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Managing Wet Weather with 

Green Infrastructure

Municipal Handbook

Rainwater Harvesting Policies
Managing Wet Weather with Green Infrastructure 

Municipal Handbook 

Rainwater Harvesting Policies 

prepared by 

Christopher Kloss 

Low Impact Development Center 

The Municipal Handbook is a series of documents 

to help local officials implement green infrastructure in their communities.

December 2008 

EPA-833-F-08-010 

Front Cover Photos 

Top: rain garden; permeable pavers; rain barrel; 

planter; tree boxes. 

Large photo: cisterns in the Wissahickon 

Charter School’s Harmony Garden in 

Philadelphia 
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Rainwater Harvesting Policies 

Introduction

From the last half of the 20th century, the U.S. has enjoyed nearly universal access to abundant supplies of 

potable water. But as witnessed by the recent serious and sustained droughts in the Southeast and 

Southwest, this past luxury is not something that can be expected for the long term. Future population

growth will exert more demand on water systems while climate change is predicted to decrease available

supplies because of decreased snow pack and drier regional climatic patterns. The U.S. has been 

identified as a country that faces imminent water shortages and a Government Accountability Office 

(GAO) survey found that water managers in 36 states anticipate water shortages during the first two 

decades of this century.1 These challenges will require a more sustainable approach to using water 

resources, looking at not only how much water is used, but also the quality of water needed for each use. 

The overwhelming majority of the water used in the U.S. comes from freshwater supplies of surface and 

groundwater. Water extracted for public systems is treated to potable standards as defined by the Safe

Drinking Water Act. Access to high quality water has greatly benefited public health, but it has also 

resulted in our current system that utilizes potable water for virtually every end use, even when lesser 

quality water would be sufficient. In addition to conservation methods, using alternative sources of water 

will be necessary for more efficient use of water resources. 

Rainwater harvesting, collecting rainwater from impervious surfaces and storing it for later use, is a

technique that has been used for millennia. It has not been widely employed in industrialized societies 

that rely primarily on centralized water distribution systems, but with limited water resources and 

stormwater pollution recognized as serious problems and the emergence of green building, the role that

rainwater harvesting can play for water supply is being reassessed. Rainwater reuse offers a number of

benefits.2

• Provides inexpensive supply of water; 

• Augments drinking water supplies; 

• Reduces stormwater runoff and pollution; 

• Reduces erosion in urban environments; 

• Provides water that needs little treatment for irrigation or non-potable indoor uses; 

• Helps reduce peak summer demands; and 

• Helps introduce demand management for drinking water systems. 

Rainwater harvesting has significant potential to provide environmental and economic benefits by 

reducing stormwater runoff and conserving potable water, though several barriers exist that limit its 

application. The U.S. uses more water per capita than any other country, with potable water delivered for 

the majority of domestic and commercial applications. Typical domestic indoor per capita water use, 

shown in Table 1, is 70 gallons per day (gpd); however outdoor water use can constitute 25% to 58% of 

overall domestic demand, increasing per capita domestic use up to 165 gpd. 
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Table 1. Typical Domestic Daily per Capita Water Use.3

Use Gallons per Capita % of Daily Total 

Potable indoor uses 

• Showers 

• Dishwashers 

• Baths 

• Faucets 

• Other uses, leaks 

11.6 

1.0 

1.2 

10.9 

11.1 

7.0% 

0.6% 

0.8% 

6.6% 

6.7% 

Subtotal 35.8 21.7% 

Non-potable indoor uses 

• Clothes washers 

• Toilets 

15.0 

18.5 

9.1% 

11.2% 

Subtotal 33.5 20.3%

Outdoor uses 95.7 58.0% 

While potable water is used almost exclusively for domestic uses, almost 80% of demand does not require 

drinkable water. Similar trends exist for commercial water use. Table 2 provides examples of daily 

commercial water usage. 

Table 2. Typical Daily Water Use for Office Buildings and Hotels.4

Use 

Office Buildings 

% of Daily Total 

Hotels 

% of Daily Total 

Potable indoor uses 

Showers 

• Faucets 

• Kitchen 

• Other uses 

--- 

1% 

3% 

10% 

27% 

1% 

10% 

19% 

Subtotal 14% 57% 

Non-potable indoor uses 

• Toilets/urinals 

• Laundry 

• Cooling 

25% 

--- 

23% 

9% 

14% 

10% 

Subtotal 48% 33% 

Outdoor uses 38% 10% 

Both the domestic and commercial water use statistics show that potable water is often being utilized for 

end uses that could be satisfied with lesser quality water. The statistics also indicate that nearly all water 

is used in a one-time pass through manner, with little attempt at reuse. Rainwater harvesting offers an 

alternative water supply that can more appropriately match water use to the quality of water supplied.

Rainwater harvesting systems typically divert and store runoff from residential and commercial roofs. 

Often referred to as ‘clean’ runoff, roof runoff does contain pollutants (metals or hydrocarbons from 

roofing materials, nutrients from atmospheric deposition, bacteria from bird droppings), but they are 

generally in lower concentrations and absent many of the toxics present in runoff from other impervious 

surfaces. Installing a rainwater collection system requires diverting roof downspouts to cisterns or rain 

barrels to capture and store the runoff. Collection containers are constructed of dark materials or buried to 

prevent light penetration and the growth of algae.5 From the storage container, a dual plumbing system is 

needed for indoor uses and/or a connection to the outdoor irrigation system. 

Regulations

Although a few states and local jurisdictions have developed standards or guidelines for rainwater 

harvesting, it is largely unaddressed by regulations and codes. Neither the Uniform Plumbing Code 
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(UPC) nor International Plumbing Code (IPC) directly address rainwater harvesting in their potable or 

stormwater sections. Other reuse waters are covered by codes. The UPC’s Appendix J addresses 

reclaimed water use for water closets and urinals and the IPC’s Appendix C addresses graywater use for

water closets and urinals along with subsurface irrigation.6 Both sections focus on treatment requirements, 

measures necessary to prevent cross-contamination with potable water, and appropriate signage and 

system labeling. However, because of a general lack of specific rainwater harvesting guidance some 

jurisdictions have regulated harvested rainwater as reclaimed water, resulting in more stringent 

requirements than necessary. These issues have led to confusion as to what constitutes harvested 

rainwater, graywater, or reclaimed water.7

The confusion among waters for reuse and the 

lack of uniform national guidance has resulted 

in differing use and treatment guidelines among 

state and local governments and presents an 

impediment to rainwater reuse. Texas promotes 

harvested rainwater for any use including 

potable uses provided appropriate treatment is 

installed; Portland, like many other 

jurisdictions, generally recommends rainwater 

use to the non-potable applications of irrigation, 

hose bibbs, water closets, and urinals. 

To develop general or national guidance for 

rainwater harvesting, several factors must be 

considered. While potable use is possible for 

harvested rainwater, necessary on-site treatment 

and perceived public health concerns will likely limit the quantity of rainwater used for potable demands. 

Irrigation and the non-potable uses of water closets, urinals and HVAC make-up are the end uses that are 

generally the best match for harvested rainwater. A lesser amount of on-site treatment is required for

these uses and, as seen from the use statistics presented above, these uses constitute a significant portion 

of residential and commercial demand. Focusing harvested rainwater on irrigation and selected nonpotable indoor uses can significantly lower demand while allowing a balance and public comfort level 

between municipal potable water and reused rainwater. 

 Guidance for the reuse of harvested stormwater will be similar to reclaimed water and graywater but will 

differ because of lower levels of initial contamination and targeted end uses. The primary concerns of

indoor rainwater reuse are cross-contamination of the potable supply and human contact with bacteria or 

pathogens that may be present in the collected rainwater. Portland’s Rainwater Harvesting One and Two 

Family Dwelling Specialty Code provides a good example 

of specific rainwater reuse stipulations. Although the code 

doesn’t address multi-family residential or non-residential 

applications, rainwater reuse is permitted for these facilities, 

but due to the unique design of each system, commercial 

reuse systems are considered on a case by case basis. In 

addition, multi-family residential units and sleeping portions 

of hotels are allowed to use rainwater for irrigation only; 

non-residential buildings are permitted to use rainwater for 

irrigation, water features, water closets and urinals. In these 

applications, water provided for water closets and urinals 

must be treated with filters and UV and/or chlorinating.9

UPC Definitions – Waters for Reuse8

• Graywater – untreated wastewater that has not come in 

to contact with black water (sewage). Graywater 

includes used water from bathtubs, showers, lavatories, 

and water from clothes washing machines. 

• Reclaimed water – water treated to domestic 

wastewater tertiary standards by a public agency 

suitable for a controlled use, including supply to water 

closets, urinals, and trap seal primers for floor drains 

and floor sinks. Reclaimed water is conveyed in purple 

pipes (California’s purple pipe system is one of the 

better known water reclamation systems). 

• Harvested rainwater – stormwater that is conveyed 

from a building roof, stored in a cistern and disinfected 

and filtered before being used for toilet flushing. It can 

also be used for landscape irrigation. 

Tucson Rainwater 

Harvesting Requirements 

Tucson, Arizona became the first city in the 

country to require rainwater harvesting for 

landscaping use. Beginning June 1, 2010, 

50% of a commercial property’s irrigation 

water must be supplied from rainwater. In 

addition to cisterns, the regulations allow 

berms and contoured slopes to be used to 

direct rainwater to trees and landscaped 

areas. 
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Portland’s code permits rainwater reuse for 

potable uses at family dwellings only 

through an appeals process. In addition, 

rainwater used only for outdoor irrigation is 

not covered by the code and needs no 

treatment prior to use. Acceptable indoor 

non-potable uses are hose bibbs, water 

closets, and urinals. The code illuminates 

several important issues that need to be 

considered when developing rainwater 

harvesting code. 

• Water quality – Water quality and 

its impact on human health is a 

primary concern with rainwater 

harvesting. This issue is comprised 

of two components: end use of the 

rainwater and treatment provided. 

Rainwater used for residential 

irrigation (on the scale of rain 

barrel collection) does not typically 

require treatment. Commercial 

applications and non-potable 

indoor uses require treatment but 

the type of use will determine the 

extent of treatment. Each 

jurisdiction will need to assess the 

level of treatment with which it is 

comfortable, but limiting rainwater 

reuse to water closets, urinals and 

hose bibbs presents little human 

health risk. Each system will 

require some level of screening and 

filtration to prevent particles and 

debris from traveling through the 

plumbing system, and most 

jurisdictions require disinfection 

with UV or chlorination because of 

bacterial concerns. Table 3 

provides an example of minimum 

water quality guidelines and 

suggested treatment methods for collected rainwater. 

A review of treatment standards among various jurisdictions shows a wide range of 

requirements from minimal treatment to reclaimed water standards. A recent memorandum of 

understanding from the City and County of San Francisco allows rainwater to be used for toilet 

flushing without being treated to potable standards. Texas requires filtration and disinfection for 

non-potable indoor uses, and Portland requires filtration for residential non-potable indoor uses, 

but requires filtration and disinfection for multi-family and commercial applications. Treatment 

requirements ultimately come down to risk exposure with risk of bacterial exposure determining 

the most stringent levels of treatment. However, San Francisco’s Memorandum or 

Understanding indicates a belief in a low exposure risk with rainwater when used for toilet 

flushing. Likewise, testing conducted in Germany demonstrated that the risk of E. coli contact 

with the human mouth from toilet flushing was virtually non-existent, resulting in the 

Excerpts of General Requirements 

Portland Rainwater Harvesting Code Guide 

General 

• Harvested rainwater may only be used for water 

closets, urinals, hose bibbs, and irrigation. 

• Rainwater can only be harvested from roof surfaces. 

• The first 10 gallons of roof runoff during any rain event 

needs to be diverted away from the cistern to an Office 

of Planning & Development Review (OPDR) approved 

location. 

Rainwater Harvesting System Components 

• Gutters – All gutters leading to the cistern require leaf 

screens with openings no larger than 0.5 inches across 

their entire length including the downspout opening. 

• Roof washers – Rainwater harvesting systems 

collecting water from impervious roofs are required to 

have a roof washer for each cistern. Roof washers are 

not required for water collected from green roofs or 

other pervious surfaces. The roof washer is required to 

divert at least the first 10 gallons of rainfall away from 

the cistern and contain 18 inches of sand, filter fabric, 

and 6 inches of pea gravel to ensure proper filtration. 

• Cisterns – Material of construction shall be rated for 

potable water use. Cisterns shall be able to be filled 

with rainwater and the municipal water system. Crosscontamination of the municipal water system shall be 

prevented by the use of (1) a reduced pressure 

backflow assembly or (2) an air gap. Cisterns shall be 

protected from direct sunlight. 

• Piping – Piping for rainwater harvesting systems shall 

be separate from and shall not include any direct 

connection to any potable water piping. Rainwater 

harvesting pipe shall be purple in color and labeled 

“CAUTION: RECLAIMED WATER, DO NOT DRINK” 

every four feet in length and not less than once per 

room. 

• Labeling – Every water closet or urinal supply, hose 

bibb or irrigation outlet shall be permanently identified 

with an indelibly marked placard stating: “CAUTION:

RECLAIMED WATER, DO NOT DRINK.” 

• Inspections – Inspections are required of all elements 

prior to being covered. 

• Maintenance – Property owner is responsible for all 

maintenance. 
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recommendation that special disinfection measures were unnecessary for rainwater dedicated to 

non-potable uses.10

The level of treatment required by each municipality can influence the number of harvesting 

systems installed. Filtration and disinfection are not expensive treatment requirements but each 

treatment requirement adds a cost to the system. Simplifying the treatment requirements when 

there is not a threat to public health lowers the cost for private entities to install systems and 

encourages broader adoption of the practice. 

• Cross-contamination – Cross-contamination of the potable water system is a critical concern for 

any water reuse system. Cross-contamination measures for rainwater reuse systems will be 

similar to those for reclaimed and graywater systems. When rainwater is integrated as a 

significant supply source for a non-potable indoor use, a potable make-up supply line is needed 

for dry periods and when the collected rainwater supply is unable to meet water demands. The 

make-up supply to the cistern is the point of greatest risk for cross-contamination of the potable 

supply. Codes will require a backflow prevention assembly on the potable water supply line, an 

air gap, or both. In addition to backflow prevention, the use of a designated, dual piping system 

is also necessary. Purple pipes, indicating reused water, are most often used to convey rainwater 

and are accompanied by pipe stenciling and point-of-contact signage that indicates the water is 

non-potable and not for consumption. 

• Maintenance and inspection – The operation and maintenance of rainwater harvesting systems 

is the responsibility of the property owner. Municipal inspections occur during installation and 

inspections of backflow prevention systems are recommended on an annual basis. For the 

property owner, the operation of a rainwater harvesting system is similar to a private well. 

Especially for indoor uses annual water testing to verify water quality is recommended as well 

as regular interval maintenance to replace treatment system components such as filters or UV 

lights. The adoption and use of rainwater harvesting systems will add to the inspection 

responsibilities of the municipal public works department, but the type of inspection, level of 

effort, and documentation required will be similar to those of private potable water systems and 

should be readily integrated into the routine of the inspection department. 

Table 3. Minimum Water Quality Guidelines and Treatment Options for Stormwater Reuse.11

Use 

Minimum Water Quality 

Guidelines Suggested Treatment Options 

Potable indoor uses • Total coliforms – 0 

• Fecal coliforms – 0 

• Protozoan cysts – 0 

• Viruses – 0 

• Turbidity < 1 NTU 

• Pre-filtration – first flush diverter 

• Cartridge filtration – 3 micron 

sediment filter followed by 3 micron 

activated carbon filter 

• Disinfection – chlorine residual of 0.2 

ppm or UV disinfection 

Non-potable indoor uses • Total coliforms < 500 cfu per 

100 mL 

• Fecal coliforms < 100 cfu per 

100 mL 

• Pre-filtration – first flush diverter 

• Cartridge filtration – 5 micron 

sediment filter 

• Disinfection – chlorination with 

household bleach or UV disinfection 

Outdoor uses N/A Pre-filtration – first flush diverter 

*cfu – colony forming units 

*NTU – nephelometric turbidity units 

Institution Issues and Barriers

Although stormwater reuse offers environmental and economic benefits, its use has remained relatively 

limited. This is caused by a number of perceived and actual barriers. The high rate of water consumption 

in the U.S. is coupled with water cost rates that are among the lowest. For example, U.S. water use is

approximately twice that of Europe, but the annual cost of household water bills are roughly equal. The 

cost of water in the U.S. ranges from $0.70 to $4 per thousand gallons, with the national average cost
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slightly more than $2 for a thousand gallons. Price, therefore, creates little incentive for conservation or 

the use of alternative sources.12

Residential rain barrels are an inexpensive and easy retrofit that reduces stormwater 

runoff and provides irrigation water. Photo at left: District of Columbia Water & Sewer 

Authority; Photo at right: Ann English.

San Francisco Rainwater Harvesting MOU 

In 2008, San Francisco’s Public Utilities Commission (SFPUC), Department of Building Inspection (DBI), and 

Department of Public Health (DPH) signed a Memorandum of Understanding for the permitting requirements for 

rainwater harvesting systems located within the City and County of San Francisco. The MOU encourages rainwater 

harvesting and its reuse for non-potable applications without requiring treatment to potable water standards. It also 

defines the roles of the participating agencies. From the MOU: 

• The SFPUC will create and distribute guidance and material on rainwater harvesting. The material will cover 

system design, system components, allowable uses, owner responsibilities, and permitting requirements. The 

SFPUC will encourage all rainwater harvesters to notify the SFPUC with the design specifications of their 

systems for research purposes. 

• DBI will issue permits for construction of properly designed rainwater harvesting systems for non-potable 

uses that meet the minimum criteria described in the MOU and in guidance materials prepared by the 

SFPUC. DBI will be responsible for review of permit applications and inspection of rainwater harvesting 

systems that require permits. 

• DPH will review rainwater harvesting projects that propose any residential indoor uses of rainwater other than 

toilet flushing to assure the protection of public health. 

It also stipulates that system design, maintenance, and use are the responsibility of the system owner. 

The MOU classifies rain barrels and cisterns and defines the allowable uses of harvested rainwater. Water from rain 

barrels may be used for irrigation and vehicle washing; it is prohibited to connect rain barrels to indoor or outdoor 

plumbing. Water from cisterns connected to indoor plumbing may be used for irrigation, vehicle washing, heating and 

cooling, and toilet flushing. If a cistern is not connected to indoor plumbing it cannot be used for toilet flushing. 

The MOU also includes safety and maintenance requirements, required system components, labeling requirements, 

and DBI permit requirements. 
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To better manage natural resources and water infrastructure, EPA has advocated four pillars of 

sustainable infrastructure, one of which is full cost pricing of water. Full cost pricing would result in 

water rates that reflect the entire suite of costs associated with water delivery: past, present, and future 

capital costs and operations and maintenance. Full cost pricing would ideally also include the external 

costs associated with the environmental damage and resource depletion created by water use.13, 14 

However, user fees and other funding sources are insufficient in 29% of water utilities to cover the cost of 

providing service, let alone including external costs.15 Insufficient pricing is a significant barrier to 

collection and reuse. 

Water needed for sanitation, cleaning, and cooking is less 

responsive to price than discretionary uses such as

landscaping, but overall, water generally displays inelastic 

demand. A 10% increase in domestic prices decreases demand 

2 to 4%; a 10% increase in commercial prices decreases 

demand 5 to 8%.16 While studies show that price has limited 

effect on demand, they also do not consider the option of a 

low-cost alternative source of water. Increased prices may not 

significantly diminish water use, but may be sufficient to 

encourage the use of lower cost alternatives. When faced with 

sufficiently priced potable water, the investment in a low cost 

alternative that provides continued savings becomes

increasingly favorable. 

Regulations and codes also inhibit rainwater collection. 

Plumbing codes have been identified as a common barrier. 

Whether they make no provisions for rainwater reuse or 

require downspouts to be connected to the stormwater collection system, thereby eliminating the 

possibility of intervening to intercept roof runoff, code changes are often a necessary first step to enabling 

rainwater harvesting. Other regulations complicate the implementation of rainwater harvesting. Western

water rights and the doctrine of “first in time, first in line” access to water can present a barrier to 

rainwater harvesting. Colorado interprets its Western water rights laws as prohibiting rainwater 

harvesting. The state’s interpretation that cisterns and rain barrels prevent runoff from reaching rivers and 

thereby decrease a downstream user’s allotted water right has been questioned, but it currently prohibits 

rainwater capture and reuse. 

Rainwater Harvesting in the West 

Western water rights can be an impediment to rainwater harvesting efforts because the doctrine of prior appropriation 

has created ambiguity about the legality of intercepting and storing rainwater. In the strictest interpretation, diverting 

rainwater to a collection system is a taking of a water previously appropriated. 

This issue has been overlooked for many community rain barrel initiatives, because the individual storage units are 

relatively small. The City of Seattle, however, obtained a citywide water-right permit to ensure the legality of water 

harvesting efforts. 

State legislation may ultimately be necessary to ensure the legality of rainwater harvesting and establish the upper 

capacity limit for rainwater systems. Any efforts should fully assess the watershed impacts of rainwater harvesting 

efforts. Colorado law, for instance has assumed that all rainfall eventually reaches groundwater or surface waters and 

is therefore appropriated. In the dry regions of the state, however, a study has found that the majority of rainfall on 

undeveloped lands is lost to evaporation and transpiration and only a small fraction actually reaches surface waters. 

Likewise, rainwater harvesting is a water conservation practice which will reduce the overall withdrawal and use of 

water, making a greater quantity of water available for downstream users. Harvested rainwater used for irrigation or 

other outdoor uses reapplies the water in a manner similar to normal precipitation. Rainwater used for non-potable 

indoor uses is collected in the sanitary system and eventually returned to receiving streams and available for 

downstream use. 

Albuquerque-Bernalillo County Building 

Standards 

In 2008, the Water Utility Authority of 

Albuquerque-Bernalillo County instituted 

new standards that require rainwater 

harvesting systems for new homes. 

Buildings larger than 2,500 square feet are 

required to have a cistern and pump, while 

smaller buildings can use cisterns, rain 

barrels, or catchment basins. All rainwater 

harvesting systems need to capture the 

runoff from at least 85% of the roof area. 

The standards also include a requirement 

for high efficiency toilets and prohibitions 

against installing turf on slopes steeper 

than 5:1 and sprinkler irrigating areas 

smaller than 10 feet in any dimension. 
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Energy and Climate

In addition to the natural resources impacts that water use imparts, water collection, treatment, and 

distribution has energy and climate consequences. The connection between water and energy is often 

overlooked but the process of extracting water from surface or groundwater supplies, bringing it to 

treatment facilities, treating it to drinking water standards, and delivering it to residential and commercial 

customers expends energy primarily because of pumping and treatment costs. The water sector consumes 

3% of the electricity generated in the U.S. and electricity accounts for approximately one-third of utilities’ 

operating costs.17 Reducing potable water demand by 10% could save approximately 300 billion kilowatthours of energy each year.18 Water reuse systems, like rainwater harvesting, supplant potable water and 

reduce demand. The reduced water demand provided by rainwater harvesting systems translates directly 

to energy savings. Table 4 presents estimates of the energy required to deliver potable water to 

consumers. 

Table 4. Estimated Energy Consumption for 

Water Treatment and Distribution.19

Activity 

Energy Consumption 

kWh/MG 

Supply and conveyance 150 

Water Treatment 100 

Distribution 1,200 

Total 1,450 

Decreasing potable water demand by 1 million gallons can reduce electricity use by nearly 1,500 kWh. 

An inch of rainfall produces 600 gallons of runoff per 1,000 square feet of roof. Coordinated residential 

applications and large-scale non-residential rainwater harvesting systems offer an alternative method of 

reducing energy use. 

Limiting energy demand is significant but the impact that decreased energy demand has on carbon 

dioxide emissions is critical. Carbon dioxide emissions associated with electricity generation vary 

according to the fossil fuel source. Rough estimates suggest that reducing potable water demand by 1 

million gallons can reduce carbon dioxide emissions 1 to 11⁄2 tons when fossil fuels are used for power 

generation (Table 5). 

Table 5. Carbon Dioxide Emissions from Electric Power Generation.20

Fuel Type 

CO2 Output Rate 

Pounds CO2/kWh 

CO2 Output per MG Water 

Delivered (x 1,450 kWh) 

Coal 2.117 3,070 lbs 

Petroleum 1.915 2,775 lbs 

Natural gas 1.314 1,905 lbs 

The carbon reductions associated with rainwater harvesting are admittedly not on the order of magnitude 

required to significantly impact climate change. However, the connection between potable water use and

energy demand is important to recognize in the broader context of sustainable water management. It is 

critical to assess water use not only from a resource availability and protection standpoint, but also with 

the aim of improving overall sustainability of which energy is a critical component. As municipalities are 

faced with the anticipated CO2 reductions that will be required over the coming decades, decreased 

potable water demand (along with other measures such as increased energy efficiency and conservation) 

represent the “low hanging fruit” that may provide the quickest and easiest reductions. Rainwater 

harvesting along with graywater and reclaimed water reuse represent an integrated water management 

approach that can not only limit contributions to climate change, but also protect and conserve limited 

water resources developing resiliency to the uncertain effects of climate change. 
9

Conclusions and Recommendations

Encouraging rainwater harvesting and reuse requires enabling the practice through codes and regulations 

and providing incentives. State or municipal codes need to address public health concerns by stipulating 

water quality and cross-contamination requirements. Similar to reclaimed and graywater, specific 

rainwater harvesting codes need to be developed. Codes should establish acceptable uses for rainwater 

and corresponding treatment requirements. Disinfection of rainwater for reuse has been the standard, but 

recent research and policies should encourage jurisdictions to evaluate lesser requirements for nonpotable uses in water closets and urinals. The simplification of the on-site treatment process and 

associated cost savings could broaden the use of rainwater harvesting without increasing exposure risks. 

In addition to code development, incentives for 

rainwater harvesting should be instituted. The 

incentives should recognize that rainwater is a 

resource and that the use of potable water carries 

and environmental and economic cost. Current 

water policies and rates do not promote 

sustainability, with a structure that inadequately 

accounts for the value of water and does not 

promote conservation. Municipalities should review 

their water rates to see if they appropriately account 

for the full cost of water. Pricing alternatives such 

as increasing block rates, which increase the price

of water with increased use, create an incentive to

conserve potable water. An increased price of 

potable water would encourage investment in 

rainwater harvesting systems because they offer a 

long-term inexpensive supply of water after the 

initial capital investment. The combined actions of 

establishing certain requirements for rainwater 

harvesting systems and increasing the currently 

underpriced cost of water creates a complementary 

system that can encourage the use of alternative 

water sources. 

Commercially sized cistern at the Chicago Center for 

Green Technology. Photo: Abby Hall, EPA.
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Considerations when Establishing a Municipal Rainwater Harvesting Program 

1. Establish specific codes or regulations for rainwater harvesting 

• Building and plumbing codes are largely silent on rainwater harvesting. Consequently, graywater 

requirements are often used to govern rainwater harvesting systems, resulting in requirements that are more 

stringent than necessary. Codes should define rainwater harvesting and establish its position as an 

acceptable stormwater management/water conservation practice. 

2. Identify acceptable end uses and treatment standards 

• Each municipality will need to consider and identify acceptable uses for harvested rainwater and the required 

treatment for specified uses. Rainwater is most commonly used for non-potable applications and segregated 

by indoor and outdoor uses. 

 Typical outdoor uses: 

1. Irrigation; and 

2. Vehicle washing. 

 Typical indoor uses: 

1. Toilet flushing; 

2. Heating and cooling; and 

3. Equipment washing. 

• Non-potable uses typically require minimal treatment. Outdoor uses normally need only prescreening to limit 

fouling of the collection system. Indoor non-potable uses do not necessarily require treatment beyond 

screening, although some municipalities have adopted a conservative approach and require filtration and 

disinfection prior to reuse. 

• Harvested rainwater can be used for potable applications although a special permitting process should be 

established to ensure that proper treatment (e.g., filtration and disinfection) is provided and maintained. 

3. Detail required system components 

• Jurisdictions often delineate between rain barrels and cisterns because of the size and potential complexity of 

the systems. Rain barrels collect relatively small quantities of water and generally only require mosquito 

prevention, proper overflow, and an outlet for outdoor uses. Cisterns can be 100 to several thousand gallons 

in size and may be connected to various indoor plumbing and mechanical systems. Needed system 

requirements include: 

 Pre-filtration – Filtration prior to the rain barrel or cistern should be provided to remove solids and debris. 

 Storage containers – Rain barrels and cisterns should be constructed of a National Sanitation 

Foundation approved storage container listed for potable water use. 

 Back-flow prevention – For cisterns that require a potable water make-up for operation, back flow 

prevention in the form of an air gap or backflow assembly must be provided. 

 Duel piping system – a separate piping system must be provided for harvested rainwater distribution. 

The pipe should be labeled and color coded to indicate non-potable water. Purple piping indicating 

reclaimed water is often used for rainwater harvesting systems. Cross connections with the potable 

water supply system are prohibited. 

 Signage – permanent signage should be provided at every outlet and point of contact indicating nonpotable water not for consumption. In addition, biodegradable dyes can be injected to indicate nonpotable water. 

4. Permitting 

• Rain barrels should not need to be permitted provided that they are installed correctly and direct overflow to a 

proper location. A permit application process should be instituted for cistern systems used for non-potable 

uses. If harvested rainwater is used for potable water, the collection and treatment system should be 

inspected and approved by the public health department. 

5. Maintenance 

• Adequate design and maintenance of the cistern and piping system is the responsibility of the cistern owner. 

6. Rates of reuse 

• For harvesting systems to be efficient stormwater retention systems, the collected rainwater needs to be used 

in a timely matter to ensure maximum storage capacity for subsequent rain events. Cistern systems generally 

supply uses with significant demands, ensuring timely usage of the collected water. Outreach and education 

is a critical component of rain barrel programs, however, because of the more episodic and less structured 

use of this collected water. Municipalities should inform homeowners of the steps needed to maximize the 

effectiveness of their rain barrels. Harvesting programs targeting susceptible combined sewer areas have 

used slow draw down of the rain barrels to delay stormwater release to the sewer system, yet ensure 

maximum storage capacity for subsequent rain events.
11

Case Studies

King Street Center, Seattle 

The King Street Center in Seattle uses rainwater for toilet flushing and irrigation. Rainwater from the 

building’s roof is collected in three 5,400 gallon cisterns. Collected rainwater passes through each tank 

and is filtered prior to being pumped to the building’s toilets or irrigation system through a separate 

piping system. When needed, potable makeup water is added to the cisterns. The collection and reuse 

system is able to provide 60% of the annual water needed for toilet flushing, conserving approximately

1.4 million gallons of potable water each year.21

The Solaire, Battery Park City, New York 

The 357,000 square foot, 27 floor building was the first high-rise residential structure to receive LEED®

Gold certification. The Solaire was designed to comply with Battery Park City’s progressive water and 

stormwater standards; more than 2 inches of stormwater must be treated on site to meet the standards. 

Rainwater is collected in a 10,000 gallon cistern located in the building’s basement. Collected water is 

treated with a sand filter and chlorinated according to New York City Standards prior to being reused for 

irrigating two green roofs on the building. Treated and recycled blackwater is used for toilet flushing and 

make-up water. Water efficient appliances and the rainwater and blackwater reuse system have decreased

potable water use in the building by 50%.22 Because of its innovative environmental features, the Solaire 

earned New York State’s first-ever tax credit for sustainable construction.23, 24

Philip Merrill Building, Annapolis, MD 

The Chesapeake Bay Foundation’s 

headquarters is a LEED® Version 1 Platinum 

certified building. Rainwater from the roof is 

collected in three exposed cisterns located 

above the entrance.25 Roof runoff passes 

through roof washers before entering the 

cisterns; following the cisterns the water is 

treated with a sand filter, chlorination, static 

mixer, and carbon filter prior to reuse. The 

building uses composting toilets, so the reused 

water is used for bathroom and mop sinks, gear 

washing, irrigation, fire suppression, and 

laundry. The building’s design allows for a 

90% reduction in potable water use with 73% 

of the water used within the building supplied 

by the cistern collection system.26, 27, 28

Alberici Corporate Headquarters, Overland, Missouri 

Alberici Corporation, a construction company, chose to relocate its corporate headquarters to a 14-acre 

site in the St. Louis suburbs in 2004. The site renovation included refurbishing a 150,000 square foot

former metal fabrication facility into a LEED® platinum certified office building. The building design 

includes a rainwater collection and reuse system. Rainwater is collected from 60% of the garage roof area 

and stored in a 38,000 gallon cistern. The collected water is filtered and chlorinated and used for toilet 

flushing and the building’s cooling tower. The stormwater reuse system saves 500,000 gallons of water 

each year, reducing potable water demand by 70%.29, 30

Lazarus Building, Columbus, Ohio 

After Federated Department Stores closed the 750,000 square foot retail store in 2002, it donated the 

building to the Columbus Downtown Development Corporation. The building renovation completed in 

2007 achieved LEED® Gold certification and the building’s largest tenant is Ohio EPA. The renovated 

building includes a rainwater collection and reuse system. The system makes use of an existing 40,000 

Cisterns at CBF headquarters. Photo: Chesapeake Bay 

Foundation.
12

gallon tank on the building’s roof and a new 50,000 gallon tank installed in the basement. The collected 

rainwater is used for toilet flushing, irrigation, and HVAC makeup. A biodegradable blue dye is added to 

the water used for toilet flushing to visually identify it as non-potable water. The system reduces potable 

water use in the building by several million gallons a year.31, 32 

Stephen Epler Hall, Portland State University 

PSU’s 62,500 square foot mixed-use student housing facility (classrooms and academic office space are 

located on the first floor) was completed in 2003 and is LEED® Silver Certified. The stormwater 

management system was designed to be engaging to the public; rain from the roofs of Epler Hall and 

neighboring King Albert Hall is diverted to several river rock “splash boxes” in the public plaza.33 The 

water then travels through channels in the plaza’s brick pavers to planter boxes where it infiltrates and is 

filtered before being collected in an underground cistern. UV light is used to treat the water prior to its 

reuse for toilet flushing in the first floor restroom and irrigation. Placards located in the water closets 

indicate that the non-potable toilet flushing water is not for consumption. The stormwater collection and 

reuse system conserves approximately 110,000 gallons of potable water annually, providing a savings of

$1,000 each year.34, 35

Natural Resources Defense Council’s Robert Redford Building, Santa Monica 

NRDC’s renovation of a 1920s-era structure in downtown Santa Monica achieved LEED® New 

Construction, Version 2 Platinum certification. The innovative water systems in the 15,000 square foot

building are a key component of the project’s 

sustainability. The plumbing system delivers 

potable water only to locations where drinking 

water is needed, such as faucets and showers. 

Water from the showers and sinks is collected in 

graywater collection tanks and treated on-site. The

treated graywater is reused for toilet flushing and

landscaping. Rainwater from the building is 

collected in outdoor cisterns, which were installed

beneath planters adjacent to the building. The 

collected rainwater is filtered prior to being added 

to the graywater collection tank as part of the water 

reuse system. The graywater/rainwater reuse 

system and high-efficiency features such as duelflush toilets, waterless urinals, and drought-tolerant 

plants reduce potable water demand by 60%. Each 

waterless urinal, for instance, saves 40,000 gallons 

of water each year.36

The City’s plumbing code complicated the 

installation of many of the building’s water 

features. The plumbing code prohibited waterless 

toilets or urinals, requiring a resolution that 

allowed the waterless urinals to be installed with 

water supply stubbed out behind the wall if needed 

for future use. The City is now seeking a change to

City Code to allow for waterless urinals to be installed without an available water supply. Similarly,

California’s graywater ordinance did not contain a provision for rainwater collection; an agreement was 

negotiated with the County Health Department after which the City’s Building and Safety Division agreed 

to sign off on the plans.37, 38 

Rainwater cistern at NRDC’s Santa Monica Office 

(inset photo after planter planting). Photo: NRDC.
13

 

1

 U.S. Government Accountability Office, Freshwater Supply: States’ View of How Federal Agencies Could Help 

Them Meet the Challenges of Expected Shortages, GAO-03-514, July 2003. 

2

 Texas Rainwater Harvesting Evaluation Committee, Rainwater Harvesting Potential and Guidelines for Texas, 

Report to the 80th Legislature, Texas Water Development Board, Austin, TX, November 2006. 

3

 American Waterworks Association Research Foundation (AWWARF), Residential End Uses of Water, Denver, 

CO, AWWARF, 1999. 

4

 Pacific Institute, Waste Not, Want Not: The Potential for Urban Water Conservation in California, November 

2003. 

5

 See note 2. 

6

 Alan Traugott, Reclaimed Water and the Codes, Consulting-Specifying Engineer, April 1, 2007, available at 

http://www.csemag.com/article/CA6434236.html (accessed June 2008). 

7

 Susan R. Ecker, Rainwater Harvesting and the Plumbing Codes, Plumbing Engineer, March 2007, available at 

http://www.plumbingengineer.com/march_07/rainwater.php (accessed June 2008). 

8

 See note 7. 

9

 City of Portland Office of Planning & Development Review, Rainwater Harvesting – ICC – RES/34/#1 & 

UPC/6/#2: One & Two Family Dwelling Specialty Code: 2000 Edition; Plumbing Specialty Code: 2000 Edition, 

March 13, 2001. 

10 See note 7. 

11 See note 2. 

12 U.S. EPA, Drinking Water Costs & Federal Funding, EPA 816-F-04—038, Office of Water (4606), June 

2004. 

13 U.S. EPA, Sustainable Infrastructure for Water & Wastewater, January 25, 2008, available at 

http://www.epa.gov/waterinfrastructure/basicinformation.html (accessed June 2008). 

14 U.S. EPA, Water & Wastewater Pricing, December 18, 2006, available at 

http://www.epa.gov/waterinfrastructure/pricing/About.htm (accessed June 2008). 

15 U.S. Government Accountability Office, Water Infrastructure: Information on Financing, Capital Planning, 

and Privatization, GAO-02-764, August 2002. 

16 U.S. EPA, Water and Wastewater Pricing: An Informational Overview, EPA 832-F-03-027, Office of 

Wastewater Management, 2003. 

17 G. Tracy Mehan, Energy, Climate Change, and Sustainable Water Management, Environment Reporter – The 

Bureau of National Affairs, ISSN 0013-9211, Vol. 38, No. 48, December 7, 2007. 

18 Michael Nicklas, Rainwater, High Performance Buildings, Summer 2008. 

19 California Energy Commission, California Water – Energy Issues, Public Interest Energy Research Program, 

Presented at the Western Region Energy – Water Needs Assessment Workshop, Salt Lake City, Utah, January 10, 

2006. 

20 U.S. Department of Energy and U.S. EPA, Carbon Dioxide Emissions from the Generation of Electric Power 

in the United States, July 2000. 

21 King County Washington, King Street Center, Water Reclamation, available at 

http://www.metrokc.gov/dnrp/ksc_tour/features/features.htm (accessed June 2008). 

22 Natural Resources Defense Council, Case Study: The Solaire, Building Green from Principle to Practice, 

available at http://www.nrdc.org/buildinggreen (accessed June 2008). 

23 Don Talend, Model Citizens – High Rises in Manhattan’s Battery Park City are ahead of the Curve in 

Residential Water Treatment and Reuse, Onsite Water Treatment: The Journal for Decentralized Wastewater 

Treatment Solutions, September/October 2007, available at http://www.forester.net/ow_0709_model.html (accessed 

June 2008). 

24 Michael Zavoda, NYC High-Rise Reuse Proves Decentralized System Works, WaterWorld, February 2006. 

25 Center for the Built Environment, University of California, Berkeley, The Chesapeake Bay Foundation’s 

Philip Merrill Environmental Center, Mixed Mode Case Studies and Project Database, 2005, available at 

http://www.cbe.berkeley.edu/mixedmode/chesapeake.html (accessed June 2008). 

26 SmithGroup, CBE Livable Building Awards, Chesapeake Bay Foundation Philip Merrill Environmental 

Center. 

27 Center for the Built Environment, University of California, Berkeley, Award Winner 2007: Philip Merrill 

Environmental Center, Livable Buildings Award, available at 

http://www.cbe.berkeley.edu/liveablebuildings/2007merrill.htm (accessed June 2008). 
14

 

28 U.S. Department of Energy, The Philip Merrill Environmental Center, Chesapeake Bay Foundation Annapolis, 

Maryland, Office of Energy Efficiency and Renewable Energy, DOE/GO-102002-1533, April 2002. 

29 Jessica Boehland, Case Study: Alberici Corporate Headquarters, GreenSource. 

30 Alberici Enterprises, Alberici Corporation Builds Green, 2004, available at 

http://www.alberici.com/index.cfm/Press%20Room/Alberici%20Corporation%20Builds%20Green (accessed May 

2008). 

31 National Association of Industrial and Office Properties, Lazarus Building Serves as Example of Sustainable 

Development in Renovation of Community, September 19, 2007, available at 

http://www.naiop.org/newsroom.pressreleases/pr07greenaward.cfm (accessed June 2008). 

32 Matt Burns, “Green” Lazarus Building Gets National Accolade, Business First of Columbus, September 25, 

2007, available at http://columbus.bizjournals.com/columbus/stories/2007/09/24/daily10.html (accessed June 2008). 

33 Interface Engineering, Case Study: Stephen E. Epler Hall, Portland State University. 

34 Portland State Sustainability, Stephen Epler Residence Hall, available at 

http://www.pdx.eud/sustainability/cs_co_bg_epler_hall.html (accessed June 2008). 

35 Cathy Turner, A First Year Evaluation of the Energy and Water Conservation of Epler Hall: Direct and 

Societal Savings, Department of Environmental Science and Resources, Portland State University, March 16, 2005. 

36 Amanda Griscom, Who’s the Greenest of Them All – NRDC’s New Santa Monica Building May be the Most 

Eco-Friendly in the U.S., Grist, November 25, 2003, available at 

http://grist.org/news/powers/2003/11/25/of/index.html (accessed June 2008). 

37 Center for the Built Environment, University of California, Berkeley, The Natural Resources Defense Council 

– Robert Redford Building (NRDC Santa Monica Office), Mixed Mode Case Studies and Project Database, 2005, 

available at http://www.cbe.berkeley.edu/mixedmode/nrdc.html (accessed June 2008). 

38 Natural Resources Defense Council, Building Green – CaseStudy, NRDC’s Santa Monica Office, February 

2006.