Liquid Gold: Harnessing Rainwater for a Sustainable Future  

Photo courtesy of Saltz-Michelson Architects

An integrated rainwater capture system enhances the water and energy efficiency of The Nancy J. Cotterman Center in Ft. Lauderdale, Florida. 

Rainwater harvesting has entered a new age. Once comprised of standalone tanks, pumps, filters, and pipes, rainwater systems are now integrated solutions that benefit both building occupants and the wider community. This shift reflects a growing recognition of rainwater not as waste but as a valuable resource to be captured and used. “In North America, over the last 15 years, we have witnessed the birth of a brand-new industry sector: rainwater harvesting,” says G. Edward Van Giesen III, MLA, and National Sales Manager for Watts RainCycle. “While roof drains, tanks, cisterns, pumps, and filters are nothing new, integrating them into a cohesive system is.”

This systems-based approach marks a paradigm shift in understanding the role that rainwater plays within the built environment. Modern rainwater harvesting systems must adhere to evolving codes, standards, and health regulations to ensure both safety and long-term viability. “Previously, Architects and Engineers viewed rainwater collection as a set of disparate parts and pieces,” Van Giesen explains. “Now, more and more designers understand that a rainwater system is greater than the sum of its parts.” With growing pressure to reduce potable water use and manage stormwater runoff, rainwater harvesting offers a practical, scalable solution.

WATER CONSERVATION: A GROWING IMPERATIVE IN BUILDING DESIGN

Freshwater is often seen as abundant and inexhaustible in many parts of North America, especially areas with regular rainfall. However, there are limits to the amount of freshwater available for potable use. Both underground aquifers and surface water sources are like bank accounts; if withdrawals exceed replenishment, there will be a net loss.

Historically regarded as a nuisance to be redirected away from structures, rainwater is now being re-evaluated as a valuable natural asset—an increasingly essential component of sustainable design.

Photo courtesy of Watts Water Technologies, Inc.

Large underground fiberglass cistern for storing rainwater at Forest Arms Apartments in Detroit, Michigan.

Rainwater harvesting presents architects and engineers with a multi-benefit strategy that conserves potable water, mitigates urban flooding, and enhances site-level environmental performance. Applicable across project types and geographic regions, these systems contribute to both local resilience and global sustainability targets.

Rethinking Water: Conservation and Infrastructure

Despite perceptions of abundance, freshwater supplies in North America are under mounting pressure. Factors such as aging infrastructure, population growth, and shifting climate patterns are converging to make water scarcity a concern even in rain-rich regions.

Many municipalities still depend on combined sewer systems (CSOs), which combine stormwater with sanitary sewage. As a result of the never-ending expansion of impervious surfaces, these combined systems of pipes, drains, catch basins, and treatment plants are periodically overwhelmed during heavy rain events. When this occurs, untreated wastewater can overflow directly into receiving waters, which are frequently the same bodies of water that provide drinking water for municipalities.

Integrating rainwater capture at the building scale offers architects a proactive way to reduce the load on municipal systems, limit nonpoint source pollution, and enhance watershed performance. Moreover, the paradox of frequent flooding in areas facing water shortages highlights the urgency of systems that can retain and repurpose excess rain. Rainwater harvesting directly addresses this gap, transforming a liability into a long-term asset.

Water Security: A Global and Local Challenge

Ensuring reliable access to freshwater is a growing concern worldwide and a critical issue for architects to consider in sustainable design. A United Nations 2022 report found that 2.2 billion people still lacked access to safely managed drinking water services. This global crisis demands immediate action, including improved distribution infrastructure and the expanded use of alternative, site-sourced water solutions such as rainwater harvesting.

Decentralized rainwater collection can ease pressure on overstressed municipal systems by supplementing potable supplies and buffering against the impacts of climate volatility. Capturing and storing rainwater not only conserves treated water for essential uses but also helps prevent urban flooding by diverting runoff from storm drains and sewers. Even simple collection systems offer high-impact benefits when scaled across multiple buildings and communities.

Water-Energy Nexus: Strategic Insights from Sandia National Laboratories

Sandia National Laboratories is at the forefront of research into the interdependence of water and energy systems, emphasizing their significance for national security and sustainability. Their work highlights how water availability directly impacts energy production, including hydroelectric power, thermoelectric plant cooling, and fuel processing. Conversely, energy is essential for water treatment and distribution, creating a cyclical dependency between the two resources.

A notable contribution from Sandia is the development of decision-support tools designed to assist policymakers and stakeholders in evaluating strategies under varying water availability scenarios. These tools aim to enhance the resilience and sustainability of energy-water systems.

In the realm of hydraulic fracturing (fracking), the Natural Resources Defense Council (NRDC) reports that fracked wells can consume between 1.5 and 9.7 million gallons of water per well, depending on various factors. In California, concerns have been raised about the substantial volumes of freshwater used in oil extraction processes, especially in drought-prone regions like the Central Valley. NRDC

For architects and designers, understanding the water-energy nexus is crucial. Incorporating decentralized water systems, such as rainwater harvesting, into building designs can reduce reliance on municipal water supplies and enhance resilience against water scarcity. These systems contribute to sustainability goals and offer practical solutions to the challenges posed by the intertwined nature of water and energy resources.

The Regulatory Landscape of Rainwater Capture

Rainwater harvesting systems offer an effective, sustainable way to capture natural precipitation for non-potable uses such as irrigation, landscaping, flushing toilets, and potable end uses. However, despite increasing interest in this water conservation practice, inconsistent regulations and unclear terminology continue to pose challenges.

By examining the key terminology and legal considerations, designers can better navigate these obstacles and create effective, code-compliant systems.

Regulatory Confusion: Terminology and Standards

Despite the growing recognition of rainwater harvesting as a sustainable practice, there is still confusion surrounding its regulatory framework. One of the primary barriers to adoption is the inconsistent classification of rainwater. In many jurisdictions, rainwater is incorrectly classified as graywater, leading to the imposition of more stringent and unnecessary treatment standards. This confusion not only adds cost and complexity to the system but also discourages architects and planners from integrating rainwater harvesting into their designs.

The key issue lies in understanding the distinction between different types of water. While graywater and blackwater require intensive treatment to ensure safety and prevent contamination, rainwater is generally much cleaner, especially when collected from clean, impervious surfaces like rooftops. Rainwater only becomes graywater if it is mixed with graywater, making it crucial for design professionals to differentiate between these water sources in their documentation. Misclassification based on terminology can result in the application of inappropriate standards, causing delays and escalating system costs.

Understanding these distinctions is essential for compliance and effective system design. Rainwater can be safely used for non-potable purposes with appropriate treatment, such as irrigation, cooling towers, or toilet flushing. This is in stark contrast to graywater, which requires more sophisticated filtration and disinfection before it can be reused. Designers need to be precise and clear in their system documentation to ensure the appropriate source water classification and avoid unnecessary regulatory hurdles.

Legal Considerations and Code Compliance

The legal landscape for rainwater harvesting in the United States is diverse and often complex. Regulations vary significantly from state to state and even within local municipalities, creating a patchwork of legal requirements that can complicate the design, installation, and permitting of rainwater harvesting systems. Each jurisdiction may have its own set of regulations regarding system size, storage capacity, and intended use (e.g., irrigation, non-potable uses, or potable use).

Water Rights and Regulations

A key distinction in rainwater harvesting regulations stems from the different approaches to water rights across the country. In eastern states, water rights are typically governed by riparian rights, which allow landowners to use water from nearby bodies (e.g., rivers, lakes) as long as they own the land adjacent to the water source. Western states, on the other hand, adhere to prior appropriation laws, which treat water as a property right. Under prior appropriation, water use often requires a permit and may be subject to limitations. These regional variations can complicate the installation of rainwater harvesting systems, as some states may impose restrictions on how much rainwater can be captured and may require additional permits for its use.

Building Codes and Standards

Over the past fifteen years, most states have had the opportunity to adopt language from either the Uniform Plumbing Code (UPC) or the International Plumbing Code (IPC). These model codes offer language that allows states to adopt rainwater provisions as they see fit. For example, the California Plumbing Code is based on the UPC but is not a replica; the state may adopt certain sections and omit others. The same applies to other states that use the IPC as a foundation.

ARCSA

“ARCSA International is the first place professionals should go for information regarding rainwater system design. Since 1994, the organization has led the way by providing training and certification to interested parties, and developing standards and codes at the state, national, and international levels. More than ever, ARCSA continues to be relevant and necessary for those seeking to incorporate the practice of Rainwater Harvesting into their building design.” Heather Kinkade, executive director of ARCSA International.,

ARCSA International, formerly known as the American Rainwater Catchment Systems Association (ARCSA), is a professional organization that is an excellent source for detailed information on the subject. ARCSA International’s mission is to promote sustainable rainwater harvesting practices to help solve potable, non-potable, stormwater, and energy challenges throughout the world. ARCSA International also provides resources, research, education, professional certifications, and training.

Designing for Demand: Integrating Conservation with Rainwater Harvesting

Successful rainwater harvesting systems begin with a strong foundation in water conservation. Architects play a key role by specifying low-flow plumbing fixtures, water-efficient appliances, and energy-smart equipment. When conservation principles are embedded early in the design process, the overall demand for water is reduced, which allows for more appropriately sized harvesting systems.

Planning for Outdoor Use

Outdoor water demand varies widely based on regional climate, landscape choices, and occupant behavior. Designers should prioritize xeriscaping and native or drought-tolerant plant species suited to local conditions. It is also important to keep runoff sources separate: water collected from paved surfaces should be stored separately from roof runoff, especially if it’s intended for indoor use.

Residential Constraints and Benefits

While residential systems aren’t typically able to supply all of the water to irrigate large, turf-heavy landscapes, due to their relatively small roof footprint, they can still reduce reliance on municipal water supplies. Even small-scale systems make a meaningful contribution to sustainable water management, benefiting both homeowners and the community.

Photo courtesy of Watts Water Technologies, Inc.

Water closet using rainwater for flushing at the Nancy J. Cotterman Center in Fort Lauderdale, Florida.

Indoors, rainwater can serve multiple non-potable functions such as toilet flushing, clothes washing, and cooling tower makeup. With appropriate treatment, it may also be used for potable purposes, including drinking, bathing, and showering. As water quality expert Dr. Peter Coombes noted, “Properly collected and stored rainwater meets most public health standards for potable use.”

Note that using rainwater for potable purposes requires more advanced treatment processes.  Special permits are often required in public buildings, if allowed at all. For example, the State of Virginia has recently ratified a potable rainwater code, offering a regulatory model for such use.

Across North America, hundreds of thousands of rainwater (residential and commercial) systems are already in operation, underscoring rainwater harvesting’s potential to meet water conservation goals and enhance building resilience.

Rainwater Systems: Calculating Resources

Once the demand side is addressed, it’s crucial to design a system that meets these needs efficiently. A rainwater collection system should be viewed holistically, considering collection, storage, filtration, and treatment together as an integrated whole.

Core Elements Overview:

Photo courtesy of Watts Water Technologies, Inc.

The inside of an underground fiberglass tank.

The inclusion of all of the primary elements of a rainwater system is essential for its performance. While specifics will be covered later in this article, these elements are:

1. Inlet Pre-Filtration: Removes debris before water enters the storage tank.
2. Storage: Properly sized to match rainfall supply and demand.
3. Filtration and Treatment: Tailored to the system’s intended use, from drip irrigation to potable water.

Various other components should be incorporated to optimize system performance and water quality. Detailed discussions of these components can be found in the later section dedicated to rainwater system parts.

Sizing the System

Sizing a rainwater harvesting system requires considering several factors, including local climate, available catchment area, and estimated demand in volume. Effective systems aim to balance collected water with demand, minimizing overflow during wet seasons, and storing enough water for dry periods.

Local climate data, such as historical precipitation patterns, is key to calculating storage capacity. Resources are available through ARCSA International to help design professionals estimate potential collection volumes. Precipitation data is available online through the National Oceanic and Atmospheric Administration.

Condensate Recovery: An Untapped Water Source

HVAC systems generate condensate—water that can be captured and reused for non-potable purposes such as irrigation and toilet flushing. Though biologically active, HVAC condensate typically contains low levels of dissolved solids. When properly treated, this water source is a great supplement to a rainwater collection system.

Design Considerations:

• Yield Factors: Recovery potential depends on climate, HVAC system type, and building size.
• Water Quality: Depending on the application and local codes, condensate will require some treatment and disinfection before use.

System Components: Designing for Efficient and Clean Rainwater Harvesting

Designing a rainwater harvesting (RWH) system that is both efficient and capable of producing high-quality water requires a thoughtful approach to its individual components. Each part—from roof to tap—must work in concert to minimize contaminants, ensure structural integrity, and optimize system performance. As architects and engineers look to integrate water conservation strategies into sustainable building design, understanding each system component’s purpose and design considerations is critical to achieving the desired outcomes of water quality, quantity, and long-term functionality.

Roof Catchment Surface

The roof serves as the primary rainwater collection surface. Its materials, slope, and maintenance directly affect both the quantity and quality of water harvested. Rainwater can be collected from virtually any roof surface, but the material type may affect the output water quality.

Collection Surface: The first element of the rainwater collection system is the collection surface. The type, age, size, and composition of the collection surface impact the quality of the water flowing over its surface. The longer the water stays in contact with the surface, the more time it has to react with it. Metal, clay, asphalt, wood, tar, slate, vinyl, or rubber—the roof surface’s type and texture will affect the water runoff quality. A smooth surface will allow more water collection and mitigate absorption and evaporation. Membrane-type roofs are commonly used in commercial roofs and perform exceedingly well in shedding water from their surfaces. Powder-coated metal roofs have a smooth surface and resist corrosion. The most common surface type for residences is asphalt shingles. There has been much discussion on the suitability of asphalt shingles for rainwater harvesting systems; however, for most non-potable systems, they pose little risk to the user.

Care must be taken for systems intended to serve potable applications to ensure that the water flowing from these surfaces does not contain chemical contaminants such as heavy metals. It’s easy to determine if heavy metals are present by performing simple water tests first to understand if these contaminants are present and if the treatment system can remove them from the water.

Green roofs are becoming increasingly common in commercial buildings. They have many benefits to both the building owner and the community at large. They act as sponges and can slowly release the rainwater over time, and allow it to evaporate. However, they produce contaminants, which are usually absent from clean roof surfaces. The resulting runoff will usually be dark brown. In addition, they contain particulates from the growing vegetation and naturally decaying plant material. While generally unsuitable for most indoor applications, such as toilet flushing and cooling tower makeup, they are usually not problematic in outdoor irrigation end uses.

Roof Drains, Gutters, and Downspouts

Internal roof drains, external gutters, downspouts, and storm risers direct the flow of rainwater from the catchment area to storage. These components channel rainwater from the roof to the storage system. Properly sized and positioned gutters ensure reliable water conveyance during heavy rainfall.

Design Considerations:

• Sizing: Roof drains, gutters, and downspout dimensions must be designed according to state and local codes regarding sizing.
• Material Selection: Non-corrosive, durable materials such as aluminum, PVC, or stainless steel are best where codes permit. Materials should be compatible with collected water quality goals.
• Debris Management: In residential applications, screens, leaf guards, or mesh filters can reduce organic debris but may require maintenance. Gutter slopes (1/16” to 1/8” per foot) should encourage rapid drainage and minimize stagnation. The same applies in commercial applications, but the filters are larger and typically more sophisticated.
• Accessibility: Easy access to gutters and downspouts for inspection and cleaning improves long-term system performance and user satisfaction in residential applications.

First-Flush Diverters

First-flush diversion improves water quality by diverting the initial runoff from the roof, which typically contains higher levels of dust, bird droppings, and other pollutants. Even on high-rise buildings with little chance of finding leaf debris from trees, atmospheric deposition will build up on the roof surface. These pollutants include auto emissions, tire and brake dust, soot from fires, and even fine soil particles.

Design Considerations:

• Volume Calculation: The volume to be diverted depends on the catchment area and expected pollutant load. A common rule of thumb is to divert the first 1/8 inch of rainfall.
• Automatic or Manual Options: Gravity-fed diverters are simple but require diligent, frequent maintenance. More sophisticated systems can automate the diversion process using electronically activated valves and controls.

Drainage and Maintenance: Diverters must drain fully between events to avoid mosquito breeding and microbial growth. Drain valves or soakaway pits can support healthy system operation

Pre-Filtration Units

Before rainwater enters the storage tank, it should be pre-filtered to remove suspended solids, debris, and coarse particulate matter. Effective pre-filtration protects downstream components and reduces long-term maintenance.

All pre-filters are variations on a theme. They are screens designed to keep accumulated debris from the roof from entering and fouling the water in the tank. The screens are usually made of plastic or perforated stainless steel with a micron size between 350 and 1,000 microns. Note that mesh size and micron size are not the same. The pre-filter is installed between the collection surface and the inlet to the storage tank.

Cleaning Schedule: Filters must be regularly inspected and cleaned to prevent clogging and overflow. Design for easy access and minimal disruption during maintenance

These devices mitigate the intrusion of unwanted contaminants in the system. The absence of one will require more frequent cleaning of the storage tank and any filters in the system.

Aeration: Aeration with fine bubbles can greatly improve water quality conditions in the storage tank. Over time, depending on the amount of organic deposition in a given tank, anaerobic zones may form and produce strong-smelling odors as the water is used.

Traditional sediment filtration will not eliminate these odorous gases, nor will UV treatment. Aeration is a simple and effective way of addressing this issue. It provides a level of “insurance” against these smells.

In addition to providing oxygen to support the beneficial aerobic bacteria in the tank, this strategy also allows for any noxious anaerobic gases that may form in the tank to be expelled via the tank vent. The air pumps may be electric, wind-driven, or other non-electric means where electricity is unavailable. They do not need to run 24/7; the timing should be adjusted based on site-specific criteria, typically once a day for several hours during non-peak demands.

Storage Tanks

Photo courtesy of Saltz-Michelson Architects

Pumping, filtering, and treating unit mounted on a skid at the Nancy J. Cotterman Center.

Photo courtesy of Watts Water Technologies, Inc.

Below-grade fiberglass cistern prior to the installation at the Nancy J. Cotterman Center in Ft. Lauderdale, Florida.

Below-Grade Fiberglass Cistern: The heart of the rainwater harvesting system is the storage tank. It must be properly sized, located, and protected to ensure safe, clean, and reliable water storage.

Design Considerations:

• Material Types:

• • Polyethylene/Polypropylene (Plastic): Lightweight, corrosion-resistant, and affordable; UV-stabilized versions offer longevity outdoors.
  • Concrete: Durable and offers thermal stability; suitable for underground installations, but may require sealing to prevent leaching.
  • Fiberglass and Steel: Strong and long-lasting; typically used for commercial systems.
  • Galvanized sheet metal tanks: These are often chosen for urban or suburban locations. Some designers like the rural look of these corrugated round tanks. They are available in sizes from 600 to more than 600,000 gallons and are simple to build. The larger tanks might be used for schools or high-rise buildings. Zinc-coated tanks are corrosion resistant, and the interior can be fitted with a PVC liner or coated with waterproof spray-in liners.
• Tank Size and Siting: Storage volume depends on catchment area, location, and the volumetric demand. Tanks should be sited out of direct sunlight and adhere to applicable building codes.
• Light and Contaminant Protection: Tanks must be opaque to mitigate algae growth. Vents should be screened to prevent insect or animal entry.
• Overflows and Access: Overflow pipes should direct overflows from foundations. Access ports should be large enough for inspection and maintenance and able to be secured from unauthorized entry.
• Multiple Tank Configurations: Modular or daisy-chained tanks allow scalability and ease of installation in constrained sites.

Unless the rainwater system consists of a rain barrel connected to a hose bib by gravity, it will need some post-storage filtering for no reason other than to keep pipes from clogging with accumulated debris. Where rainwater is used for indoor purposes (potable or non-potable) and outdoor spray irrigation, adequate filtering and treating (disinfecting) is essential. Most jurisdictions require disinfection even for non-potable applications.

Rainwater systems typically use a multi-stage, step-down filtration strategy to remove suspended material in the water. After filtering, rainwater can be treated (disinfected) using various techniques. UV disinfection is the most common method in the rainwater industry, but ozone and chlorine treatment may be used. UV disinfection is a simple process, requiring only annual bulb replacement and utilizing no chemicals.

Though technically not a disinfection method, ultrafiltration (generally between 0.01 and .5 micron) can filter the vast majority of waterborne microorganisms without any additional treatment.

Pumping and Pressurization Systems

With rare exceptions, rainwater harvesting systems will incorporate some form of pumping to create enough flow and pressure to meet the building’s demand. Pumping systems need to be sized to deliver the flow and pressure required by the building. These may be as simple as stand-alone pumps with on-off switches or large sophisticated pump skids capable of delivering pressurized water throughout the building. A water treatment skid is a self-contained, portable system mounted on a skid or pallet.

Distribution and End Use

Once filtered, treated, and pressurized, rainwater is delivered to its point of use. Design must ensure hygienic delivery, avoid cross-contamination, and match flow rates and pressures to intended applications.

Design Considerations:

• Dedicated Plumbing: The piping in the building delivering non-potable water must be separate from the potable lines. Clear labeling and proper backflow prevention are required by codes and are good practices.
• Flow Monitoring and Control: Flow meters can support conservation goals and help detect leaks or misuse.
• Backup Water Supply Integration: Makeup or bypass supplies from a municipal source or well water are necessary if an uninterrupted water supply is desired. In commercial applications and most residential ones, the makeup or bypass operation should be automated.

System Monitoring and Maintenance

RWH systems are not static. They should be closely monitored and maintained over the life of the system.

Design Considerations:

• Monitoring Tools: Water level indicators, turbidity sensors, and real-time monitoring systems provide valuable insights. Some systems integrate with smart home platforms and commercial building management systems.
• Inspection Ports and Access: Tanks, filters, and treatment equipment should be readily accessible for inspection. Maintenance schedules should be clearly outlined in building operations and maintenance manuals.
• User Training: Building occupants or facility managers should be educated on system function and maintenance responsibilities.
• Documentation and Compliance: Keep records of inspections, water quality testing, and component servicing to meet local health department or green building certification requirements.

An Integrated Approach to System Design

A successful rainwater harvesting system is more than the sum of its parts—it is a well-orchestrated network of components, each performing a specialized function to ensure clean, efficient, and reliable water collection and delivery. Architects and engineers must consider how each element interacts with the others, adapting to site conditions, building use, and local climate. By prioritizing quality materials, redundancy, and ease of maintenance, design professionals can deliver systems that not only conserve water but also enhance public health and environmental resilience.

Return on Investment in Rainwater Harvesting Systems

When architects and building owners consider rainwater harvesting, one of the first questions is often financial: What is the return on investment? While ROI is a familiar metric in sustainable design, calculating it for rainwater systems requires a broader lens.

In favorable conditions, when a building has high water demand and ample roof surface area for collection, rainwater harvesting can offset a significant amount of municipal water usage. This reduction in utility dependence results in clear cost savings, especially in larger commercial or institutional buildings. However, the actual payback period depends on numerous factors, including capital costs, local water rates, and how well the system is matched to the building’s actual water use.

Oversizing or undersizing a system can negatively impact ROI. A rarely full cistern represents unnecessary capital expense, while one that’s too small may fail to supply enough water to make a difference. The more a designer understands the building’s water use patterns, the more effectively they can tailor the system for efficiency and economy.

Simplicity is often the best path to value. Systems that are straightforward in design tend to have lower installation and maintenance costs and perform more reliably over time. For residential projects, ROI may not always be financial; the return could be greater water independence or the satisfaction of environmental responsibility. In contrast, commercial systems—particularly in areas where water is costly or heavily regulated—may offer a clearer economic payback.

It’s also important to recognize that conventional ROI calculations often exclude externalized or societal costs. Municipal water rates rarely reflect the full expense of water sourcing, treatment, delivery, and infrastructure upkeep. If these hidden costs were internalized, decentralized systems like rainwater harvesting would become even more economically attractive. They reduce the burden on municipal infrastructure, lower energy use, and contribute to long-term community resilience.

Can Rainwater Harvesting Increase Property Value?

While specific studies on rainwater harvesting’s impact on properties are limited, general data suggests that sustainable features can boost property values:

• A study by Maiden Capital indicates that sustainable residential real estate investments, including water-saving measures, can lead to a property value increase of 10 to 14 percent.
• The Urban Land Institute’s report on green infrastructure highlights that comprehensive green infrastructure, which may include rainwater harvesting, can significantly enhance property values over time.

Example Calculation: Assuming an apartment building is valued at $1 million:

10 percent increase: $100,000

14 percent increase: $140,000

These figures suggest that investing in a rainwater harvesting system could substantially increase property value, potentially offsetting the initial installation costs.

Considerations

• Local Incentives: Some regions offer tax credits or rebates for sustainable building features, which can further enhance the return on investment.
• Market Demand: In areas where tenants prioritize sustainability, a rainwater harvesting system can make the property more attractive, potentially leading to higher occupancy rates and rents.
• Operational Savings: Beyond property value, rainwater harvesting can reduce water bills, contributing to overall savings.

While the exact increase in property value varies, integrating a rainwater harvesting system into an apartment building can offer significant financial and environmental benefits.

Recap and Conclusion: Rainwater Harvesting as a Design Imperative

As detailed throughout this course, rainwater harvesting is a practical and increasingly necessary solution to modern water challenges. It addresses both immediate project needs, such as reducing potable water use, and long-term goals like infrastructure resilience and climate adaptation. From commercial facilities, multifamily buildings, and single-family homes, rainwater systems offer flexible solutions that scale with context.

Key Benefits in Practice

• Resource Efficiency: Rainwater can be reused for landscape irrigation, toilet flushing, and other non-potable needs, easing demand on potable supply.
• Environmental Impact: Reduces runoff, recharges aquifers, and supports local watershed health.
• Economic Value: Cuts utility bills and infrastructure costs while potentially qualifying for green building credits.
• Energy Link: Less water transported and treated means lower energy consumption and carbon emissions.
• Design Integration: With thoughtful planning, rainwater systems can be seamlessly incorporated into architectural form and site layout.

Legal and Regulatory Context

The regulatory landscape remains fragmented, making early planning and code review essential. Differentiating rainwater from graywater—and ensuring proper separation from potable systems—remains key for compliance and safety.

Architects as Sustainability Leaders

Design professionals are positioned to champion rainwater harvesting as part of a holistic sustainability strategy. By integrating systems early, architects can influence both the form and performance of a building, ensuring rainwater is managed and used. This elevates water from a liability to an asset, creating design narratives that reflect environmental responsibility.

Conclusion

Rainwater harvesting is no longer optional in a climate-stressed world—it’s a strategic design tool that supports sustainability, resilience, and occupant wellbeing. As building codes evolve and performance expectations grow, architects and engineers must lead the way in transforming rain from runoff into resource. When captured with purpose, rainwater supports high-performance buildings and reflects a larger ethic of stewardship—one that turns every drop into an opportunity.

Case Study: Forest Arms Apartments, Detroit, Michigan

 

Photo courtesy of Watts Water Technologies, Inc.

Detroit developer Scott Lowell.

 

While Detroit’s post-bankruptcy recovery included stormwater management reforms that charge building owners for runoff, Lowell found it challenging to qualify for stormwater fee reductions despite installing a comprehensive system. “We didn’t get the discount, but we definitely got the savings,” he said in a February 2025 interview. “I haven’t drunk the green Kool-Aid; I just don’t like paying the man.” Even with an upfront investment that was far from inexpensive, the project saw a payback period quicker than the anticipated seven years, thanks to reduced water consumption and rising municipal rates. Lowell emphasized that while such systems are not “plug and play,” they require minimal monthly maintenance—about two hours—but offer long-term financial and marketing advantages. “Tenants like the idea of these green features,” he added. “There’s a marketing aspect to it.”

Photo courtesy of Watts Water Technologies, Inc.

The storage tank is ready to be placed at Forest Arms Apartments.

 

Forest Arms Apartments stands as a leading example of how sustainability can align with economic common sense, particularly in legacy urban buildings. Lowell, a Detroit native, is now applying lessons from Forest Arms to two new residential projects in the same neighborhood—both of which will include rainwater reclamation systems and geothermal heating and cooling. “We found our niche,” he said, noting that even in the absence of sweeping incentives, savvy developers can take advantage of federal, state, and historic tax credits to make water-saving infrastructure financially viable. As Lowell begins work on converting a crumbling 1892 Victorian house into eight new apartments, his track record suggests that green retrofits aren’t just good for the environment—they’re good business.