The essential 7.5 elements that every irrigation system should have to reduce costs of
ownership, improve plant health and appearance, and apply water efficiently.
By Kurt K. Thompson
Property ownership is a complicated act of balancing a desired appearance or function with
financial considerations. This balancing act is no more prevalent that in the landscape. It is
made more confusing because of the misinformation or the lack of information available on
which a proper decision can be based.
When asked about the costs associated with the ownership of an irrigation system, most
property owners think only about the costs of repairing broken components of the system. They
never really consider the costs caused by an incomplete design or installation, nor the proactive
maintenance and adjustments to the irrigation system. Both affect the amount of water that is
used, the health of the plants, and the appearance of the landscape.
As an example, most residential property owners would not think that they could be using
between 2,000 to 5,000 gallons in one irrigation cycle. If system is watering 2 times per week,
that means it is applying 4,000 to 10,000 gallons of water. If an average swimming pool holds
18,000 gallons, then the irrigation system applies enough water to fill a swimming pool every
two to three weeks!
What if there it were known that 30% to 50% of that water was not helping the plants? Or
worse, what if this 30% to 50% is not only was wasted, but the poor application of the water
increased the potential for harmful growing conditions for the plants such as disease, pests, and
weeds? In fact, these are both true for most residential irrigation systems. It is the unfamiliarity
with the irrigation piece of the landscape that leads to both of these conditions.
So what contributes to so much non-beneficial and poorly applied irrigation water? The
answers are found in all three of the stages of an irrigation system:
- Design and Installation – Sprinklers in the right place, at the right pressure, with the right nozzles
- Maintenance – Repairing, raising, straightening, realigning, cleaning, etc. AND adjusting to the growing plants and ever-changing conditions in the landscape.
- Management – Creating and adjusting an accurate and specific irrigation schedule for each zone, for each month or season. This includes the time each zone should operate, the number of times per day or week the zones should operate, the time of day the system should operate, etc.
The challenge for a property owner is to distill all of the available information into the very
essential activities that could serve as the foundation for practical landscape irrigation
installation and maintenance. The following are the seven simple elements of a complete
landscape irrigation system that lead to conserving water in the landscape while creating
healthy growing conditions for the plants and soil. There is one small additional element to help
the property owner tie all of the elements together.
The Essential 7.5 Elements
- Sprinklers watering landscape beds and turf are on separate zones (valves).
- Rotating sprinklers and spray sprinklers are on separate zones (valves).
- Operating pressures of the sprinklers are as close to the manufacturer’s recommendations as practical.
- Sprinklers are installed in corners and spaced to overlap each other.
- Irrigation systems do not run when it is raining or has rained.
- Irrigation schedules are changed to match the water needs of the season ormonth.
- Components of the irrigation system are observed operating at least every season to ensure proper operation.
7.5 Utilize licensed and certified professional sprinkler service technicians.
Ignoring these essential seven elements of a complete irrigation system often leads to
unhealthy plants and soils. The increase in landscape maintenance to fight the conditions
created or made worse by poor irrigation practices requires a considerable increase of inputs
such as water, fertilizer, pesticides, herbicides, manpower, equipment, etc. All of the inputs
have a direct and sometimes significant dollar cost. An evaluation and correction to the
irrigation system today can result in savings that can offset the cost of the adjustments and
continue to pay dividends into the future.
1. Sprinklers watering landscape beds and turf are on separate zones (valves).
The frequency and the amount of irrigation required for healthy plants and soils in turf areas
can be very different from what is required for landscape beds (trees, shrubs, and ground
cover). Irrigation that is applied when not needed is the very definition of wasted water.
Therefore it is imperative to control the timing of water application to the turf separately from
the landscape beds.
The timing of water application is defined in two ways: How long to water (runtime) and how
often to water (frequency). Both are guided by the amount of water that exists in the soil
after the water has been removed by the plants and evaporation.
As a general rule, landscape plants (shrubs and trees) use the water at a different rate and
quantity than turf. This is the result of several factors: the natural water use needs of the
plants, the amount of leaf surface, and the cultivation practices. Therefore, the sprinklers
watering the turf will need to have different runtimes than those watering the landscaped
plants.
An additional difference is that landscape plants have larger root zones than turf. An
individual turfgrass plant's roots are measured in inches of width and depth. But landscape
plants have root zones that are measured in feet. It is not uncommon to have the roots of
established shrubs or trees extend 1.5 to 3.0 times the plant's canopy. This equates to the
landscape plants having more and significantly longer "straws" to access more water than a
small turfgrass plant. Having more and longer roots typically means the landscape plants
should get watered less frequently than the turf AND for different lengths of time.
When landscape beds are watered for the same time and frequency as the turf areas, the
landscape beds can get more water than they need and/or the turf gets too little. In the first
case, the result is wasted water. In either case, the resulting excessively wet or dry soils
lead to unhealthy soils and plants which can lead to conditions that can promote weeds and
diseases.
This all points to the first element of the seven to minimize wasted water and promote
healthy plants and soils: Separate the landscape beds from the turf by putting their
respective sprinklers on separate valves (zones). This way they can have different runtime
AND frequencies to meet their different plant water needs.
2. Rotating sprinklers and spray sprinklers are on separate zones (valves).
The two basic types of sprinklers used in landscape irrigation are rotating sprinklers (rotors
or rotators) and spray sprinklers. Visually, the rotors and rotators have streams of water that
move (rotate) and sprays have a fan-like spray that does not move. The principle difference
between the two that can affect wasted water is the rate at which each applies water to the
plants. The scientific term for this is called the precipitation rate.
On average, rotating sprinklers apply water at rates approximately 0.30 to 0.80 inches per
hour. Compare that to the rate for spray sprinklers of approximately 1.2 to over 2.00 inches
per hour. Both are good products, but when using them, it is important to know that sprays
apply water 3 to 5 times FASTER than rotors or rotators.
In terms of controlling wasted water, when sprays and rotating sprinklers are on the same
valve, the areas covered by the sprays will be 3 to 5 times WETTER! (Author's Note: There
is one type of spray that is an exception.) This, too, creates either overly wet or dry areas
and therefore unhealthy plants and soils.
This leads to the second element of the seven to minimize wasted water and promote
healthy plants and soils: Put rotors or rotators on separate valves (zones) from spray
sprinklers. This again allows the sprinkler types to be timed to match the different outputs of
water.
3. Operating pressures of the sprinklers are as close to the manufacturer’s recommendations as practical.
Manufacturers design and make nozzles for sprinklers to operate within a specific range of
pressures (psi). Trained irrigation professionals use the nozzle performance charts from the
manufacturers to give them the minimum and maximum pressures for a specific type of
sprinkler with a specific nozzle.
The difference is when the sprinklers are operating in the middle of the
range (the recommended range) they are closer to optimum performance. When operating
them towards either end of the range, the performance can be just adequate. The closer to
optimum performance, the better the chances are to avoid poor coverage (wet or dry areas).
When dry areas are noticed, the common remedy is to increase the runtimes to get the dry
areas more water. This makes the sufficiently covered areas wet and the wet areas wetter.
Addressing the cause of the pressure problems is the recommended action.
This is the basis for the third element of the seven to minimize wasted water and promote
healthy plants and soils: Design the water source and the piping system, along with
sprinkler and nozzle selection, to ensure the sprinklers are operating as close to optimum
pressures as practical (as defined by the manufacturers). This will help to avoid overly wet
or overly dry areas.
4. Sprinklers are installed in corners and spaced to overlap each other
All sprinkler nozzles are designed by all manufacturers to provide the most uniform
coverage when overlapping each other. This requires that sprinklers be placed in all
corners AND each sprinkler throws water all the way to the sprinklers next to them and
across from them.
This does not have to be perfect as can be seen in the illustration above. Without sprinklers
in the corners, the areas in the corners will not receive the same amount of water as the rest
of the irrigated area. This will result in having to run the sprinklers longer to compensate,
and then the middle areas will get too wet. Then the run times will have to be reduced, and
the corners will be too dry. This constantly fluctuation between overly wet and overly dry
wastes water and makes for stressed plants and poor growing conditions.
So the fourth element of the seven to minimize wasted water and promote healthy plants
and soils: Sprinklers are installed in corners and spaced to overlap each other.
As a side note, all of the sprinklers need to have the correct nozzle installed. They almost
NEVER all have the same nozzle in them, even if they come from the factory that way.
Scientifically speaking, the gallons per minute of the nozzles need to be proportionate to the
degree of arc they cover. The sprinklers also need be adjusted (and kept in adjustment) so
that they do not water walkways, driveways, or other areas not intended to receive water
from the sprinklers.
5. Irrigation systems do not run when it is raining or has rained.
At the very core of being responsible to avoid wasting water in the landscape is to ensure
the irrigation system should only apply water when it is needed by the plants and NOT just
when the controller is scheduled to operate. This means that when Mother Nature supplies
adequate water to the plants in the form of rainfall, the irrigation system should not operate.
The scientific reasons for this can be understood by thinking about the needs of the plants
for air and water in the soil containing their roots. Too much water means not enough air.
So if tiny spaces within the soil have been filled with rainwater, applying irrigation during or
too soon after the rainfall event can make the soils lack the right balance of air and water.
Not enough air in the soil leads to any number of bad situations for the health of the plants.
To prevent the controller from operating as scheduled when there has been adequate
rainfall, all controllers should have a rain shut-off device. The least costly type of rain shutoff
device is a rain switch (also called a rain sensor). It can be attached to the controller
using a hard-wired or wireless connection. It works by setting a series of rain-absorbing
discs to block the controller’s signal to the valves when adequate rainfall has occurred.
A second common type of rain shut-off device is a soil moisture sensor. A high-tech sensor
is placed into the soil and it transmits (hard-wired or wirelessly) the level of moisture in the
soil to a receiver that is wired to the controller. The receiver is set up to block the signal to
the valves just like the rain sensor. A soil moisture sensor is complicated enough that a
professional irrigation contractor should complete the installation and setup.
So the fifth element of the seven to minimize wasted water and promote healthy plants and
soils is: Every controller should have a rain shut-off device in order to prevent the irrigation
system form applying water during or after it rains. This helps keep the right balance of
water and air in the soil.
Unknown to many end users, a rain shut-off device is required by law in many states and
localities. At the very least, it is part of the Irrigation Association’s best management
practices, the EPA Water Sense program, and most all other minimum irrigation standards.
6. Irrigation schedules are changed to match the water needs of the season or month.
If the plant types and sprinkler types are controlled separately by being placed on different
valves (zones), and there is a rain shut-off device installed on the controller, then the timing
of the water application can effectively be regulated by the irrigation controller. This is
typically accomplished by adjusting the amount and frequency of the irrigation based on the
changing needs of the plants within each irrigation zone commonly referred to as the
irrigation schedule.
The changes in water needs of the plants are driven by a number of ever-fluctuating
conditions of the landscape within each zone:
- The size of the plants as they grow
- The time of the year (plant growth cycle – blooming, fruiting, etc.)
- The number of plants (adding or changing plants)
- The changes in the weather
At the basic level, the irrigation schedule should be adjusted seasonally. Unfortunately, it is
typical that a schedule is entered into the controller at the beginning of the year intending to
satisfy the highest water needs of the year. Then the schedule is never changed during the
year. This causes too much water to be applied in the spring and fall (and winter if there is a
12 month irrigation year).
As the plants move through their annual growth cycle and the weather
changes, so does the water need – more during the summer months and less in the spring
and fall. Any water above that line does not benefit the plant and has the potential to
contribute to the conditions for poor plant health caused by overly wet soils.
The dark-shaded area represents the amount of water wasted by setting the controller to
satisfy the peak water needs of the plants at the beginning of the year and not adjusting it
until the system is turned off for the winter. This demonstrates the common claim that when
the first four rules of preventing wasted water are combined with adjusting the controller
monthly, it typically reduces the irrigation water use by 20% to 50%.
Each lightly shaded area represents a monthly adjustment made to more closely meet the
needs of the plants. While it would increase the amount of wasted water compared to
monthly adjustments, these can be simplified into four seasonal adjustments: On (or
adjusted) for the spring; Adjusted for the summer; Adjusted for the fall; Off (or adjusted) for
the winter.
Therefore, the fifth element of the seven to minimize wasted water and promote healthy
plants and soils is: Adjust the irrigation schedule to meet the changing plant water needs at
least seasonally, or better yet, monthly.
This can be accomplished automatically by features found in some more advanced (but still
very affordable) controllers or the even more advanced “Smart” controllers. For Smart
controllers to be effective, the first three rules MUST be in place and a trained professional
is needed to set up the controller with specific information about the sprinklers, the plants,
the soils, and other conditions in the landscape, and only trained professionals are allowed
to make adjustments.
7. Components of the irrigation system are observed operating at least two times per irrigation year to ensure proper operation.
Most landscape irrigation systems are scheduled to operate during times of the day when
they will not interfere with the use of the landscape. This typically means they operate in the
wee hours of the morning. The result: No one sees them and therefore does not know if
they are operating correctly. The effect of things that might be out of adjustment or broken
can often be invisible until the physical damage they cause becomes extreme or plants are
dead. The sooner the problem is identified, the more the negative effects can be minimized.
The simplest of things can create significant amounts of wasted water or unhealthy
conditions for the plants. Examples of sprinkler problems that regularly require adjustment
regardless of the quality of installation are:
- Crooked or Tilted
- Misaligned – Water is not going where it is intended
- Sunken – Sprinkler does not pop up high enough
- Broken – Mower, vehicle, or vandalism damage
- Clogged – Debris in the system clogs the sprinkler filter or nozzle
- Overspray - Sprinkler throws onto the fence, building, roads, driveways, or sidewalks
- Blocked – Plants normal growth obstructs the water from getting to the intended areas
- Leaks – Aging seals in sprinklers, sprinkler connections to pipes, or the pipes themselves
- Changes in Pressure – As the development or community is built out, the demand for water increases and everyone is irrigating during the same hours causing the pressure to decrease
Thus the seventh element of the seven to minimize wasted water and promote healthy
plants and soils is: At least two times during the irrigation year, all sprinklers, valves, rain or
soil moisture sensors, and other critical components should be observed in operations and
maintained. This may not be frequent enough for components like filters, lake screens, foot
valves, or others.
An irrigation system is much like the braking and suspension systems in an automobile:
they both are essential support systems which require regular preventative maintenance.
Preventative maintenance beyond just regular observations may prevent catastrophic
failures and lower the operational costs of the irrigation system. The items that are
preplaced BEFORE they fail as part of a yearly preventative maintenance program should
include items such as: valve solenoids or diaphragms, rain sensor discs, waterproof wire
connectors at the valves, riser seals in sprinklers, and worn sprinkler nozzles. The
frequency of these preventative maintenance actions ranges from between 3 and 5 years,
depending on how often the system is used during the year.
7.5 Look for Licensed and Certified Professional Irrigation Contractors
The average person owner does not perform anything more than the most simple of
maintenance activities on their automobile because of complexity, time, or a lack of
understanding of how working on one component will affect the operation of other. An
irrigation system is no different. But finding a professional who does understand these
things about an irrigation system can be intimidating. This is where national trade
associations can help. Look for landscape and irrigation professionals with irrigation
licenses (where required) and/or national certifications.
The Irrigation Association (IA) is the national certifying body for
the irrigation industry that offers the following certifications that
would benefit both residential and commercial property
owners.
- Certified Irrigation Contractor: Experienced business owners who execute irrigation projects to install, maintain and repair irrigation systems.
- Certified Irrigation Designer – Residential, Commercial, or Golf: Establish specifications and design drawings for irrigation projects.
- Certified Landscape Irrigation Auditor – Landscape or Golf: Evaluate the irrigation system conditions and water-use data, as well as test and measure the components.
- Certified Landscape Water Manager: Evaluate, operate, manage and improve landscape irrigation systems to achieve the highest level of water conservation possible.
- Certified Irrigation Technician: Technicians that install, maintain, and repair irrigation systems.
The professionals who have achieved these credentials must complete continuing education
to maintain them. Look for companies that are active in the state or local trade associations
and community events. They have the industry and local knowledge that provide the best
possible solutions to minimize wasted water and promote healthy plants and soils and focus
on industry best practices to ensure high value for the money invested.