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Drip System fundamentals
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Bulletin #TP2905 |
Horticultural Observations for Healthier Landscapes |
Drip Irrigation is a very practical solution towards water saving
and water efficiency
For some it may have the ominous sound of one more overly-complicated home improvement
project.
Actually using drip irrigation not only saves water but is healthier for
plants, and easy to install in a new yard. Most often it is not difficult
to convert from an existing sprinkler system to drip.
What Is Drip Irrigation? The fundamental difference between drip irrigation
and other traditional home irrigation systems is avoiding the evaporation from sprinkler mist,
and providing an opportunity to put the moisture only where it is needed, and
deep enough to reduce evaporation. The hardware it uses
reflects this approach. The appearance of wet surface soil does NOT
mean adequate water has been provided.
☞ Traditional Irrigation Systems
☞ Converting Standard System to Drip
☞ Installation [initial or conversion]
☞ Drip Irrigation Systems - SUMMARY
TRADITIONAL IRRIGATION SYSTEMS
In traditional irrigation, supply pipes are used to convey water under
pressure to outlet heads of various types. These then spray or bubble as required to a designated area of the landscape.
The sprinklers or sprays generally cover a reasonably large area and feed water
at a fairly fast rate (8 to 24 gallons per minute typical).
Because of the high feed rate, the run time is short. When using this technique on
soils with fairly slow hydraulic conductivity (moisture permeation less than 0.3 gallons per hour per square foot),
the result is that this water spreads out and runs off - rather than soaking deeply into the soil.
In drip irrigation, smaller tubing delivers a slower amount of water at a
controlled rate directly to the root zone of the plants being irrigated.
This allows an accurate zone of moist soil, both peripherally and depth.
The result is less water with healthier plants.
In most cases, drip technology can be used in an existing landscape to water trees, shrubs, flower
beds, vegetables and container plants without requiring extensive system
overhauls.
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Drip systems water at a
slow rate at any single point and should be scheduled to run less often
yet for longer periods of
time (sometimes as little as twice a month, depending on the type of
landscape and its maturity).
Drip is rated in GPH (gallons per hour), as
opposed to the GPM (gallons per minute) of traditional sprinkler heads. The
basic cycle of drip irrigation is the alternation between soil saturation and a
"resting" period when the oxygen necessary for good root growth can
infiltrate the soil. Running a drip system every day not only defeats the
purpose of the system, but may eventually result in the death of plants from
oxygen deprivation and excessive build up of salts in the soil.
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Different
soil types
absorb water at different rates. This is known as Hydraulic Conductivity Rate [HCR].
Heavy clay soils, common in the southwest, are slow to
absorb water, but are also slow to release it.
Due to the extreme difference in [HCR] it is wise to do a soil settlement test
Click Here
for Information on performing this test.
Ideal Soil Composition 0.15 to 0.89 inch per hour [HCR].
When soil accepts moisture at a rate in this range, it is easier to match
water application rate to the soil. When this occurs, moisture penetrates to
optimum depths (around 12 inches for drought prone areas), and holds moisture
long enough to help the plant avoid drought stress.
Watering frequencies are typically 3 to 4 days per week in the summer, 2 days
in the sping and fall, with 1 day a week in the winter being sufficient.
Matching the soil rate to the application rate is still the goal.
Moderately Slow Soil 0.07 to 0.14 inch per hour [HCR].
Care is required when choosing the water application rate when watering these soils.
Feed water too fast, and moisture will be shallow & evaporation will be high.
Feed water too often (frequency), irrigations per week, and plant root systems will
not have suffucuent time to breathe (respiration).
Moderately Fast Soil 0.90 to 2.50 inch per hour [HCR].
The focus of care required when choosing the water application rate when watering these soils
is feeding water fast enough to allow for proper spread and distribution.
Moisture distribution needs to be relatively even throughout the intended
root zone area.
In addition, these soils dry out quicker, so the frequency per week may need to be more.
, or the plant will wilt as the root systems suffer drought.
Very Slow Soil 0.01 to 0.07 inch per hour [HCR].
Extra Care is required when applying water to these soils.
It is usually difficult to get moisture deeper than 2 to 3 inches.
A technique that can help with this is splitting the start times; running
3 times during a watering day for 15 minutes each (instead of 1 time for 45 minutes).
Spreading the start times apart by at least 2 hours is needed to gain benefit.
How often to apply water for this soil is tricky. Because moisture will be more shallow,
evaportion is high and so the plant can reaching the wilting point more quickly.
Plant root systems still need the time to respire, so finding and
maintaining a good soil moisture balance is difficult.
The Garden Galaxy Soil-Flow Pro-I Calculator provides the accuracy required
in order to "Match" the soil and irrigation applicate rates for tough soils.
Very Fast Soil 2.50 to 7.70 inch per hour [HCR].
Extra Care is also required when applying water to these soils.
Sandy soils like this are also found in drought prone regions, and are
much quicker to both accept and give up water. These soils must be watered
more often, while the run time needs to correspond to getting moisture down to about 12 inches.
The water needs of your chosen plants also factor in
system design, so it's important to know both the type of soil you will be
irrigating and the watering requirements of the plant material.
The GG Soil-Flow Pro-I provides the accuracy required
in order to "Match" the soil and irrigation applicate rates for really sandy soils.
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Choosing Emitters
is the method for setting the water application rate. One can choose
higher rate application emitters (4 to 15 gph), or use more standard 1 gph emitters.
The only practical way to utilze a higher quantity of 1 gph emitters is through
the use of Dripperline. Click for information on Dripperlines.
To convert, remove
existing sprinkler heads or shrub adapter heads in your planted area and
install drip adapters on the risers.
These will allow you to run 0.25" flexible distribution tubing to the targeted area.
Converting:
Option # 2
Drip System Summary
With a Drip System; "Drip Emitters" feed the various areas that are watered,
and these emitters "drip" - they don't spray. This Bulletin discusses
water efficient and plant beneficial - deep watering. This deep water
is the basic and primary goal of Drip Irrigation.
Proper distribution of moisture is another very important aspect of emitter type selection.
We need the water to spread as evenly as practical throughout the root zone area.
Click here for information on Drip spacing and pacement.
We DON'T want this for a moisture profile
water depth is excessive
We also DON'T want this moisture profile
water depth is shallow
Ultimately this is what we DO want
for a moisture profile
Emitter selection, and emitter spacing are key to success.
These factors must be matched to the irrigation run-time, number of starts
and weekly frequency in order to reach our goal of Healthy Plants
with minimum water usage and waste.
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Converting
Your Traditional System to Drip
Converting a traditional irrigation system to drip requires a little
investigative work in your yard.
If you are lucky, you will have a properly
divided set of valves controlling the various zones of your yard, with planting
beds and shrubs on a different valve (zone) than your lawn.
Plants, like trees & drought tolerant that need to be watered less frequently
should not be on the same zone or valve as smaller flowering plants.
Trees and large shrubs especially need to be on separate valves from
lawns that are watered often.
If you are unsure about
this, Click here for more information.
Sometimes the original valving and piping did not take into consideration,
that various plants have considerably differing moisture requirements.
If that is your case, there are still a few things that can be done
without too much difficulty to circumvent this problem. The options for this
are vast, based on what your current situation is. Communications are needed
in order to provide good advice.
Use This Contact Link, or the contact button
on this Website to send a request.
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Converting
Option # 1
DESIGN -
The quickest way to convert would be to connect your new drip components from your
existing rigid-pipe (PVC) system. This has the advantage of being cheaper,
easier, and longer lasting than flexible tubing, but can only be used easily if
your existing system was properly constructed and installed.
Water pressure regulators are required to keep the pressure below 30 lbs.,
this ensures that the drip fittings do not pop apart under pressure.
The next decision is whether you prefer using stand-alone drip emitters or
"dripperline". Click for more information on dripperline.
Stand-Alone drip emitters will work just fine, but they do need to be individually positioned
correctly in order to provide proper distribution of irrigation water.
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DESIGN -
If your existing irrigation system is far from adequate for providing
water supply to the various areas to be drip irrigated, then
draw up a plan to lay out the supply lines to the areas to be irrigated
with a minimum number of 90 degree turns (these increase friction and limit water volume).
A two valve minimum should be considered.
If you intend to design your own irrigation plan, it's critical that you
know how very different runtime and feedrate need to be on various plant materials, and
soil composition types.
It's also critical that you understand how the various drip emitter types
work as well as the aspects of matching feed rate with soil [HCR].
One practical solution to getting a good design is to use the services of
an experienced professional irrigation design technician. Make sure
they understand "Hydro Zoning" and are prone to ask plenty of questions.
To select a technician based on low price can often lead to poor
quality design. Reviews can be misleading. They are worth reading but thay may have been
cherry-picked by the business owner (with some review sites this is possible).
You want A design that provide plant health, water saving and reasonbly easy to install.
You will be spending even more money to install the system, and then live with
for many years.
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INSTALLATION
Initial or Convertion:
-
The actual installation of the Valves, PVC, Supply and Feeder tubing
is not that complex, if you enjoy doing it yourself, and have good design to follow.
Valves & Valve Box
The irrigation design will specify where and how many valve boxes will be installed.
Each valve should have a pressure regulator and filter in-line ahead of it.
Water pressure needs to be limited to 20 to 30 PSI is order to assure connections
along the supply route do not burst. The filter protects the valve from getting debris
stuck it in, which then would cause failure orf the valve. Valves are labor intesive
for installation and replacement. Protecting them is a great idea!
There are plenty of good videos to be found that can help you learn how
to install valves, filters and regulators.
Supply Lines
For homeowner landscapes, these are generally 0.50" ID. PVC (rigid) and Polyethylene (flexible). Outside diameters are
approximately 0.625". The design should specify where the PVC connects to the valves and then where
it connects to the flexible 0.50".
There are many different type of connectors for the many options specified
in the design. To go into all these is beyond the scope of this introductory
irrigation bulletin.
Drip feed Lines
Once the supply lines are within a few feet of the points for irrigation emitters,
the feed reduces to a 0.25" OD & 0.17" ID. These lines then run up to the point where
stand alone Emitters, or Dripperline is connected. Dripperline has the emitters built right into it,
is economical and easy to provide even distribution throughout the root zone area of a shrub or tree.
The best design will minimize any mix of emitter types on any single zone and
will minimize the number of different tubing types. Not all ½"
fittings are compatible with every ½" supply line types. Match all your parts before
you start installing and gluing them together! Burying the supply and feeder lines
improves the attractivness of the system as well as protecting the components from
foot traffic damage.
There are plenty of good videos to be found that can help you learn how
to connect and install your supply and feeder lines.
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Lawns utilize "sprinklers" that spray water. This moisture is not meant to go deep
as the roots for Lawns are usually only a few inches deep.
Many flower or vegetable beds are also sprayed. Often this is done to more
easily spread the moisture out for distribution. In these cases the soil
should have a high [HCR] so that moisture can permeate 6 to 10 inches in
a short period of time. These beds can also be watered by Dripperline without
much complexity. This solves the problem encountered by slow [HCR] soil.
Because Drip Systems are so very valuable for shrubs and trees, it may be worth
reading Bulletin #TB1110 for a clearer understanding.
The most basic aspects of drip systems have been described in this bulletin
in order to help the reader decide if using drip irrigation is right for them
and their landscape. The right system design is needed first, and if the reader is
not familiar with this, the group of bulletins found here
can help.
Not every professional offering drip irrigation design help
is familiar with the critical importance of deep water coupled adequately wide
distribution. You might want to ask them how deep they intend to
have the moisture travel and ask if they do soil settlement tests in order
to match the soil and irrigation.
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