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Five Steps to Successfully irrigating with harvested Water

Prepared by Lynette Von Minden

2 Five Tips to Successfully Irrigating with Harvested Water

Over the years, water shortages and restrictions have become the norm for people living in drought-prone regions throughout the world. However, any region—desert or otherwise—can experience unusually dry conditions at any time. The severe drought in the Southeastern United States during 2007 demonstrated that even an area which historically averages over 50 inches of precipitation annually can suffer from an unexpected water shortage. Rapid population growth in “Sun Belt” regions of the U.S. is also having a tremendous impact on limited fresh water supplies. In 2005, the Census Bureau projected that approximately 88 percent of the U.S. population growth between 2000 and 2030 will occur in the Sun Belt. More and more people are making their homes in cities like Las Vegas, for example—a city which grew from a population of 164,674 in 1980 to 478,434 in 2000, yet averages a mere four inches of rain each year. This tremendous population growth places an enormous strain on already limited lake and groundwater resources. Regardless of its cause, the scarcity of potable water has become front page news worldwide, and the need to advocate and practice intelligent water use is imperative.

the case for water harvesting

Due to the world’s widespread water woes, water experts everywhere are advocating the process of water harvesting—capturing, diverting and storing non-potable, or “reclaimed,” water for landscape irrigation and a

variety of other uses. For years, some conscientious individuals have embraced smart water use by integrating small-scale water harvesting systems like rain barrels into their landscapes. Now, because of technological advances and the growing need to conserve potable water, specifiers and landscape architects are finding that water harvesting is an increasingly popular choice for larger applications like commercial sites, schools, apartment complexes and parks.

Why? In addition to the obvious benefit of saving potable water for drinking and bathing, there are many other compelling reasons to harvest and reuse water:

Harvesting rainwater and stormwater (rainwater that accumulates on paved surfaces as runoff) can reduce the possibility of damage from flooding and erosion at building sites, offering dual benefits to property owners and developers. Furthermore, properties can use their water harvesting systems as a public relations tool to create a positive, environmentally-responsible image that attracts tenants and patrons.

What is “Water Harvesting?” The collection and treatment of rainwater, stormwater, greywater, HVAC or steam condensate water from commercial or residential facilities for subsequent reuse as toilet flushing water, boiler or cooling tower make-up water and/or landscape irrigation water.

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Because it’s likely that water authorities will begin charging higher prices for potable water in the future, water harvesting could also potentially keep water bills at a manageable level.

Harvesting water for landscape irrigation can be as simple as capturing rainwater in a bucket and using it to fill a watering can. When harvesting water at larger public or commercial sites, however, the process has the potential to become much more sophisticated. As anyone who works in the construction or irrigation industry already knows, the LEED® (Leadership in Energy and Environmental Design) program has spawned greater interest in water harvesting. Sites can receive anywhere from six to ten LEED certification points by simply harvesting water and integrating water-efficient irrigation systems. (For more information, see Rain Bird’s Quick Guide to LEED, Rain Bird’s Water-Efficient Products Guide and Rain Bird’s Non-Potable Products List at www.rainbird.com/landscape/resources/LEED/Library.htm.) Because of this fact, implementing a water harvesting system is an excellent way for specifiers to help their clients’ projects obtain LEED certification. LEED-certified properties save significant amounts of water and energy, simply having this certification helps properties appeal to the growing number of individuals and organizations concerned with environmental stewardship.

While pursuing LEED certification is voluntary, some state and local agencies are mandating that new commercial properties and government facilities harvest water. The city of Tucson, Arizona, for example, now requires that all new commercial building sites harvest at least 50 percent of the water that they use for landscape irrigation. This water can be collected in various ways,

and designers must submit site water budgets and water harvesting plans to demonstrate compliance with city regulations. While Tucson’s desert location certainly explains the city’s need to promote water harvesting, many other cities are likely to follow its lead—even cities in cooler, wetter climates. In addition to the Southwest, many other regions are offering tax incentives and rebates to both residential and commercial buildings that harvest water. When you combine these incentives with the rising cost of municipal water and sewer services, it’s likely that harvesting water for landscape irrigation will become increasingly commonplace—and in some areas, absolutely necessary—in the very near future.

What does all this mean for specifiers and landscape architects? It’s possible that many, if not the majority, of new commercial buildings will soon require some form of water harvesting system to be constructed and linked to their landscape irrigation systems. As a result, it’s likely that those professionals who haven’t yet designed and implemented water harvesting systems for landscape irrigation soon will. Specifiers and architects will not only need to understand water harvesting, but they’ll also need to learn how this process affects the ultimate design of a site’s irrigation system. Because non-potable water often has different chemical properties than fresh water, its effects on the site’s turf, trees, plants and irrigation system components will also need to be considered. Professionals who can successfully balance these considerations will be better poised to provide well-rounded solutions that lead to satisfied clients. This in turn, will help them develop enviable project portfolios that can lead to additional business and increased revenue.


Water harvesting basics

There are two primary types of water harvesting methods—passive and active. In passive water harvesting, no mechanical systems are used to gather water. Rainwater and stormwater that cannot be immediately absorbed by the landscape is simply collected and contained through a number of other means, including vegetative swales, wetland ponds, dry creek beds, green roofs and pervious concrete or concrete pavers. These passive collection methods are relatively simple and inexpensive, only requiring that builders, specifiers and landscape architects stay mindful of “green” practices and intelligent water use during a project’s planning and construction phases.

Active water harvesting involves using mechanical systems to collect, filter, store and recycle rainwater, stormwater, cooling system condensate and “greywater”—water that has already been gently used for the purposes of hand-washing, showering, bathing, dishwashing or laundry. These four types of non-potable water are proactively collected through the use of containment systems located above or below ground level. Active water harvesting systems include the tanks, piping, metering, pumps and other infrastructure elements needed to store, treat and transmit this collected water for beneficial use. These systems may be gravity-flow-based or pump-based depending on the size and needs of the site.

If it’s not used for landscape irrigation or toilet flushing, for example, greywater is sent through municipal sewer systems, effectively being thrown away while it could still serve a major purpose. A primary advantage of active water harvesting is the fact that the occupants of almost any building generate a steady, predictable supply of greywater. Because supply can be predicted, it can be matched to demand, requiring less money to be spent on water storage. Greywater can contain detergents, fibers and skin cells, however, so it must be properly filtered to keep it from developing odd colors and odors during storage. Many municipalities have established codes that require reclaimed water to meet certain levels of purity before it is stored for this very reason.

Both active and passive water harvesting methods are excellent ways to use water wisely, minimizing or even eliminating the use of municipal water for landscape irrigation. While collecting water

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anatomy of an active Water harvesting System


through passive means is relatively simple, it does offer less control over how much water is collected, stored and applied to the landscape. On the other hand, depending on a site’s climate and physical characteristics, an active harvesting system can often provide a complete supply of water for landscape irrigation, supplementing it with municipal water if necessary. Actively harvesting water requires more forethought, planning and monitoring than passive collection, along with a larger initial investment in systems and materials, but it can also provide a greater return.

the Process Of active Water harvesting

1) Water Collection: Rainwater is typically collected from building rooftops, while stormwater is collected from parking lots and other impermeable surfaces. In some active systems, greywater is collected from showers, sinks and washers. Water from toilets and kitchen sinks is not collected due to an extremely high level of contaminants.

2) Pre-Filtering: Rooftop rainwater is relatively free of contaminants, but it must be

screened for leaves, gravel or other debris. Screens and filters can be used to separate out larger debris particles. Pre-filtering stormwater and greywater is sometimes done with settling tanks that allow heavy debris to sink to the bottom and lighter debris to float to the top. A strainer floating below the surface pumps the cleaner water to the harvesting system.

3) Storage: Storage options for harvested water depend on the amount of supply and demand, the frequency of rainfall in the area and the availability of space to house or bury the tanks. Tanks can be fabricated from polyethylene, fiberglass, concrete or steel and tank sizes can range from a few hundred gallons to a half a million gallons or more.

4) Sterilization: Water in storage must be treated with a sterilizing agent to keep the water clean. This can be done by chemical addition of chlorine, chlorine dioxide, ozone, by recirculation past ultraviolet (U.V.) sterilizers or a combination of processes.

5) Final Filtration: A secondary filter removes remaining particulates in the water

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ControlsManages & monitors all aspects of the process

the Process of active Water harvesting


before it is stored, improving the water’s purity and clarity. This can be achieved with a sand filter or bag filter for most uses. Reverse osmosis and carbon filters are also used for greywater filtration, often taking the water to near-potable quality.

6) Controls: Water harvesting systems in commercial and institutional buildings are held to a higher standard than in residential buildings. These systems generally require a sophisticated computerized control system that manages and monitors all aspects of the process, from collection and filtration to eventual reuse.

Five Steps to Successfully irrigating with harvested Water

For many reasons, harvesting water for landscape irrigation just makes good sense. However, every site has different physical characteristics, irrigation needs, collection opportunities and state or local regulations to consider. Before jumping into the design, construction and implementation of an irrigation system fed by water harvested on site, it’s important for specifiers and landscape architects to gain a firm understanding of a project’s needs, current situation, budget and desired end result. Following these five steps can ensure the development of solid plans that support The Intelligent Use of Water™ and result in the best possible outcomes.

Step 1: . . . . . . . . . . . . . . . . . . . . . .help your clients decide whether water harvesting is the right choice for their sites. There are many reasons that can cause clients to express interest in water harvesting. Knowing and recognizing the primary motivation is necessary for an end result that meets client expectations.

For example, a developer who wants to earn LEED certification for a new office complex will need to abide by certain design and implementation standards that the manager of a shopping center who wants to reduce utility bills will not. Because water harvesting is just beginning to become more commonplace, many clients may not even realize that water harvesting is a possibility for their sites. In these situations, it’s up to the architects, builders and specifiers to become knowledgeable about the processes involved and suggest this environmentally-friendly option when appropriate.

Here are a few of the most common reasons that the developers or owners of commercial sites may choose to install water harvesting systems:

They have a genuine interest in reducing •the impact that their commercial or public site has on its environment.

They are seeking LEED accreditation •for their building.

The local municipality has asked them to •reduce the amount of rainwater entering the sewer or stormwater system at their site.

They want to save money on potable water •costs by investing in a water harvesting system.

They are cultivating a positive environmental •public image for their organization.

A local ordinance restricts the amount of potable •water that they can use for landscape irrigation.

Obviously, there may be a combination of reasons behind the decision to harvest water at a particular site. Understanding all of the reasons involved can help specifiers and architects work more successfully with water harvesting and irrigation specialists to develop a system that satisfies their clients’ needs—both now and well into the future.


Step 2: . . . . . . . . . . . . . . . . . . . . . .estimate how much water will be needed for landscape irrigation.At sites with existing irrigation systems and landscapes, it’s possible to analyze past water bills for a fairly accurate estimate of landscape irrigation water use, taking seasonal fluctuations and system efficiency into account. For new landscapes and structures still in the planning or construction phases, this estimate will depend greatly upon the types of plants, shrubs, trees and turf chosen for the site. Obviously, if limiting or eliminating the need to supplement harvested irrigation water with municipal water is imperative, the landscape may include more plants and less turf, for example. For an accurate estimate of the amount of water a client will need for landscape irrigation, determine answers to the following questions:

For new sites, what will the landscaped •area be in square feet?

What types of plantings (turf, shrubs, •flowers) are present or planned for the site and where are they located?

What’s the prevalent soil type at •the site—clay, loam or sand?

What types of technology will most •efficiently irrigate the site—overhead sprays and rotors, drip or subsurface?

How many irrigation stations •(zones) will there be?

How many GPM (gallons per minute) •will the irrigation system require and at what pressure level?

How many gallons of water will the •system require per month?

Will the irrigation system be supplemented •with municipal water if the harvested water supply is inadequate or runs dry?

Step 3: . . . . . . . . . . . . . . . . . . . . . .establish renewable water resources at the site.It’s tempting to try to collect every possible drop of rainwater or greywater, but it’s important to evaluate each site’s unique situation before moving forward. For example, it may be very environmentally responsible to recycle the water from sinks and showers, but it can be very difficult and expensive to retrofit plumbing systems to harvest this greywater in an existing structure. If a building is still in the design or construction stage, it’s far easier to implement the appropriate pipes and fixtures for this purpose. In other words, be realistic about how much water a site can reclaim for irrigation purposes by answering the following questions:

What is the average rainfall experienced •at the building’s location?

What is the current or planned design •and square footage of the building’s roof? What percentage of it could receive collectible rainwater?

Does the site’s cooling system •generate condensate that could be harvested? If so, how much?

Is there or will there be a sump pump that •can generate groundwater for reuse?

If the plan is to harvest greywater from inside •the facility, how much are its occupants expected to generate through the use of sinks, showers, washers or other sources?

Step 4: . . . . . . . . . . . . . . . . . . . . . .Designing the water harvesting systemAfter determining how much water is needed for irrigation and the prospective sources of that water, it’s time to work with a water harvesting specialist to design the system. Design


considerations include storage type and location, equipment location, local regulatory issues and system controls and reporting capabilities.

Storage:Many factors play into the decision of whether to store water above ground or underground. Storing water above ground is one way to let others know that a building is harvesting water, which can project a positive public image. However, not every building’s architectural style is complemented by visible cisterns or tanks. Water stored above ground is also susceptible to freezing in cold climates, and it can be difficult to reserve enough physical space on the property for large steel or polyethylene tanks. Conversely, while storing water underground does offer protection against freezing, property owners must bear the costs of excavation to make way for the tanks or vaults. Water stored below ground is also subject to a greater risk of infiltration, and in some regions, high water tables may make it difficult or impossible to have large, subsurface tanks.

equipment Location:Finding an appropriate location to house any pumps needed to move the water from its storage tanks to the irrigation system—as well as sterilize, dye or chlorinate it, if local regulations require—is another design consideration. Some buildings have a mechanical room specifically for this purpose. If the building lacks indoor storage, this equipment can be placed inside a weatherproof housing located outside the main structure. In either case, the types and sizes of the necessary mechanical equipment will depend on the amount of water needing to be moved, local regulatory issues and the desired water pressure. Consider these questions:

Is there a mechanical room where water •harvesting equipment (e.g. a pump) can be located, or will the equipment need to be located outdoors in a separate structure?

Where is your proposed equipment area (or •where will it be when the structure is complete?)

What are the dimensions of the equipment area?•

Is there access near this area to municipal •water for supplemental irrigation use, should it become necessary?

Controls:Sophisticated water harvesting systems often include a computerized, touch-screen controller that monitors the status of mechanical components, water levels in each storage tank and the total amount of water harvested by the system on a periodic basis (often monthly). In many cases, an optional interface can enable Web-based control for convenient access from any computer with an Internet connection.

When water is being harvested for irrigation, it’s also possible to integrate smart, or weather-based, irrigation control like for a complete package. In fact, many cities require that sites harvesting water for irrigation install smart irrigation controllers like Rain Bird’s ET Manager™ or its ESP-LX Controller or ESP-LXD Two-Wire Decoder Controller, both with optional ET Manager Cartridges. These smart controllers enable harvested water to be used as efficiently as possible, taking details such as evapotranspiration, effective rainfall, temperature and humidity into account.

Larger sites can benefit from the addition of central control software that makes it possible to manage irrigation from a desktop or laptop computer.


For a client who needs to manage multiple irrigation sites, central control software like Rain Bird’s Maxicom2® or IQ™ Central Control Software offers both convenience and flexibility. Clients with one large, contiguous irrigation site to manage can benefit from Rain Bird’s IQ or Site Control software. These types of programs not only offer the ability to schedule irrigation from a remote location, but they can also provide advanced features such as advanced reporting, flow monitoring, lighting system control and automated ET management.

Consider these questions when determining the appropriate level of control for any water harvesting system:

Who is in charge of irrigation management •and maintenance, and where are these individuals located—on-site or off-site?

How many sites must be managed, •and how large are they?

Does the local municipality require the •amount of non-potable water being reused for irrigation to be reported?

If reports are required, how often •must they be generated and what type of data must they include?

Do any of the users need the ability to •access the system remotely via the Web?

Will smart irrigation controls be incorporated •into the water harvesting system or will irrigation control be kept separate?

Would the site and its grounds maintenance •professionals benefit from the addition of central control software?

Step 5: . . . . . . . . . . . . . . . . . . . . . .evaluating or designing the irrigation system Now it’s time to take another look at the landscape’s irrigation needs. Step 2 examined the amount of water needed for irrigation, the types of plants and turf present or planned in the landscape, required irrigation system operating pressure, number of zones, soil type and the type of irrigation needed (overhead sprays and/or drip, for example). Regardless of whether an irrigation system at a site is new or existing, if it’s going to be supplied with harvested water, it must adhere to local regulations for non-potable water use.

Non-potable water supplied to irrigation systems must be kept completely separate from a site’s drinking water source. Many municipalities also require that irrigation systems be designed to prevent “ponding” of non-potable water and there is no overspray onto picnic areas, sidewalks or neighboring properties. If a harvested water supply will be supplemented with a municipal water source for irrigation, a backflow prevention valve must be installed on the potable water service into the building. This prevents cross-contamination between harvested water and the water used for drinking and showering. Some municipalities require that a licensed plumber install the backflow prevention valve; others allow irrigation contractors to perform the installation.

Spray heads, valves and pipes intended for use with reclaimed water are identifiable by their purple color. Local ordinances will dictate any need to retrofit existing systems with these purple components. In some cases, rather than replacing components with those specifically intended for non-potable water, existing system components must only be marked with tags


identifying them as such. For example, the city of Tucson, Arizona does not require existing irrigation pipe to be replaced with purple pipe unless the irrigation system is being expanded, repaired or otherwise significantly modified. However, all new systems designed for use with reclaimed water must use specialized purple pipe, purple controller boxes and purple spray heads.

If a business or organization takes the time and effort to install a water harvesting system, it only makes sense that its irrigation system should be as efficient as possible. Today’s irrigation technology uses less water than ever before, making now the perfect time to audit and retrofit an existing system or install a highly-efficient new system. In addition to smart controllers and central controls like those mentioned in Step 4, soil moisture sensors and rain sensors, like Rain Bird’s SMRT-Y Soil Moisture Sensor Kit and WR2 Rain/Freeze Sensor can make any system more efficient. The SMRT-Y measures the actual moisture present in the soil and relays that reading back to the controller for what’s called “closed-loop irrigation.” With user-controlled thresholds for rainfall and temperature, the WR2 prevents unnecessary watering.

It’s also important to specify rotors and sprays that use matched precipitation rates and pressure regulation for optimum coverage and water-efficiency. Rain Bird’s 5000, 5500 and 8005 Series Rotors all offer Rain Curtain™ technology for larger water droplets and superior close-in watering with optional pressure regulation. Swing joints with integrated pressure regulation can also maintain a constant pressure at the rotor for more efficient operation. Nozzles with check valves can reduce water seepage from rotor or spray heads located at or near the bottom of a hill

or slope. Rotary nozzles are an excellent choice for sloped areas or clay soil, as they apply water at a lower precipitation rate that allows it to be absorbed rather than run off. When appropriate, drip irrigation and subsurface irrigation can be up to 70 percent more efficient than overhead sprays.

The right combination of water-efficient irrigation system components can ensure that very little harvested water is wasted during the irrigation process. For more specific irrigation product information, see Rain Bird’s Water-Efficient Products Guide and Rain Bird’s Non-Potable Products List.

the future of water harvesting

Water harvesting is not simply a trend that will quickly come and go. It’s likely that future water shortages both in the United States and internationally will continue, making it necessary for all of us to reduce the amount of potable water we use for irrigation. Harvesting rainwater, stormwater, cooling system condensate and greywater is a smart and relatively painless process that can conserve significant amounts of fresh water for drinking. Using these unconventional sources of water responsibly while also incorporating today’s water-efficient irrigation technology is the best way to continue maintaining beautiful, healthy landscapes with little impact on the world’s fresh water supply.

As a provider of irrigation systems and components, Rain Bird supports The Intelligent Use of Water™ through the ongoing development of efficient irrigation technology. By working together to create water-efficient systems that make the most out of every drop of water—both potable and non-potable—we can ensure that our fresh water supply exists for the benefit of future generations.

Based in Azusa, Calif., Rain Bird Corporation is the world’s leading manufacturer and provider of irrigation products and services. Since its beginnings in 1933, Rain Bird has offered the industry’s broadest range of irrigation products for farms, golf courses, sports arenas, commercial developments and homes in more than 130 countries around the globe. To learn more about Rain Bird and its industry-leading irrigation solutions, visit www.rainbird.com or call 1-800-raiN BirD.

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responsibility to develop products and

technologies that use water efficiently.

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our industry and our communities.

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