Subsurface drip irrigation (SDI) 1. Pump. SDI systems generally
systems provide water and nutri- have low pressure require-
ents directly to the plant root zone ments. Only one pump is
through built-in emitters on needed, as is the case for most
polyethylene tubes that are buried irrigation systems in Kansas.
below the soil surface. Experience The pressure requirement is in
in Kansas has shown that properly the range of most low-pressure
designed and managed systems can center pivot sprinkler systems.
maintain or potentially improve The size of the pump depends
yields, while saving water, fertil- on flow rate and total head
izer, energy, and money. However, requirements. The total head
these systems also require careful requirements include pumping
management to function properly. lift, friction/losses, elevation
A good first step toward maintain- changes, system pressure and,
ing a profitable SDI system is for SDI systems, the pressure
proper selection of the system loss across the filter and other
components. structural components, such as
control valves, flow meter,
This publication: check valves, main, and
1. Lists the basic components for submain supply lines.
a subsurface drip irrigation
system. • Considerations. The size of the
2. Explains the important factors pump will depend on the water
to consider in selecting com- supply capacity, system
ponents. pressure needs, zone size (area
Subsurface Figure 1 shows the basic compo-
to be irrigated at one time),
and the filter and flushline
nents of a typical SDI system and a flushing requirements.
Drip general organization of the compo-
nents. These basic components are 2. Filter system. The filter
Irrigation (SDI) required for any system. system removes suspended
particles from water to prevent
emitter clogging. A group of
filters can be installed in
An SDI system can function parallel to increase total flow
Minimum without all of the listed compo- rate. A series of filters can be
nents, but it may be difficult to used to improve filtration.
Requirements manage and maintain and may
perform poorly. Eventually, the • Options. Screens, discs, and
system may fail due to the lack of sand media filters are com-
Danny H. Rogers cues to the manager on the status of monly used depending on
Extension Agricultural Engineer performance or insufficient emitter water quality. Centrifugal sand
protection. Usually there are several separators are used when water
Freddie R. Lamm
Research Irrigation Engineer
versions of each component; these carries sand load from deep
are listed as options below. A wells. Settling basins to
Mahbub Alam specific option may or may not be remove sediment load for
Extension Agricultural Engineer acceptable for your application surface water supply system
depending on the specific site and may be required in addition to
system conditions. The major regular filter system. A combi-
factors that should be considered nation of devices may be used
when selecting each component are to remove suspended particles.
listed under considerations. Make Many of these systems have
Kansas State University sure the characteristics of your site automatic backflush capability.
Agricultural Experiment Station and system are specifically ad-
and Cooperative Extension Service dressed in your SDI system design.
• Considerations. Water quality, 3. Pressure-sustaining valve. particulates into the water
emitter requirements (maxi- Depending on the type of supply and are installed
mum allowable particle size), filtration, the unit may be between the water supply or
and system flow rate are equipped with a pressure- pump and the chemical
important filtering factors. sustaining valve to facilitate injection line.
Water quality relates to the flushing (automatic or manual).
amount, size, and type of • Options. A physical air gap
particles (organic or mineral) 4. Pressure gauges. The filter(s) between waterline and
to be removed. For example, should have pressure gauges at fertigation tank, an atmo-
surface water typically has the inlet and outlet points to spheric vacuum breaker, a
much higher organic matter show pressure differential for pressure vacuum breaker, or a
content than groundwater, initiating flushing of the double-check valve are options
which affects the type of filter filtration unit, either manually to prevent backflow.
that can be used. Filtration or automatically. Follow the
requirement is determined by manufacturer’s recommenda- • Considerations. The type of
the emitter size or opening. tion on the pressure differential fluid that can backflow (toxic
That information is provided value at which flushing should or nontoxic), and whether
by the manufacturer and must be initiated. It also is recom- there can be back pressure or
be followed to help ensure mended to have pressure back siphonage are important
system longevity. In general, gauges at the beginning of the considerations. State and local
filtration is provided to prevent main delivery system and at regulations and codes must be
passing of particles 1⁄10 the size the distal end of the system followed.
of the smallest passageway. fitted on flushline. The flow
Primary filters are grouped as rate from the meter and the 6. Regulation valve. These
screen, disc, or media filters. pressure reading of the system valves are used to help main-
K-State Research and Exten- provide cues to the operator tain the proper pressure in
sion publication, MF-2361, about emitter performance and irrigation lines.
Filtration and Maintenance clogging.
Considerations for Subsurface • Considerations. The
Drip Irrigation (SDI) Systems, 5. Backflow preventer. These manufacturer’s emitter rating
discusses filtration needs in devices prevent the backflow and the pipeline pressure
more detail. of fertilizers, chemicals, or losses during the delivery of
Figure 1. Schematic of Subsurface Drip Irrigation (SDI) System. (Components are not to scale.)
Flowmeter Backflow Pump
Main Line Injection
Air & Vacuum
1 and 2 Pressure Gauge
the water to the dripline chemical supply tank in case water from the system head-
connection point are important of injector failure. This valve works control to manifolds
considerations. Emitters are is often an integral part of an connecting dripline laterals.
typically rated by manufactur- injector unit and can handle
ers to provide a specific flow both backpressure and • Considerations. System
rate if operated at a given backsiphonage. pressure, required flow rates,
pressure. The regulation valve water hammer, and pipe cost
must be sized to provide this • Considerations. State and local are the consideration factors
pressure while accounting for codes must be followed. for consideration.
pressure losses that occur
between the valve and the 10. Zone valve. These valves are 14. Flushlines. The flushlines at
emitter. opened or closed to control the the tail end of the system serve
flow to appropriate zones. three purposes:
7. Chemical injector. A chemical They can be automatically 1) Allow any sediment and
injector precisely injects controlled using an electronic contaminants to be flushed
fertilizers or pesticides into the control system. In production from dripline laterals at a
irrigation stream. agriculture, these zone valves centralized location,
are often manually operated 2) Equalization of pressure in
• Options. There are two types where the zone size is appre- the dripline laterals, and
of chemical injection units: ciably large. 3) Allow positive pressure on
1) Constant rate (positive both sides of a dripline break
displacement): diaphragm, 11. Pressure regulator. Pressure to prevent soil ingestion into
piston, or gear pumps and regulators are typically located the dripline.
2) Variable rate: venturi on the manifold to help
pressure differential injectors regulate operating pressure for 15. Header manifold. The header
or bladder tanks. emitters. manifold delivers water from the
submain to the laterals and links
• Considerations. The types of • Considerations. Manufacturer a number of driplines together
chemicals used, rate of injec- emitter rating and line pressure into one controllable unit. In
tion, method of injection, and losses are the major consider- most agricultural fields, the
the precision required are ations. Emitters are typically submain serves this function.
determining factors in selec- rated by manufacturers to
tion of the best type of injector. provide a specific flow rate if 16. Dripline. The dripline is the
The required number of operated at a given pressure. polyethylene tubing that
injection systems and their The pressure regulator must be includes a built-in emitter.
injection point location depend sized to provide this pressure Emitter spacing and rate are
on the clogging hazard and/or while accounting for pressure selected to match crop de-
the material being injected. losses that occur between the mands and soil water-holding
regulator and the emitters. capacity. They must be com-
8. Flowmeter. The flowmeter patible with the pumping
measures the volume of water 12. Air and vacuum release pressure and flow capacity.
moving through the system, valves. These valves prevent Driplines are available in a
either as a flowrate or as an soil or particulate material from variety of wall thicknesses,
accumulated total volume being sucked back into emitters diameters, emitter spacings,
basis. The flowmeter provides when the irrigation system is and flow rates. Most SDI
the operator with information turned off or when driplines are systems in Kansas use
on how the system is perform- drained. They cannot handle driplines with 8 (0.250 mm) to
ing and how to schedule the backpressure, only back- 15 (0.375 mm) MIL wall
water application. siphonage. All high elevation thickness. SDI systems for row
points of system should have crops tend to use large diam-
9. Chemigation line check air or vacuum relief. eter (7/8 inch or greater diam-
valve. This valve, installed eter), thin-walled and low-flow
between the injector and the 13. Main line, submain. The main driplines, which are sometimes
water source, prevents line and submains are the referred to as driptapes. Larger
backflow of water into the delivery pipelines that supply diameter and lower flows
allow longer length of runs and dripline connection or may to minimize initial investment
larger zone size that are receive a supply tube that is costs whenever possible is a
appropriate for the typical field attached to the dripline. The practical goal. However, cost
sizes in Kansas. Pressure- dripline connector options are reductions should be attempted
compensating driplines are wired, clamped, or interference only if system design and operat-
available, but are generally not (compression) fit. ing integrity are not compromised.
used in Kansas due to higher Cost cutting that results in a poor
cost. Water quality also may be Optional Automatic design or a difficult to manage
a consideration in the choice of System Control system may increase operating
emitter size and spacing to Automatic control may be costs, decrease system perfor-
avoid clogging. K-State useful for precise delivery of water mance and increase the chance of
Research and Extension and nutrients according to design system failure.
publication, MF-2578, Design or crop need. This also reduces the
Considerations for SDI need for manual control. Additional Resources
Systems, discuss these consid- MF-2361 Filtration and Mainte-
erations in more detail. Automatic controls. Pumps, nance Considerations for Subsur-
valves, and injectors can be turned face Drip Irrigation (SDI) Systems
• Considerations. Tubing wall on and off or opened and closed to MF-2242 Economic Compari-
thickness, emitter spacing, allow automatic timing and son of SDI and Center Pivots for
discharge rate, soil texture, and sequencing of irrigation zones. Various Field Sizes
soil water holding capacity are These may be linked to automatic MF-836 Irrigation Capital
considerations because these timers, soil water sensors, or Requirements and Energy Cost
affect plant root zone water weather-based models to determine MF-2578 Design Considerations
content and distribution. when irrigation system should run. for Subsurface Drip Irrigation
Computer control and monitoring MF-2590 Management Consid-
18. Connectors. Connectors are is an option, but not required for eration for Operating a Subsurface
needed to attach the dripline to automation. Drip Irrigation System
the manifold or submain. The MF-2575 Water Quality Assess-
number and type depend on Summary ment Guidelines for Subsurface
system layout. There are many SDI systems have higher initial Drip Irrigation
types of connectors. Connector investment costs compared to
options include glued, grom- traditional types of irrigation K-State Research and Extension
met, barb, and compression. systems used in Kansas, so efforts SDI Web site
These can have a direct www.oznet.ksu.edu/sdi
Acknowledgment: This material is based upon work supported by the U.S. Department of Agriculture Cooperative State Research Service
under Agreement No. 00-34296-9154. Any opinions, findings, conclusions or recommendations expressed in this publication are those of
the authors and do no necessarily reflect the views of the U.S. Department of Agriculture.
Brand names appearing in this publication are for product identification purposes only. No endorsement is intended,
nor is criticism implied of similar products not mentioned.
Publications from Kansas State University are available on the World Wide Web at: http://www.oznet.ksu.edu
Contents of this publication may be freely reproduced for educational purposes. All other rights reserved.
In each case credit Danny H. Rogers et al., Subsurface Drip Irrigation (SDI) Components: Minimum Requirements,
Kansas State University, July 2003.
Kansas State University Agricultural Experiment Station and Cooperative Extension Service
MF-2576 July 2003
It is the policy of Kansas State University Agricultural Experiment Station and Cooperative Extension Service that all persons shall have equal opportunity and
access to its educational programs, services, activities, and materials without regard to race, color, religion, national origin, sex, age or disability. Kansas State
University is an equal opportunity organization. Issued in furtherance of Cooperative Extension Work, Acts of May 8 and June 30, 1914, as amended. Kansas
State University, County Extension Councils, Extension Districts, and United States Department of Agriculture Cooperating, Marc A. Johnson, Director.