The population of our nation currently withdraws from the available water supply about 408 billion gallons of water each day. 57 percent of that water is used for domestic purposes including drinking water, sanitation, cooking, and landscape irrigation. About 33 percent of all water withdrawals in the United States are related to some form of agricultural irrigation. According to the United States Department of Agriculture, about 80% of the nation’s consumptive water use is for agricultural purposes. Consumptive water use is defined as water which is removed from available water supplies and then is not returned to any type of water source. Those sources could include rivers, lakes, streams, or even a water or sewage treatment facility. Worldwide about 70% of all freshwater withdrawals are for agricultural uses. The world water usage has tripled over the past fifty years as the population has increased. In developing areas the lack of safe drinking water and sanitation remain huge issues. It is estimated that a child dies every seventeen seconds as a result of water borne illnesses. It is easy to look at the volume of water usage for irrigation purposes and realize that it is vital that we look at alternatives to the use of potable water whenever and however possible. 

More and more irrigation systems around the United States are using reclaimed or recycled water. It is important to consider a number of factors before we move forward using reclaimed or wastewater on any type of irrigation system. There are two major classifications of irrigation systems which include either a landscape or an agricultural system. As we look at these irrigation systems and the possibility of water reuse, let’s review a few terms and definitions that are important in this discussion.

What is water reuse? Water reuse can be defined as the use of reclaimed water for any beneficial purpose as a substitute for the use of potable water. The use of reclaimed water for irrigation and other purposes has been employed as a water conservation practice in a number of states for many years.

What is reclaimed (recycled) water? Reclaimed water, also known as recycled water, is water recovered from domestic, municipal, and industrial wastewater treatment plants that has been treated to standards that allow safe reuse. Properly reclaimed water is typically safe for most uses except human consumption.

What is waste water? Waste water is not reclaimed water. Waste water is untreated liquid industrial waste and/or domestic sewage from residential dwellings, commercial buildings, and industrial facilities. Gray water, or untreated wastewater from bathing or washing, is one form of waste water. Waste water may be land applied, but this is considered to be land treatment rather than water reuse. Waste water is not sewage. It does not contain any fecal matter, urine, or other similar products. The Uniform Plumbing Code^® defines gray water as untreated waste water that has not come into contact with toilet waste, kitchen sink waste, dishwasher waste, or similarly contaminated sources. Gray water includes water from bathtubs, showers, lavatories, clothes washers, and laundry sinks.

The 2012 Uniform Plumbing Code (UPC) in Chapter 16 Alternate Water Sources for Non Potable Applications provides requirements for reclaimed and gray water systems. Section 1602.2.1 speaks to the discharge of gray water. Gray water may be used for subsurface irrigation purposes only and also shall not be used to irrigate root or food crops intended for human consumption which may come in contact with the soil being irrigated. When using gray water for irrigation it is important that the system be installed and sized to prevent any type of surfacing, ponding, or runoff of the gray water. A surge tank may be required to prevent these problems from occurring. There can be significant health hazards related to using the water in this way. Waste water can contain a mixture of chemical and biological pollutants systems that will not adversely affect the plant life and may be suitable for use with landscape irrigation. (Figure 1)

When we look at agriculture irrigation we are talking about the use of water in the production of crops, livestock, or poultry. It is obvious that when used for these purposes the quality of the water is a critical factor. Around 90% of waste water produced globally remains untreated, however in the United States the percentage of untreated waste water is much less. With that being said, even within the United States and other industrialized nations, the problems do still exist. There can be significant health hazards related to using the waste water in this way. Wastewater can contain a mixture of chemical and biological pollutants which can contaminate crops and poison livestock. As with so many things, waste water and gray water when used correctly will replace the use of potable water in some irrigation situations. Doing so reduces the burden on the potable water supply and at the same time reduces energy and other treatment expenses. It is vital however that the use of waste and gray water must not include any type of agricultural irrigation. The UPC in section 1602.3 Connections to Potable and Reclaimed (Recycled) Water Systems clearly states: Gray water systems shall have no direct connection to a potable water supply, on-site treated nonpotable supply or reclaimed water system. Potable, on-site treated nonpotable, or reclaimed water is permitted to be used as makeup water for a non pressurized storage tank provided the connection is protected by an air-gap in accordance with the code. The simple fact that any connection to the potable supply requires an air-gap drives home the hazard that may exist within the liquid in these systems.

Other water reuse systems can provide us with more suitable options for surface and agricultural applications. We can again look to the UPC for guidance regarding these systems. When we consider reclaimed or recycled water it is clear that the quality of this liquid is normally far greater than that of gray or waste water. Reclaimed or recycled water can be used as a substitute for potable water in a number of ways including to supply water closets and urinals, trap primers, industrial or commercial cooling equipment, and of course both subsurface and above ground irrigation. This liquid has been treated to a level at which it will not pose any health hazard if it comes in contact with the general public. The level of treatment required is normally set by the Authority Having Jurisdiction. In the absence of water quality requirements, the Federal Environmental Protection Agency in EPA/625/R-04/108 also sets quidelines and minimum standards for water use with three exceptions.

• Water treatment is not required for rainwater catchment systems used for above ground irrigation with a maximum storage capacity of 360 gallons
• Water treatment is not required for gray water used for subsurface irrigation
• Water treatment is not required for rainwater catchment systems used for subsurface or drip irrigation

Many jurisdictions have chosen to set their own standards. As an example, figure two represents the recycled water quality standards set forth by the Colorado Department of Public Health and Environment in their regulation 84. This table was put together by the Denver Water Company and contains their 2011 reporting data and the limits established by the state in regulation 84. (See Figure 2 below)

Figure 3 lists suggested usages and treatment for recycled water, this table was put together by the United States Environmental Protection Agency as a guide to local and state water suppliers and environmental agencies.

Additional water sources that may be used in irrigation can come from on site nonpotable water systems that may take water from ponds, streams and other bodies of water. The quality of this water is addressed in the UPC in Section 1604.10.2 which states: On-site treated nonpotable water supplied to toilets or urinals or for other uses in which it may be sprayed or exposed shall be disinfected. Acceptable disinfection methods shall include chlorination, ultraviolet sterilization, ozone, or other methods as approved by the Authority Having Jurisdiction. This water may be used for landscape irrigation, but should not be used for agricultural irrigation.

Another possibility for a supply of water for irrigation besides the potable water system comes from the heavens. Nonpotable rainwater catchment systems can provide us with an alternate source for both agricultural and landscape irrigation. When we are collecting rainwater for irrigation purposes it is important that the surfaces used to collect this rainwater are correct. Prohibited surfaces for the collection of this rainwater include vehicular parking surfaces, surface water runoff, and bodies of standing water. No treatment of rainwater used for subsurface or non sprinklered surface irrigation is required where the maximum storage is less than 360 gallons according to section 1702.9.4 of the UPC. Storage of rainwater above 360 gallons must be treated to meet the quality requirements of the Authority Having Jurisdiction.

All of these systems will allow us to preserve the small amount of potable water we possess while saving energy on filtration and treatment costs. The problem with a number of these supplies is that they can be greatly affected by outside issues which may lead to a shortage of available supply.  Drought, high usage, and other issues may require these supplies to be supplemented by the public water supply at times. Cross-connection control is an important factor when the potable supply is used to supplement the supply of reclaimed, recycled, gray, or nonpotable rainwater catchment systems. Each of these make up connection is a high hazard or a health risk to the potable supply. The UPC in section 1602.3 requires an air-gap as protection on any make up line feed a gray water system. The potable water supply to any non potable rainwater and reclaimed water systems shall be protected by either an air-gap or by the installation of a reduced pressure principle backflow preventer as stated in section 1603.4 and section 1702.4. The use of an unprotected spool connection (Figure 4) or a swing connection (Figure 5) are strictly prohibited. Both of these connections would require the installation of a reduced pressure principle assembly on the potable supply, immediately upstream of these connections.

The UPC also mandates specific testing is performed to ensure that no cross connections exist is recycled, reclaimed, or non potable rainwater catchment systems. These systems are in many cases under constant pressure and as a result may present a greater hazard for contamination of the potable water supply that we would encounter with a gray water system.

Recycled or reclaimed water systems may include hose bibbs, these hose bibbs are required to be marked and labeled as nonpotable water. The connectors used must differ from those used in the potable supply system.  All piping, valves and equipment shall be labeled and identified as nonpotable water. The entire system shall undergo an initial cross-connection test  as stated in UPC section 1603.5. Annual testing is also required in accordance with UPC section 1603.11.2 Annual Cross-Connection Inspection and Testing: An initial and subsequent annual inspection and test shall be performed on both the potable and reclaimed or recycled water systems. The potable and reclaimed or recycled shall be isolated from each other and independently inspected and tested to ensure there is no cross-connection in accordance with section 1603.11.2.1 through sections 1603.11.2.4.  Section 1603.11.2.1 Visual System Inspection also states: Prior to commencing the cross connection testing, a dual system inspection shall be conducted by the Authority Having Jurisdiction and other authorities having jurisdiction as follows:

1. Meter locations of reclaimed or recycled water and potable water lines shall be checked to verify that no modifications were made and that no cross-connections are visible
2. Pumps and equipment, equipment room signs, and exposed piping in equipment rooms shall be checked
3. Valves shall be checked to ensure that valve lock seals are still in place and intact. Valve control door signs shall be checked to verify that no signs valve been removed.

UPC section 1603.11.2.2. Cross-Connection Test describes in detail the test procedure itself which includes a number of subsections to test flow, pressure, fixtures, and outlets, valves, and each and every system component.

The testing is very similar for nonpotable rainwater catchment system and is detailed is UPC section 1702.11 through section 1702.11.2.4.

Since the surface of the planet Earth is covered with almost 70 percent water you would think that we would possess an almost limitless supply of this life giving liquid and that we could use it in any way we see fit. Sadly that is not the truth. Less than three percent of the total amount of water on our planet is potable water. The world population is growing at an incredible rate. Each day we add over 200,000 people to our planet. To look at it another way the world’s population in 1960 was about three billion people. In 1999 it was about six billion people and in 2025 it is estimated to be about eight billion people. We need to figure out how to do more with less, and how to reuse, reclaim, and recycle water whenever and wherever possible. We need to do this while at the same time protecting the small amount of clean potable water available to the world population.

We are making piping systems more complicated while at the same time we continue to make the installation of these systems require less skill than had been needed in the past. The use of plastics, press fit fittings, push on fittings, and other joining methods have made the interconnection of piping systems easier. Labeling of piping, valves and fixtures is now far more important than it may have been when most facilities used only the public water supply within their buildings. The UPC in Section 601.2 Identification of a Potable and Nonpotable Water System, clearly lays out the requirements for the labeling of pipe and other components within these systems. (See Figure 6)

It is important that everyone involved in the design, installation, inspection, and maintenance of these systems understands both the benefits of these systems and the potential hazards that may result from their use. Water reuse when performed properly is an environmentally sound practice that saves energy, preserves our supply of fresh potable water and is becoming more and more popular within the United States and on an international level. The population growth we are currently experiencing on our planet is going to put increased pressure on the water supply worldwide. Irrigation needs for agricultural purposes will only continue to expand as our population grows. We need to have the systems in place to provide both the trained people and the materials ready to expand the use of all types of non potable water in irrigation, manufacturing, sanitation, and other areas as needed. The future is now.

About the Author

Sean is a 40 year member of the United Association Local 524 Scranton Pa. He has worked in all phases of the plumbing and mechanical industry and is a licensed master plumber. Sean is a Past President of the American Society of Sanitary Engineering. Sean is also the member of the ASSE Cross-Connection Control, Technical Committee. Sean is employed by IAPMO as the Vice President of Operations for the IAPMO Backflow Prevention Institute.