun

45

60

75

50

67

83

38

50

63

Jul

42

56

70

49

65

81

59

78

98

Aug

39

51

64

63

85

106

64

86

107

Sep

49

66

82

48

64

80

38

51

64

Oct

32

43

54

43

57

72

15

20

26

Nov

20

27

34

32

43

53

40

53

67

Dec

0

10

13

16

21

27

35

47

59

*If the controller only allows 15 incremental changes, use the increment closest to the numbers in the table.

Table 4. 

Irrigation controller run time for each of two irrigation events per week at an application rate of 0.75 in/hr, assuming system efficiency of 60%, and considering effective rainfall*.

 

North Florida

Central Florida

South Florida

 

Percent replacement

 

60%

80%

100%

60%

80%

100%

60%

80%

100%

Jan

0

0

0

0

10

13

19

25

31

Feb

0

0

0

0

0

0

20

27

33

Mar

0

0

0

11

15

19

28

38

47

Apr

20

26

33

27

36

45

30

40

50

May

33

45

56

43

57

71

28

37

46

Jun

30

40

50

33

44

56

25

33

42

Jul

28

37

47

32

43

54

39

52

65

Aug

26

34

43

42

56

70

43

57

72

Sep

33

44

55

32

42

53

26

34

43

Oct

21

29

36

29

38

48

10

14

17

Nov

13

18

22

21

28

35

27

35

44

Dec

0

0

0

11

14

18

24

31

39

*If the controller only allows 15 incremental changes, use the increment closest to the numbers in the table.

Table 5. 

Irrigation controller run time for each of two irrigation events per week at an application rate of 1.00 in/hr, assuming system efficiency of 60%, and considering effective rainfall*.

 

North Florida

Central Florida

South Florida

 

Percent replacement

 

60%

80%

100%

60%

80%

100%

60%

80%

100%

Jan

0

0

0

0

0

0

14

19

24

Feb

0

0

0

0

0

0

15

20

25

Mar

0

0

0

0

11

14

21

28

35

Apr

15

20

25

20

27

34

23

30

38

May

25

33

42

32

43

53

21

28

34

Jun

22

30

37

25

33

42

19

25

31

Jul

21

28

35

24

32

41

29

39

49

Aug

19

26

32

32

42

53

32

43

54

Sep

25

33

41

24

32

40

19

26

32

Oct

16

21

27

21

29

36

0

10

13

Nov

10

13

17

16

21

27

20

27

33

Dec

0

0

0

0

11

13

18

24

29

*If the controller only allows 15 incremental changes, use the increment closest to the numbers in the table.

Table 6. 

Irrigation controller run time for each of two irrigation events per week at an application rate of 1.25 in/hr, assuming system efficiency of 60%, and considering effective rainfall*.

 

North Florida

Central Florida

South Florida

 

Percent replacement

 

60%

80%

100%

60%

80%

100%

60%

80%

100%

Jan

0

0

0

0

0

0

11

15

19

Feb

0

0

0

0

0

0

12

16

20

Mar

0

0

0

0

0

11

17

23

28

Apr

12

16

20

16

22

27

18

24

30

May

20

27

33

26

34

43

17

22

28

Jun

18

24

30

20

27

33

15

20

25

Jul

17

22

28

19

26

32

23

31

39

Aug

15

21

26

25

34

42

26

34

43

Sep

20

26

33

19

25

32

15

20

26

Oct

13

17

21

17

23

29

0

0

10

Nov

0

11

13

13

17

21

16

21

27

Dec

0

0

0

0

0

11

14

19

24

*If the controller only allows 15 incremental changes, use the increment closest to the numbers in the table.

Table 7. 

Irrigation controller run time for each of two irrigation events per week at an application rate of 1.50 in/hr, assuming system efficiency of 60%, and considering effective rainfall*.

 

North Florida

Central Florida

South Florida

 

Percent replacement

 

60%

80%

100%

60%

80%

100%

60%

80%

100%

Jan

0

0

0

0

0

0

0

13

16

Feb

0

0

0

0

0

0

0

13

17

Mar

0

0

0

0

0

0

14

19

23

Apr

0

13

16

13

18

22

15

20

25

May

17

22

28

21

28

36

14

18

23

Jun

15

20

25

17

22

28

13

17

21

Jul

14

19

23

16

22

27

20

26

33

Aug

13

17

21

21

28

35

21

29

36

Sep

16

22

27

16

21

27

13

17

21

Oct

11

14

18

14

19

24

0

0

0

Nov

0

0

11

11

14

18

13

18

22

Dec

0

0

0

0

0

0

12

16

20

*If the controller only allows 15 incremental changes, use the increment closest to the numbers in the table.

Table 8. 

Irrigation controller run time for each of two irrigation events per week at an application rate of 1.75 in/hr, assuming system efficiency of 60%, and considering effective rainfall*.

 

North Florida

Central Florida

South Florida

 

Percent Replacement

 

60%

80%

100%

60%

80%

100%

60%

80%

100%

Jan

0

0

0

0

0

0

0

11

13

Feb

0

0

0

0

0

0

0

11

14

Mar

0

0

0

0

0

0

12

16

20

Apr

0

11

14

12

15

19

13

17

22

May

14

19

24

18

23

31

12

16

20

Jun

13

17

21

14

19

24

11

14

18

Jul

12

16

20

14

19

23

17

22

28

Aug

11

15

18

18

23

30

18

25

31

Sep

14

19

23

14

18

23

11

15

18

Oct

0

12

15

12

16

20

0

0

0

Nov

0

0

0

0

12

15

11

15

19

Dec

0

0

0

0

0

0

10

13

17

*If the controller only allows 15 incremental changes, use the increment closest to the numbers in the table.

Table 9. 

Irrigation controller run time for each of two irrigation events per week at an application rate of 2.00 in/hr, assuming system efficiency of 60%, and considering effective rainfall*.

 

North Florida

Central Florida

South Florida

 

Percent Replacement

 

60%

80%

100%

60%

80%

100%

60%

80%

100%

Jan

0

0

0

0

0

0

0

0

12

Feb

0

0

0

0

0

0

0

0

12

Mar

0

0

0

0

0

0

11

14

18

Apr

0

0

12

10

13

17

11

15

19

May

13

17

21

16

21

27

10

14

17

Jun

11

15

19

12

17

21

0

13

16

Jul

10

14

17

12

16

20

15

20

24

Aug

0

13

16

16

21

26

16

21

27

Sep

12

16

20

12

16

20

0

13

16

Oct

0

11

13

11

14

18

0

0

0

Nov

0

0

0

0

11

13

0

13

17

Dec

0

0

0

0

0

0

0

12

15

*If the controller only allows 15 incremental changes, use the increment closest to the numbers in the table.

Footnotes

1.

This document is CIR1421, one of a series of the Agricultural and Biological Engineering Department, Florida Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida. Original publication date July 2002. Revised March 2009. Reviewed January 2012. Visit the EDIS website at http://edis.ifas.ufl.edu.

2.

Michael D. Dukes, assistant professor; Dorota Z. Haman, associate professor; Agricultural and Biological Engineering Department, Institute of Food and Agricultural Sciences, University of Florida, Gainesville.

The appearance of trade names in this publication does not imply endorsement of any product by the authors or by the Institute for Food and Agricultural Sciences at the University of Florida.


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.