Water sustainability’s significance is growing due to increasing water scarcity and environmental concerns. Various methods toward water sustainability include focusing on best practices, building codes and certifications such as Leadership in Energy and Environmental Design (LEED).

This discussion delves into the role of low-flow fixtures, the importance of hot water system design and leak detection, and the potential benefits of greywater and rainwater systems in achieving water conservation. By understanding and implementing these strategies, we can address the immediate need for water conservation and contribute to energy efficiency and the well-being of ecosystems.

Low-Flow Fixtures: A Simple Yet Effective Solution

One of the fundamental approaches to water sustainability involves using low-flow fixtures. These fixtures limit water flow through plumbing systems, thereby reducing overall water consumption. Certifications such as LEED and Green Globes emphasize the importance of incorporating these fixtures in building design and construction by giving more points for certification due to the flow differential. 

For instance, the California Plumbing Code has taken a proactive stance by mandating low-flow fixtures and setting a maximum gallon per flush (gpf) at 1.28 gpf instead of the International Plumbing Code standard of 1.6 gpf.

While low-flow fixtures represent a step toward water conservation, their effectiveness is intertwined with the plumbing system design. Design considerations, such as the arrangement of plumbing systems and the integration of low-flow fixtures into the overall design, play a pivotal role in maximizing the impact of water-saving technologies.

Plumbing Design: Important to Conserve Water

Another factor in water conservation — and often an overlooked one — is the design of the hot water system in residential and commercial buildings. For homes, the typical hot water design does not include a recirculation loop. This is essential to maintaining hot water temperature. In some cases, the hot water piping can be installed below grade. In colder climates, the temperature drop in hot water piping can be significant when fixtures are not in use. 

Having no recirculation loop in residential applications leads users to run water at fixtures for extended periods to flush out stagnant, tepid water. This results in a significant amount of unnecessary water waste. 

Commercial buildings, on the other hand, typically incorporate recirculation loops in their hot water systems. This design choice minimizes the occurrence of water stagnation in pipes, reducing the need for flushing and, fortunately, conserving water. 

Attention to detail in hot water system design, including minimizing uncirculated hot water piping, is crucial for optimizing water usage efficiency in commercial applications. Codes have also started to recognize the importance of minimizing dead legs and that hot water routing and design play key roles in energy efficiency and water conservation. 

The International Energy Conservation Code is one of them. It requires the plumbing design to follow requirements restricting the length of the hot water dead-leg to a fixture that limits the volume of stagnant water in the system. By enforcing this restriction, the energy savings and efficiency come from the water heater needing to heat a smaller system volume to satisfy needs. By allowing a smaller system volume in the design, less water is used, leading to water conservation. 

Another plumbing design aspect that can be crucial for water conservation, especially in larger facilities, is leak detection technologies. If leaks within the facility go undiscovered, the effects can lead to substantial water waste and even bigger issues, such as damage to the building structure. When applicable, integrating leak detection systems into the plumbing design can establish a proactive approach to water conservation and even building maintenance because leaks within the piping can be caught early on.

Greywater Systems: Harnessing Clean Wastewater

An up-and-coming aid to water conservation is greywater usage. Greywater is defined as clean wastewater from sources such as lavatory sinks and showers; it presents a unique opportunity for water conservation. This type of water can be captured and repurposed for nonpotable uses, such as flushing toilets and irrigation. Greywater systems play a crucial role in minimizing reliance on the domestic cold water supply for items that do not necessarily require potable water.

Implementation of greywater systems involves careful planning and integration into building designs and collaboration early on to ensure its compatibility for the project, especially when it comes to cost. The capture and use of greywater can significantly reduce the demand for freshwater resources, contributing to overall water sustainability goals. 

Figure 1 illustrates a sample snapshot of a greywater piping system and its componentry, showcasing all the parts and pieces of this water-saving strategy.

Rainwater Harvesting: Effect on Landscape Architecture

Rainwater harvesting stands as a transformative practice with profound implications for sustainable water management and landscape architecture. This approach aids in reducing potable water use for irrigation by capturing and using roof rainwater runoff in lieu of potable water. Much like greywater systems, rainwater harvesting represents a strategic endeavor to repurpose a valuable resource that would otherwise be underused. 

Various methods are available to provide water for irrigation, including planting low-water and regionally adaptive plant material, placing plants by similar water needs, implementing drip irrigation with flow sensor technology, and using rainwater for irrigation before it is directed back to the local stormwater system. 

Rainwater harvesting involves installing systems that collect rainwater as it flows off rooftops. This harvested rainwater is then stored in tanks or cisterns, ready to be used for landscape purposes. Figure 2 depicts the rainwater harvesting cisterns at Austin Community College San Gabriel Campus Center. The cisterns are beautifully designed as part of the architectural language, becoming a focal feature of the outdoor student seating area while providing awareness of sustainable practices. 

If storing rainwater is not an option, rainwater can still passively aid in landscape irrigation. Rainwater from building roofs and site hardscapes can be diverted to the landscape by using bioswales, site grading design and other green infrastructure methods. This helps reduce potable water use and filtrate runoff before entering the stormwater system. 

Integrating rainwater harvesting systems requires early coordination with the design team and the project client to evaluate design implementation, cost and ongoing maintenance requirements to create different solutions that best fit the client, architectural aesthetic and regional area.

The Tolleson Civic Center in Tolleson, Ariz., exemplifies the successful integration of water sustainability and aesthetics through interdisciplinary collaboration. In this instance, the collaboration between plumbing, architectural, landscape and structural disciplines played a pivotal role in incorporating water-conscious design principles while enhancing the facility’s visual appeal. 

The coordination efforts focused on managing storm drainage from the roof, necessitating a joint approach to channel a portion of the building’s runoff into a dedicated drain column.

Within this collaborative framework, the rainwater captured in the drain column is guided into a roof drain rain basin meticulously designed by landscape architects. This basin not only serves a functional purpose but also contributes to the overall aesthetic harmony of the civic center. To ensure the quality of the captured rainwater, a drain at the basin’s bottom filters out impurities before the water is directed to a retention tank, a crucial element in the water management strategy. 

Civil engineers played a key role in this stage, contributing their expertise to optimize the flow and storage of rainwater. Figure 3 illustrates the column to the right of the lobby entrance and how well it blended in with the other structural columns for the building. The synergy between diverse disciplines and their thoughtful integration into the design process resulted in a well-conceived facility that goes beyond mere functionality.

Being wasteful is something people don’t like to live with, so why can’t we live better by starting to apply ways to be sustainable with our water supply and usage? Methods and systems such as providing low-flow fixtures, hot water system design, leak detection, and greywater and rainwater systems each play a vital role in mitigating water wastage and promoting responsible water use. Collaborative efforts between designers, clients and policymakers are essential to ensure the effective implementation of these strategies.

As we strive to save water, we contribute to the current population’s well-being and pave the way for a more sustainable future. By integrating water-saving technologies into our built environment and adopting best practices, we can create a positive impact on energy efficiency, ecosystem health and overall water management. Water sustainability is not a trend but a necessity for a better world. 

Lhymwell Manalo is a plumbing engineer at SmithGroup’s Phoenix office. He is a member of the American Society of Plumbing Engineers and has seven years of experience designing plumbing systems for various building types. 

Cristal Castro is a landscape designer at SmithGroup’s Phoenix office. She has seven years of experience designing in the desert and enjoys collaborating to find creative design solutions for regional issues.