The increasing development of worldwide green building projects, especially those related to the Leadership in Engineering and Environmental Design (LEED) standard, provide the contextual basis for the implementation of water conservation strategies. As access to clean water continues to be a source of concern in many areas of the world (including the U.S.), water efficiency strategies in green building practices are becoming paramount to new and existing construction efforts. Given the scope of terms associated with water efficiency in green building, there are numerous terms that describe key elements in the design and implementation of water conservation strategies.

One of the most important elements of understanding water efficiency is the diversification of water terms in green building practices. In particular, the LEED standard identifies four key types: Potable Water, Graywater, Blackwater, and Process Water; all of which provide different utilities in green building water efficiency processes.

Below are several definitions related to each type of water in the LEED standard in order to provide greater understanding of utility in the green building process.

Potable Water: Using the Environmental Protection Agency’s definition as a framework, the LEED standard expresses potable water as meeting quality standards for human consumption by local and/or state authorities. In order to protect a clean, reliable source of water, the LEED standard, in particular, discourages the use of potable water in non-potable applications such as landscaping or indoor plumbing needs.

Graywater: To protect the unnecessary use of potable water, green building practices under LEED emphasize the use of graywater for a variety of non-potable applications such as landscaping and indoor plumbing. Defined as untreated wastewater that has not come into contact with water closet waste, graywater emanates from bathtubs, showers, and bathroom wash basins. The high applicability of graywater on a LEED project in meeting landscaping requirements or limiting potable water use for water closets and urinals is the main element of its importance to green building practices.

Blackwater: On the other hand, blackwater is the antithesis to both potable and graywater, as it is not suitable for any human contact (either direct or indirect) given the contents that constitute its definition: wastewater from water closets and urinals. However, it is important to note that in some state and local codes, wastewater from showers, kitchen sinks, and bathtubs are considered blackwater as well, thereby expanding its definition and illuminating the need to identify its presence on a green building project. Given the nature of blackwater, the LEED standard discourages any use of blackwater to replace potable water use and is generally considered limited in utility until treated, which according to LEED should be completed on site to tertiary standards.

Process Water: The use of process water, especially in the LEED rating systems, is not regulated for water efficiency processes, given its utility in cooling towers, chillers, and boilers. The most important element of process water, however, is the limited use of potable water to be used as process water, as the LEED standard ultimately discourages the use of potable water in non-potable applications.

The differences in water definitions in green building practices are an important element for determining water efficiency capabilities. As one of the main tenants of the green building practices, especially in LEED, understanding the components of water forms is important in implementing water efficiency practices. However, while the aforementioned list of water types is an important starting point to understand water efficiency in LEED projects, there are a variety of applicable water-related terms not discussed here that also play a major role in the development of green building water practices.

If you would like to learn more about the role of water efficiency in green building practices, especially LEED, Everblue offers a LEED Green Associate course that can prepare you to gain a greater understanding of green building elements. For more information, please visit Everblue’s LEED Green Associate course, call us at (800) 460-2575, or email us at [email protected].