Shades of greywater for your sustainable home | Digitized House

Guide to the Connected Home

Shades of greywater for your sustainable home

Shades of greywater for your sustainable home
Shades of greywater for your sustainable home

The full impact of the 2015-2016 El Niño weather phenomenon has yet to be determined, but as some areas of the United States are already receiving above-average rainfall or snow accumulation, ongoing concerns over long-term droughts may fall by the wayside. While an uptick in winter precipitation can ultimately lead to the recharge of critical watersheds and reservoirs, the premise of that expectation should not deter sustainability-minded homeowners from planning for optimal water conservation in their building or remodeling projects.

greywater water sustainability
Where is your greywater going? In this sustainable home, the water flowing into this vessel sink gets routed to landscape plantings after use through a branched drainage system.

Certainly, it is true the many-threaded issues related to residential water—including the topics of access, conservation, rainwater, reuse, wastewater and more—ebb and flow with the comings and goings of seasons and weather events. But it is also true there is much the homeowner can do to impact the issue in and around their dwelling, and that certainly applies to the recovery and reuse of greywater.

Taking the greywater plunge

The average home produces a significant amount of greywater—lightly used water emerging from bathroom sinks, showers, tubs, and washing machines—that can potentially be recovered and then diverted for reuse in irrigation of the garden and landscape, or in more ambitious applications, re-routed back into the home for use in toilet flushing. Particularly in the scenario of homeowners or would-be homeowners contemplating a sustainable, high-performance new home construction project, there is much that can be done in the planning and design phases to address the practice of greywater reuse.

greywater water sustainability
Shown here before the concrete foundation was poured for this home, the two main trunklines in a branched drainage system are visible as they exit the home. The wastewater trunkline on the left will be routed to a septic system, while the greywater trunkline on the right will be routed for reuse applications.

So, we would suggest the following question be added to your home-planning checklist: Has your architect or builder integrated greywater reuse thinking into the home plans? The most effective approach to greywater begins with the installation of a “greywater-ready” plumbing system layout during initial construction. In much the same way as solar-ready homes are pre-wired for the eventual installation of a rooftop solar photovoltaic system, greywater-ready homes are pre-plumbed during construction with a branched drainage system that can be easily tapped into following move-in to take advantage of greywater. These systems are assembled using the same type of white and green polyvinyl chloride (PVC) plastic pipe and fittings used in most homes.

Invest today, dividends tomorrow

When installed during the initial framing stage of construction, the branched drainage system will add minimal incremental cost, but can pay increasingly important future dividends in reducing overall water consumption—particularly in the event where water usage restrictions are enacted by your local municipality. Through the inclusion of two main PVC plumbing trunklines—one for reusable greywater and the other for wastewater or so-called blackwater coming from dishwashers, kitchen sinks, and toilets—the resulting water streams can be routed as desired following their exit points from the home. 

In the case of a greywater-ready home, where the actual water reuse applications may be planned and installed down the road, the greywater plumbing trunkline may initially be interconnected to the wastewater trunkline through a Y-shaped wye connector fitting, thereby enabling all water exiting the home to be routed directly to the sewage or septic system. Down the road, the wye connector can be bypassed permanently or on-demand with a valve system to enable the flow of the greywater for reuse. For example, a simple diverter valve setup and piping could be installed to route the greywater for immediate irrigation use around the landscape, or a more elaborate greywater processing system can be implemented.

greywater water sustainability
Most green home certification programs, including the U.S. Green Building Council’s LEED program, award points toward the desired certification for water efficiency features.

So it is all worthwhile? During drought conditions, where it may not be advisable or permissible to irrigate the garden, trees, and landscape, greywater recovery and reuse may supply sufficient water to sustain many of the respective plantings. And of course, greywater reuse should lead to savings on your monthly water bill, as you may be averting the use of hundreds of gallons of water each month. Furthermore, for homeowners pursuing a certification for their new construction project through a green home certification program, such as the U.S. Green Building Council’s (USGBC) Leadership in Energy & Environmental Design (LEED) program, points toward the desired certification level can be earned for water efficiency features, including greywater systems.

Of course, as always be sure to check local building codes to understand how and if greywater recovery and reuse can be integrated into your construction project, or added as a water-conserving enhancement to your existing home. 

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More info about this topic:
For an in-depth and holistic view of residential water issues, greywater, rainwater harvesting and more, see our article, “12 Days of Sustainable Reads: Day 9,” where we review the book The Water-Wise Home by Laura Allen.

An excellent resource for greywater, rainwater harvesting, and composting toilets:


Tom Kolnowski

Tom Kolnowski is the Chief Content Officer & Founder of Digitized House Media, LLC, the publisher of Digitized House | Guide to the Connected Home. When he isn’t writing about smart home technology, sustainability, and high-performance architecture, you’ll find him exploring faraway destinations with his family.