U.S. Department of Energy - Energy Efficiency and Renewable Energy 

Federal Energy Management Program 

Best Management Practice: Alternate Water Sources 

Many Federal facilities may have water uses that can be met with non-potable water from alternate 

water sources. Potentially available alternative water sources for Federal sources include municipalsupplied reclaimed water, treated gray water from on-site sanitary sources, and storm water. 

This page outlines alternate water source best management practices across: 

z Overview

{ Municipal-Supplied Reclaimed Water 

{ Treated Gray Water 

{ Rain Water 

{ Storm Water 

z Operations and Maintenance

{ Municipal Supplied Reclaimed Water 

{ Gray Water Recycling Systems 

z Retrofit and Replacement Options

{ Gray Water Recycling Systems 

{ Rain Water Harvesting 

z Resources 

z Case Studies 

Overview 

On-site alternative water sources are most economic if included in the original design. Common uses 

for these sources include landscape irrigation, ornamental pond and fountain filling, cooling tower 

make-up, and toilet and urinal flushing. 

Municipal-Supplied Reclaimed Water 

Municipal supplied reclaimed water has been treated and recycled for non-potable use. This water is 

often available at a significantly lower rate than potable water; however, use of reclaimed water is 

often restricted by local codes. 

Traditionally, centralized municipal sewage treatment facilities have been the primary source of water 

disposal for Federal facilities. However, heightened concerns about water supply availability have 

encouraged facility managers to consider on-site recycling of wastewater or gray water. 

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Treated Gray Water 

Sanitary gray water is water that is generated by bathroom sinks, showers, and clothes washing 

machines. These water sources can contain pathogens. Non-sanitary gray water is water generated 

by industrial processes or equipment such as reverse osmosis reject water and cooling tower 

condensate. These water sources can contain chemicals, minerals, and solids. 

In a typical gray water recycling system, water that would normally be discharged for municipal 

sewage treatment is collected, treated to remove suspended solids and contaminants, and reused. 

On-site wastewater recycling applications are currently found in states with persistent drought 

conditions. However, all arid, semiarid, and coastal areas that have experienced water shortages, as 

well as major urban areas where sewage treatment plants are overloaded and expansion is 

constrained, are potential candidates for on-site recycling. The recycled water is typically used as 

flush water for toilets and urinals, landscape irrigation, supply water for ornamental ponds, and 

make-up water for cooling towers. 

At its most basic, gray water treatment consists of removing suspended solids from the water. 

Filtering with no additional treatment may be applicable for rinse water from laundries or car washes 

and air handler condensate. At its most sophisticated, treatment may consist of biological treatment 

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with membrane filtration, activated carbon, and ultraviolet light or ozone disinfection to destroy 

pathogens. The basic gray water system includes storage tanks, color-coded piping, filters, pumps, 

valves, and controls. 

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Rain Water 

Rain water harvesting captures, diverts, and stores rain water for later use. Captured rain water is 

often used in landscaping, because the water is free of salts and other harmful minerals and does not 

have to be treated. It is also useful in attracting and providing water for wildlife. Rain water 

harvesting can also help prevent flooding and erosion, turning storm water problems into water 

supply assets by slowing runoff and allowing it to soak into the ground. Reducing run-off also helps 

reduce contamination of surface water with sediments, fertilizers, and pesticides in rainfall run-off. 

Rain water can be collected in cisterns and used with little or no treatment for a variety of nonpotable purposes. The major components of a rain water harvesting system include: 

z Catchment area/roof or surface upon which the rain falls 

z Gutters and downspouts to carry the water to storage 

z Leaf screens to remove debris 

z Cisterns/storage tanks to store the harvested rain water 

z Conveyances to deliver the stored water either by gravity or pump 

z Water treatment system to settle, filter, and disinfect the water, if required 

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Storm Water 

Like rain water, storm water can be harvested and reused for washdown, cooling tower make-up or 

process water, dust suppression, and vehicle washing. Storm water harvesting differs from rain water 

harvesting as the runoff is collected from drains or creeks, rather than roofs. The characteristics of 

storm water harvesting and reuse schemes vary considerably between projects, but most schemes 

include collection, storage, treatment, and distribution. 

Storm water is generally collected from a drain, creek, or pond and then stored temporarily in dams 

or tanks to balance supply and demand. Storage can be on-line (constructed on the creek or drain) or 

off-line (constructed some distance from the creek or drain). Captured water is typically treated to 

reduce pathogens and pollution levels through the use of constructed wetlands, sand filters, and 

disinfection techniques including chlorine, ultraviolet radiation, and membrane filtration. The degree 

of treatment required depends on the proposed use and the level of public exposure. 

Urban storm water harvesting and reuse is a relatively new field of water management and most of 

the projects constructed to date have been pilot projects in drought areas. 

Successful storm water harvesting and reuse plans need specialist input from a number of areas, 

including storm water management, water supply management, environmental management, and 

public health. The potential limitations and disadvantages to storm water harvesting and reuse 

include variable rainfall patterns, environmental impacts of storages, potential health risks, and high 

relative unit costs of treated storm water. Although this is not a practice that would be feasible at 

many Federal facilities, storm water harvesting and reuse is an emerging practice that may be useful 

in specific situations. 

To develop an efficient and successful reclaimed water project you must have a reliable source of 

wastewater of adequate quantity and quality to meet your non-potable water needs. These projects 

are economically more viable when: 

z The cost of water is high 

z There is a lack of high-quality freshwater supply 

z Reuse is the most cost-effective way to dispose of wastewater effluent 

z There are local policies that encourage the use of reclaimed water, or water efficiency 

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Operation and Maintenance Options 

To maintain water efficiency in operations and maintenance, Federal agencies should: 

z Identify potential non-potable water use while reviewing current water use practices. The use 

of non-potable water is generally most cost-effective when included in the design of new 

facilities. 

z Consult with experts in the field. Your first resource should be local or headquarters engineers, 

but do not rule out input from contractors or other Government agencies. 

z Facilities using alternative on-site water sources must comply with all applicable backflow 

prevention requirements. 

Municipal Supplied Reclaimed Water 

z Municipal supplied reclaimed water pipes must be color coded with purple tags or tape 

according to standards set by the American Water Works Association to minimize crossconnection problems. 

z Signs should be used liberally to indicate that reclaimed water is non-potable. Place them in 

public places such as in front of a fountain and on valves, meters, and fixtures. 

z Keep the pressure of reclaimed water 10 psi lower than potable water mains to prevent 

backflow and siphonage in case of accidental cross-connection. 

z Run reclaimed water mains at least 12 inches lower in elevation than potable water mains and 

horizontally at least five feet away. 

z Review the quality of reclaimed water to ensure there will be no harmful effects, such as salt 

buildup, from long-term use. 

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Gray Water Recycling Systems 

z The pathogenic organisms in sanitary gray water must not come into contact with either 

humans or animals. This can be accomplished by treating the water to eliminate pathogens or 

avoiding their introduction into water by not mixing sanitary gray water with any potable 

water source. Human exposure can be prevented by not collecting or storing it in an open 

container. 

z Sanitary gray water used for irrigation should not be applied through a spraying device, but 

rather injected directly into the soil through drip irrigation. Drip irrigation allows you to receive 

the benefits of using recycled water and at the same time avoid contaminating animals, 

humans, and edible plants. 

z If you install a gray water recycling system, consider using biodegradable cleaning products 

that do not contain sodium, chlorine, or boron. Cleaning products that contain high chemical 

levels may make their way into the gray water recycling system and could poison plants or 

damage soil through the buildup of inorganic salts. 

z Rain or excessive irrigation could cause ground saturation and result in pools of gray water on 

the surface. To help eliminate this situation, turn the gray water system off and divert the 

gray water to the sanitary sewer line during rainy periods. 

z Maintenance programs for a gray water system must include the following steps, all of which 

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must be performed regularly: 

{ Inspecting the system for leaks and blockages 

{ Cleaning and replacing the filter bimonthly 

{ Replacing the disinfectant 

{ Ensuring that controls operate properly 

{ Periodically flushing the entire system 

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Retrofit and Replacement Options 

The following retrofit and replacement options help Federal agencies implement gray water recycling 

systems and rain water harvesting: 

Gray Water Recycling System 

z The use of on-site wastewater recycling systems should be considered when constructing new 

buildings. Even though many of these systems are costly to purchase, the payback period in 

savings from discharging less wastewater can be as little as 10 years or less. 

z Gray water systems must be installed in accordance with local plumbing codes and by 

professional, licensed plumbing contractors. Installing a gray water system requires the 

retrofitting of existing plumbing and all alterations to the plumbing system must be approved 

by local authorities. 

z All counties and cities that permit gray water recycling require building inspections to inspect 

sites and, after the installation, verify compliance and proper operation of the gray water 

system. 

z Local authorities may require that gray water supply systems be clearly distinguished from 

potable water supplies. Methods of doing so include extensive labeling of the system or the 

use of different piping materials for the different systems. All gray water outlets must be 

clearly labeled to indicate that they dispense non-potable water. Local codes may also require 

marking gray water supplies by adding biodegradable dye. Additionally, backflow preventers 

also must be installed to ensure the proper separation of potable water and gray water supply 

system. 

z For buildings with slab foundations, recoverable gray water may be limited to washing 

machine discharge because most drain pipes, such as for sinks, are buried beneath the slab 

and thus not easily accessible without a significant additional expense. 

z For buildings with perimeter foundations, gray water may be recoverable from most sources 

due to accessibility to piping from crawl spaces. 

z Depending on the gray water source, application, recycling scheme, and economics, one gray 

water treatment method (e.g., media filtration, collection and settling, biological treatment 

units, reverse osmosis, sedimentation/filtration, physical/chemical treatment) may be more 

appropriate than another. 

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Rain Water Harvesting 

z Rain water collection and distribution systems can be incorporated into almost any existing 

site, although it is easier to incorporate them into new construction. 

z According to The Texas Manual on Rain Water Harvesting, you can collect 600 gallons of water 

per inch of rain per 1,000 square feet of catchment area. To determine how much water you 

could collect in a year: 

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Content Last Updated: 08/02/2012 

{ Calculate the roof catchment area 

{ Multiply the collection area in square feet by 0.6 gallons per square foot per inch of 

rain times the collection factor (which measures your collection efficiency; 80% or 0.8, 

would be a good efficiency) 

{ Times the average rainfall 

{ Divide this figure by 365 to get your daily collection figure 

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Resources 

The following resources provide guidance on water best management practices. 

z Methodology for Use of Reclaimed Water at Federal Locations : Guidelines to help 

Federal agencies use reclaimed water as part of Executive Order 13514 and other Federal 

water regulations. 

z Air Force Water Conservation Guidebook : Resource developed by the Air Force Civil 

Engineer Support Agency to assist base-level personnel in reducing potable water usage 

through life-cycle, cost-effective water efficiency programs. 

z Military Handbook: Water Conservation : Military guide on maximizing the efficient use 

of water resources to support military options and lessen demands placed upon existing water 

supplies. 

z General Services Administration Water Management Guide : Comprehensive approach 

for facility managers explaining new water conservation requirement under Executive Order 

13123. 

z A Water Conservation Guide for Commercial, Institutional, and Industrial Users : 

Overview of water conservation strategies and benefits presented by the New Mexico Office of 

the State Engineer. 

z Laboratories for the 21st Century: Voluntary partnership program between the 

Department of Energy and Environmental Protection Agency dedicated to improving the 

environmental performance of U.S. laboratories. 

z Water Efficiency Guide for Laboratories : Guide to water efficiency as part of a larger 

series of efficiency best practices for laboratories. 

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Case Studies 

Severe drought caused the U.S. Environmental Protection Agency (EPA) to address water 

conservation and management for their Science and Ecosystem Support Division. The plan aimed to 

reduce potable water usage through an air handler condensate recovery project . 

The U.S. Army's Fort Carson has built a successful and award-winning water conservation program

through a series of initiatives that avoid using potable water. The program involves an innovative 

approach to utilizing alternative sources of water, water reclamation, and recycling. 

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