Trickle Irrigation for Home Gardens
AE-889, Reviewed and reprinted March 1995
Wayne E. Burbank, Area Extension Irrigation Agent
Ron Meyer, Irrigationist, Carrington Irrigation Station
Robert Hoffman, Former Engineer, Carrington Irrigation Station
Introduction
Water Requirements
Connecting the Water Supply to Trickle Irrigation System
Submains and Zoning
Emitters and Microtubes
Dew Hose
Twin-Wall Tube
Alternate Water Supply
Area Requirement and Row Spacing
Automation
Maintenance
Extended periods of dry weather may appreciably reduce the yield potential of a home
garden. If good quality water for irrigation is not available, a much larger dryland area
may be needed to obtain the desired production. Trickle irrigation may be the answer for
those home gardeners who do not have sufficient good quality water for sprinkler
irrigation.
Trickle irrigation involves frequent applications of small amounts of water directly to
the root area of the plants. Water is applied under low pressure and irrigations are
accomplished with considerable reduction in total water usage. With trickle irrigation,
only a small area immediately around each plant is wetted, leaving the remaining soil
surface dry. Weed control is more easily maintained because weed seeds are discouraged
from germinating in the dry soil.
Foliage (leaf diseases are less apt to develop under trickle irrigation since plant
leaves are not wetted as with sprinkler irrigation. Free water on plant leaves is a
necessary ingredient for growth and development of many foliar diseases. In addition,
chemicals applied for disease and insect control are not washed from the plants except
when rainfall is received.
Providing the water quality is satisfactory for irrigation, the water requirements of
the average home garden can be easily supplied from the faucet of a home water supply. The
quantity needed will vary with climatic conditions and growth state of the vegetable crop.
Water Requirements
Water conservation is the primary reason for considering trickle irrigation. On the
average, trickle irrigation will reduce the water required to less than one-half of the
gallonage used with sprinkler irrigation, as shown in Table 1.
Table 1. Water Consumption Comparing Trickle vs. Sprinkler Irrigation
------------------------------------------------------
Water Required
(in gallons) Water
when Losses
Area of Soil 1" of water Through
Type of Wetted When is applied on Evaporation
Irrigation Irrigated 1,000 sq. ft. or Drift
------------------------------------------------------
Trickle 50% or less 300 gallons Very Little
Sprinkler 100% 625 gallons 15-20% Lost
------------------------------------------------------
Considerably less water is required because the entire soil surface is not wetted during
trickle irrigation; water is applied directly to the base of the growing plant. Assuming
one-half or less of the soil is wetted, a 1-inch application on a 1,000-square-foot area
of garden would require 300 gallons of water. A 1-inch application to a 1,000-square-foot
area of a garden with an overhead sprinkler system would require 625 gallons.
Approximately 100 gallons or more of that 625 gallons would be lost to evaporation or
drift as the water travels through the air. This would leave .80 to .85 inch of that 1
inch available for plant use. Losses to evaporation or drift can be much higher during
hot, windy conditions with sprinkler irrigation .
Connecting the Water Supply to Trickle Irrigation System
A mainline runs from the water source and delivers water to the garden site. One-half
or 1-inch black polyethylene pipe is an excellent water delivery source to use for this
purpose. See Tables 4, 5, 6, and 7 for selection of mainline size. It is advisable to
select good quality pipe which is resistant to deterioration from exposure to sunlight. A
short piece of garden hose with a female faucet fitting on one end and a plastic coupler
on the other can be used to connect the faucet to the mainline.
To eliminate damage from lawnmowers and other equipment, the mainline may be buried.
This can be done easily by cutting a narrow trench with a spade and burying the pipe 2 to
4 inches deep.
Since water emitters will plug easily, water quality must be watched. The water used
for irrigation must be kept sand and silt free or filtration must be provided. A 100-mesh
screen water filter may be installed directly in the mainline. This will adequately filter
out any trouble-causing particles.
At the garden edge, a flow regulating valve or a pressure regulator should be installed
(Figure 1). This valve or pressure regulator is especially important because it controls
the operating pressure of the system. An accurate pressure gauge should be installed
downstream of the regulating valve in order to set operating pressure. It may be desirable
to install a bypass around the pressure regulator for easy flushing of laterals and to
allow quick filling of a zone or zones so all air is removed and emitters operate
properly. Farm water systems generally operate at an average of 40 pounds per square inch
(psi) where a drip system will operate successfully at 2� to 5 psi. Once the system is
full of water, simply adjust the valve to obtain the desired cut in pressure. A pressure
regulator will automatically maintain the preset pressure. If a hand controlled regulating
valve is used, pressure will fluctuate, depending on water use on the supply system. If a
pressurized farm water system is not available, an elevated tank may be used as a water
source (Figure 2--alternate water supply). The operating pressure is dependent on the
height of the tank. For each 1 psi desired, elevate the tank 2.31 feet. A pressure gauge
may be installed directly behind the gate valve to monitor the operating pressure.
Figure 1. Typical Trickle Irrigation
Layout Using Zones and a Pressure Water Supply (12KB b&w
diagram)
Figure 2. Elevated
Water Supply (7KB b&w diagram)
Row lateral pipe size will depend on the lateral length, the kind of emitters used and
the spacing along the lateral. Guidelines for determining lateral size are found in Tables
2 and 3. Laterals should be sized so there is not more than a 10 percent difference in
discharge between the first and last emitter on the line or zone. The discharge should not
vary more than 10 percent if the pressure difference from the first to the last emitter
varies 20 percent or less.
Guidelines for selecting pipe for mains and submains are given in Tables 4, 5, 6, and
7. It is recommended that the total pressure loss should be divided between the submain
and the laterals.
Table 2. Maximum Lateral Lengths 1 Gallon Per Hour Emitter Flow Rate
Pressure Loss (PSI) for Laterals
------------------------------------------------------------------
Emitter
Spacing 1 ft. 1.5 ft. 2 ft.
----------------- ----------------- -----------------
Nominal
Pipe
Diameter
in Inches 3/8 1/2 3/4 3/8 1/2 3/4 3/8 1/2 3/4
------------------------------------------------------------------
Length of
Lateral
in Feet:
25 .25 .02 .00 .10 .01 .00 .06 .00 .00
50 1.57 .97 .02 .65 .04 .01 .31 .03 .00
75 4.79 .30 .07 1.99 .13 .03 1.09 .08 .02
100 .65 .16 4.39 .30 .07 2.40 .17 .04
150 2.00 .48 .91 .23 7.33 .53 .13
200 4.41 1.07 2.00 .50 1.16 .29
250 1.97 3.69 .92 2.14 .54
300 3.26 6.00 1.51 3.53 .90
350 4.98 2.31 5.40 1.36
400 3.34 1.96
450 4.62 2.71
500 3.62
550 4.71
600
650
700
------------------------------------------------------------------
-------------------(continued)------------------
Emitter
Spacing 2.5 ft. 3 ft.
----------------- -----------------
Nominal
Pipe
Diameter
in Inches 3/8 1/2 3/4 3/8 1/2 3/4
-----------------------------------------------
Length of
Lateral
in Feet:
25 .04 .00 .00 .03 .00 .00
50 .25 .02 .00 .17 .01 .00
75 .69 .05 .01 .52 .04 .01
100 1.52 .11 .03 1.06 .08 .02
150 4.65 .35 .09 3.23 .25 .06
200 10.26 .76 .19 7.13 .55 .14
250 1.42 .36 1.01 .26
300 2.33 .59 1.66 .42
350 3.56 .90 2.54 .65
400 5.14 1.30 3.67 .93
450 1.80 5.70 1.29
500 2.40 1.73
550 3.13 2.24
600 3.97 2.85
650 3.55
700 4.36
-----------------------------------------------
Table 3. Maximum Lateral Lengths 2 Gallons Per Hour Emitter Flow Rate Pressure
Loss (PSI) for Laterals
-----------------------------------------------------------------
Emitter
Spacing 1 ft. 1.5 ft. 2 ft.
----------------- ----------------- ----------------
Nominal
Pipe
Diameter
in Inches 3/8 1/2 3/4 3/8 1/2 3/4 3/8 1/2 3/4
-----------------------------------------------------------------
Length of
Lateral
in Feet:
25 .85 .05 .01 .35 .02 .00 .19 .01 .00
50 5.29 .33 .08 2.19 .15 .04 1.30 .09 .02
75 1.00 .24 6.69 .45 .11 3.66 .26 .07
100 2.20 .53 1.01 .25 8.08 .58 .15
150 6.72 1.63 3.05 .76 1.27 .44
200 3.60 6.73 1.68 3.90 .98
250 6.64 3.09 7.20 1.81
300 5.09 2.99
400 7.78 4.57
450 6.59
500
550
600
650
700
-----------------------------------------------------------------
------------------(continued)------------------
Emitter
Spacing 2.5 ft. 3 ft.
----------------- -----------------
Nominal
Pipe
Diameter
in Inches 3/8 1/2 3/4 3/8 1/2 3/4
-----------------------------------------------
Length of
Lateral
in Feet:
25 .14 .01 .00 .09 .01 .00
50 .83 .06 .02 .57 .04 .01
75 2.32 .17 .04 1.75 .13 .03
100 5.13 .38 .10 3.56 .27 .07
150 15.64 1.16 .30 10.86 .83 .21
200 2.57 .65 1.83 .47
250 4.74 1.20 3.39 .86
300 7.83 1.99 5.59 1.43
400 3.03 8.54 2.18
450 4.38 3.14
500 6.06 4.35
550 5.80
600
650
700
-----------------------------------------------
Table 4. Main and Submain Lengths Pressure Loss (PSI) for Mains and Submains Pipe
Size 3/8 Inch
--------------------------------------------------------------------------
Flow Rate GPH 25 50 75 100 150 200 250
Flow Rate GPM (.41) (.83) (1.25) (1.66) (2.50) (3.33) (14.16)
--------------------------------------------------------------------------
Pipe Length
In Feet:
3 .05 .18 .36 .60 1.23 2.03 3.00
6 .09 .32 .65 1.07 2.17 3.59 5.31
9 .14 .46 .93 1.53 3.12 5.15
12 .18 .59 1.21 2.00 4.06
15 .22 .73 1.49 2.46
20 .29 .96 1.96 3.24
25 .35 1.19 2.42 4.01
50 .70 2.34 4.76
75 1.04 3.49
100 1.38 4.64
150 2.06
200 2.75
250 3.43
300 4.12
350
400
-----------------------------(continued)---------------------------------
Flow Rate GPH 300 350 400
Flow Rate GPM (5.00) (5.83) (6.66)
-----------------------------------------
Pipe Length
In Feet:
3 4.13
6
9
12
15
20
25
50
75
100
150
200
250
300
350
400
--------------------------------------------------------------------------
Table 5. Main and Submain Lengths Pressure Loss (PSI) for Mains and
Submains Pipe Size 1/2 Inch
--------------------------------------------------------------------------
Flow Rate GPH 75 100 150 200 250 300 350
Flow Rate GPM (1.25) (1.66) (2.50) (3.33) (4.16) (5.00) (5.83)
--------------------------------------------------------------------------
Pipe Length
In Feet:
3 .03 .05 .09 .16 .23 .32 .41
6 .05 .09 .18 .30 .44 .60 .79
9 .08 .13 .26 .44 .65 .89 1.17
12 .10 .17 .35 .58 .86 1.18 1.54
15 .13 .21 .44 .72 1.06 1.46 1.92
20 .17 .28 .58 .96 1.41 1.94 2.54
25 .21 .35 .72 1.19 1.72 2.42 3.17
50 .43 .70 1.43 2.37 3.49 4.81 6.30
75 .64 1.05 2.14 3.54 5.24
100 .85 1.40 2.85 4.72
150 1.27 2.10 4.28
200 1.69 2.80
250 2.12 3.50
300 2.54 4.20
350 2.96
400 3.39
----------------------------(continued)-----------------------------------
Flow Rate GPH 400 450 500 550 600 650 700
Flow Rate GPM (6.66) (7.50) (8.33) (9.16) (10.00) (10.83) (11.66)
--------------------------------------------------------------------------
Pipe Length
In Feet:
3 .52 .64 .77 .91 1.06 1.22 1.39
6 1.00 1.23 1.47 1.74 2.03 2.33 2.66
9 1.47 1.81 2.18 2.57 2.99 3.44 3.92
12 1.95 2.39 2.88 3.40 3.96
15 2.42 2.98 3.58 4.23
20 3.21 3.95
25 4.01
50
75
100
150
200
250
300
350
400
--------------------------------------------------------------------------
Table 6. Main and Submain Lengths Pressure Loss (PSI) for Mains and
Submains Pipe Size 3/4 Inch
--------------------------------------------------------------------------
Flow Rate GPH 200 250 300 350 400 450 500
Flow Rate GPM (3.33) (4.16) (5.00) (5.83) (6.66) (7.50) (8.33)
--------------------------------------------------------------------------
Pipe Length
In Feet:
3 .04 .06 .08 .11 .13 .16 .20
6 .08 .11 .16 .20 .26 .32 .38
9 .11 .17 .23 .30 .38 .47 .57
12 .15 .22 .31 .40 .51 .62 .75
15 .19 .28 .38 .50 .63 .78 .93
20 .25 .37 .51 .67 .84 1.03 1.24
25 .31 .46 .63 .83 1.05 1.29 1.55
50 .62 .92 1.26 1.65 2.09 2.57 3.09
75 .93 1.38 1.89 2.48 3.13 3.85 4.63
100 1.24 1.83 2.52 3.30 4.17 5.13
150 1.86 2.75 3.78 4.95
200 2.48 3.66 5.04
250 3.10 4.58
300 3.71
350 4.33
--------------------------(continued)-------------------------------------
Flow Rate GPH 600 700 800 900 1000 1100
Flow Rate GPM (10.00) (11.66) (13.33) (15.00) (16.66) (18.33)
--------------------------------------------------------------------------
Pipe Length
In Feet:
3 .27 .35 .44 .55 .66 .78
6 .52 .69 .87 1.07 1.28 1.52
9 .78 1.02 1.29 1.58 1.90 2.25
12 1.03 1.35 1.71 2.10 2.52 2.98
15 1.29 1.68 2.13 2.62 3.14 3.72
20 1.71 2.24 2.83 3.48 4.18
25 2.13 2.79 3.53 4.34
50 4.25 5.56
75
100
150
200
250
300
350
--------------------------------------------------------------------------
Table 7. Main and Submain Lengths Pressure Loss (PSI) for Mains and
Submains Pipe Size 1 Inch
--------------------------------------------------------------------------
Flow Rate GPH 500 550 600 650 700 750
Flow Rate GPM (8.33) (9.16) (10.00) (10.83) (11.66) (12.50)
--------------------------------------------------------------------------
Pipe Length
In Feet:
3 .06 .07 .08 .09 .11 .12
6 .12 .14 .16 .19 .21 .24
9 .18 .21 .24 .28 .32 .36
12 .23 .28 .32 .37 .42 .48
15 .29 .35 .40 .46 .53 .60
20 .39 .46 .54 .62 .70 .79
25 .49 .58 .67 .77 .88 .99
50 .98 1.15 1.34 1.55 1.76 1.99
100 1.47 1.73 2.02 2.32 2.64 2.98
150 1.95 2.31 2.69 3.09 3.52 3.97
200 2.93 3.46 4.03 4.64 5.28
250 3.90 4.62
300 4.88
----------------------------(continued)-----------------------------------
Flow Rate GPH 800 850 900 1000 1100 1200
Flow Rate GPM (13.33) (14.16) (15.00) (16.66) (18.33) (20.00)
--------------------------------------------------------------------------
Pipe Length
In Feet:
3 .13 .15 .16 .20 .23 .27
6 .27 .30 .33 .39 .47 .54
9 .40 .46 .49 .59 .70 .81
12 .53 .59 .66 .79 .93 1.09
15 .67 .74 .82 .99 1.64 1.36
20 .89 .99 1.09 1.31 1.55 1.81
25 1.11 1.28 1.37 1.64 1.94 2.26
50 2.22 2.47 2.73 3.28 3.88 4.52
100 3.34 3.70 4.10 6.57
150 4.45 4.94
200
250
300
----------------------------(continued)-----------------------------------
Flow Rate GPH 1300 1400 1500 1600 1700 1800
Flow Rate GPM (21.66) (23.33) (25.00) (26.66) (28.33) (30.00)
--------------------------------------------------------------------------
Pipe Length
In Feet:
3 .31 .36 .40 .45 .50 .55
6 .62 .71 .80 .90 1.00 1.10
9 .94 1.07 1.20 1.35 1.50 1.65
12 1.25 1.42 1.60 1.80 2.00 2.21
15 1.56 1.78 2.00 2.24 2.50 2.76
20 2.08 2.37 2.67 2.99 3.33 3.68
25 2.60 2.96 3.34 3.74
50 5.20 5.92
100
150
200
250
300
----------------------------(continued)-----------------------------------
Flow Rate GPH 1900 2000 2100 2200
Flow Rate GPM (31.66) (33.33) (35.00) (36.66)
--------------------------------------------------------------------------
Pipe Length
In Feet:
3 .61 .66 .72 .78
6 1.21 1.33 1.44 1.57
9 1.82 1.99 2.17 2.35
12 2.42 2.65 2.89 3.13
15 3.03 3.32 3.61
20
25
50
100
150
200
250
300
--------------------------------------------------------------------------
Example:
Select the lateral and submain for a zone consisting of:
Pressure at submain = 5 psi
Length of laterals = 50 ft.
Number of laterals = 9
Distance between laterals = 3 ft.
Emitter discharge rate = 2 gph
Emitter spacing on lateral = 1.5 ft.
Submain connects to zone submain at center lateral
Allowable pressure loss
(5 psi x 20 percent allowable psi loss) = 1.0 psi
Gallons per hour each lateral = 66 gph
50 ft.
--------- = 33 emitters x 2 ghp = 66 gph
1.5 ft.
Gallons per hour for zone = 594 gph
66/lateral x 9 laterals = 594 gph
Lateral size selected (Table 3) = 1/2 inch
Lateral pressure loss (Table 3) = .15 psi
Submain size (Table 5) = 1/2 inch
Submain consists of four 36-inch pipes
either side of the point at which it is
connected to the mainline.
Gallons per hour into each 1/2 of submain = 264 gph
594 gph - 66 gph center lateral
--------------------------------- = 264 gph
2
Pressure loss in submain = .60 psi
From Table 5
PSI loss first 3 feet of submain = .32 psi
264 GPH (used 300 gph loss)
PSI loss second 3 feet of submain = .16 psi
264 - 66 = 198 gph (used 200 gph loss)
PSI loss third 3 feet of submain = .09 psi
198 - 66 = 132 gph (used 150 gph loss)
PSI loss fourth 3 feet of submain = .03 psi
132 - 66 = 66 gph (used 75 gph loss)
Total PSI loss submain = .60 psi
Plus PSI loss lateral = .15 psi
Total pressure loss in submain and lateral = .75 psi
For special drip emitters follow the manufacturers instructions for design and size of
laterals and submains.
From the mainline, the proper size black plastic pipe is continued across the garden as
a submain. Lateral lines are then tied into the submain at the desired row spacing. The
submain should be sized so submain and lateral pressure loss does not exceed the maximum
allowed. Each lateral may supply water for one or two rows. When irrigating two rows per
lateral, row spacing should not exceed 10 inches. The ends of the laterals may either be
capped or plugged with dowels, or laterals may be connected at both ends.
Emitters, or any outlet device that delivers water to the crop, are placed along the
lateral lines. Black plastic pipe will stretch when warm and contract when cool, so if the
lateral is 25-30 feet or more in length, it should be cool when emitters are placed for
hilled or spaced crops. This can be accomplished by filling the system with water before
installing emitters to insure that the water will be applied where it is needed.
Zoning vegetables of like water requirements and season length will additionally aid in
water conservation. Simply place a valve between the zoned areas in the submain line, and
when a particular area no longer needs irrigating, close the valve to that zone.
Emitters are installed along the lateral lines and should be spaced between 16 and 18
inches for solid seeded rows or they may be installed at individual hills for spaced
crops. They come in many sizes and are color coded as to their output. They may also have
single or multiple outlets and are manufactured and sold by a number of companies.
One-to-two gallon-per-hour emitters are generally recommended for home garden use. Some
problems with plugging may be encountered with emitters if the water is high in soluble
salts or iron. Filtering will ease this problem.
Microtubes are long spaghetti-shaped tubes used to direct the application of water away
from the hose to an individual hill or plant. They are very popular for irrigating distant
spaced plants. Microtubes are cut to length to control the amount of water emitted. The
shorter the length of the microtube, the higher the application of irrigation water per
tube.
Dew hose may be either sewn plastic film, where drops of water are emitted through the
seam, or it may be a porous material formed into a tube that emits water droplets along
the entire surface. Dew hose works both on the surface or subsurface. However, it appears
to work best if covered with some soil. To reduce the effects a hard wind might have on
this light material, it is advisable to cover it slightly with soil. Dew hose is quite
susceptible to plugging from iron bacteria activity.
Twin-wall tube is molded from plastic and is a tube within a tube. Water seeps from the
inside tube to the outside tube and is then released to the crop. Spacing of openings from
outer tubes can vary from as close as 4 inches to more than 18 inches. The spacing should
be specified when ordering. Twinwall tube is also subject to clogging from iron bacteria.
An elevated tank may be used as a water source (Figure 2). The
size of the water supply should be sufficient to make one complete irrigation of the
garden. (A rule of thumb: About 300 gallons will trickle irrigate a 1,000 square-foot area
with 1 inch of water, assuming only one-half of the area is wetted.)
To obtain the desired pressure, elevate the base of the water tank or pressure control
box 2.31 feet for every pound per square inch required.
An alternative to an elevated tank could be ground level storage or cistern with a low
pressure pump to provide the minimum pressure of 3 to 5 pounds per square inch.
Area Requirement and Row Spacing
If the garden area is limited, considerably greater production can be obtained by using
trickle irrigation. Since the water needs of the crop are being supplied, the area between
rows need only be wide enough to accommodate plant growth and harvest. A little
experimentation will allow you to determine the best spacing for your situation.
A trickle irrigation system lends itself to automation quite easily. It may be as
simple as a time clock and solenoid valve to shut the system off to the point of turning
the system on and off as well as regulating the irrigation of each different zone. Using a
time clock to automate a drip system is convenient for daily use.
Before irrigating for the first time each year, the system should be flushed to clean
any accumulated dirt or rust out of the pipes. This can be done by removing the end caps
to each lateral or by removing a portion of the end header line, depending on which method
of capping is used, and turning on the water.
Maintenance of a drip system mainly involves keeping the emitters working properly. If
an emitter should become plugged, remove it and replace it with a spare. Soaking the
plugged emitter in water a short time will usually loosen the material inside the emitter
orifice. Blowing air through the emitter orifice will sometimes also free the passageway
and the emitter will work as good as new.
If water quality is a problem, the water filter screen will also have to be inspected
periodically. Some water filters are designed for easy removal of the screen for cleaning
purposes.
At the end of the irrigation season the drip system should be gathered and placed
inside for the winter. This will protect the plastic pipe from rodent damage and also will
help keep dirt out of the emitters. Black plastic electricians' tape can be wrapped around
the pipe at intervals to keep it gathered for winter storage.
AE-889, Reviewed and reprinted March 1995
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