Water

Water efficiency retrofits: 

  • Laundry-to-landscape greywater irrigation system
  • Rain gardens
  • Drought tolerant and native planting
  • Water-efficient dishwasher and clothes washer replacement
  • Water-efficient fixture replacement (toilets, kitchen and bath faucets, showerheads)
Block-scale management of rainwater systems. (work completed by Christine Scott Thomson, Senior Associate at Page/, as part of Phase I* of the Oakland EcoBlock (*project phase completed while at another firm, SOM))

Laundry-to-Landscape Greywater Irrigation System

A laundry-to-landscape greywater system captures greywater from the discharge hose of your washing machine, enabling you to reuse the water without altering the existing plumbing in your home. In this system, the hose leaving the washing machine is attached to a valve that allows for easy switching between the greywater system and the sewer. It is important to be able to switch to the sewer anytime you don’t want to send the water outside, for example if you’re using bleach, which could harm plants, or if the soil is saturated during the rainy season. The greywater is distributed through a 1-inch irrigation line with outlets directing water to specific plants (see figure below). This system is low-cost, easy to install, and very flexible if you need to make future changes to your home or landscaping.

Laundry-to-landscape overview. Source: Clean Water Components and SF Water.

Benefits of Greywater

Reusing greywater is an important component of sustainable water practices. There are many benefits of using greywater instead of potable drinking water for irrigation.

Reusing greywater can:

  • Decrease potable water use by 16 to 40 percent, depending on the site (Cohen 2009).
  • Decrease water and wastewater utility bills.
  • Reduce the energy (approximately 2 watt-hours per gallon of water) and chemicals needed to treat wastewater.

Another benefit of using greywater is that it connects us to our water supply, helping us understand where our water comes from and where it goes. Becoming conscious of our water supply encourages healthier product choices and engagement with our landscape. By reusing household greywater, we preserve water resources for other living things. In concert with water-wise landscaping, rainwater harvesting, and conservation, using greywater as a resource helps reduce dependency on imported water and protects watersheds.

Plant friendly products should be used with your greywater system. In general, products should be biodegradable and non-toxic. In addition, they should be free of salt (sodium) and boron (borax), two common ingredients that are non-toxic to people but are harmful to plants and/or the soil. Chlorine bleach is also harmful to plants and should be diverted with any other harmful products to the sewer or septic by switching the 3-way valve. See this article for recommendations on specific brands.

Residents may also consider using filtering devices that collect microfibers that come off of clothing during wash cycles to keep microfibers from entering the greywater system. Devices range from fine mesh laundry bags to small coiled balls that can be placed in the washing machine.

Rain Gardens

A rain garden is a garden of native shrubs, perennials, and flowers planted in a small depression, which is generally formed on a natural slope. It is designed to temporarily hold and soak in rainwater runoff that flows from roofs, driveways, patios or lawns. Rain gardens are effective in removing up to 90% of nutrients and chemicals and up to 80% of sediments from the rainwater runoff. Compared to a conventional lawn, rain gardens allow for 30% more water to soak into the ground.

In the design of a rain garden, typically six to twelve inches of soil is removed and altered with tillage, compost and sand to increase water infiltration. The type of alteration to the soil depends on the current soil type, so it is a good idea to obtain a soil test.

Rain gardens are generally constructed on the downside of a slope on your property and collect rainwater runoff from the lawn, roof and/or the driveway. Once water collects in the rain garden, infiltration may take up to 48 hours after a major rainfall. Rain gardens also incorporate native vegetation; therefore, no fertilizer is needed and after the first year, maintenance is usually minimal.

Drought Tolerant and Native Planting

Designing for rainwater capture through native, drought-tolerant planting and efficient irrigation systems is an effective way to lower outdoor water use. Residents may consider replacing private property (lawns and yards)—which require substantial amounts of water and fertilizer—with “California-friendly” plants minimizes maintenance and irrigation, restores soil health, attracts local pollinators and wildlife, and enhances the aesthetic beauty of the natural landscape. 

Residents should consider the following planting design fundamentals to cultivate beautiful and sustainable native landscapes:

  • Direct water from downspouts and impermeable surfaces, such as concrete walkways or driveways, to swales, the landscape, or other permeable areas to keep water on-site and benefit your plants.
  • Plant in the fall or during the rainy season to take advantage of the rainfall for establishing your plants and minimizing your irrigation needs.
  • Group plants with similar water, sun, and soil needs. If you plan to use your irrigation system, be sure that plants with the same water needs are in the same irrigation zones.
  • Space plants based on their mature size for growth. This will help prevent an “overgrown” look, and minimize water and maintenance needs.
  • Build healthy soils to support healthy plants. Avoid using synthetic fertilizers and chemicals. Allow leaf litter to stay in place to promote nutrient cycling.

Sources and Resources:

Groundwater Foundation
The Groundwater Foundation is a non-profit organization that provides education and community-based action programs involving individuals, communities, and public and private entities in groundwater conservation and protection. The Foundation website covers current issues impacting groundwater and provides resources for groundwater resource management.

California Native Plant Society
The California Native Plant Society (CNPS) is an environmental non-profit organization that seeks to conserve California native plants and their natural habitats and increase understanding, appreciation, and horticultural use of native plants. The CNPS website provides resources for selecting native, drought-tolerant plants, gardening and plant installation, and long-term maintenance.

San Francisco Graywater Design Manual for Outdoor Irrigation
A technical resource for homeowners and professionals who want to install greywater systems for outdoor irrigation in San Francisco, though much of it applies to other cities as well. This manual provides a detailed step-by-step process for designing and installing laundry-to-landscape systems, as well as the basic steps for designing and installing branched drain and pumped systems. The manual provides an overview of the benefits of greywater systems, when and where to install these different systems, permitting requirements (SF-specific), what products to use, and operation and maintenance requirements.

Greywater Action
A website with detailed information about greywater reuse, among other household water systems. Information is available in Spanish and Chinese.

Video: “How to Install a Graywater Irrigation System” (This Old House)

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