Graywater Rebate

• Adhere to state and local regulations, including Chapter 15 of the California Plumbing Code. 
   
• Your property should have the following features to be most suitable for this rebate:
   
  • The clothes washer is near an exterior wall or above a crawlspace,
     
  • The landscape should be about the same elevation or downhill from the clothes washer,
     
  • The first plant irrigated with graywater should be within about 50-feet from the clothes washer (or farther if it's downhill),
     
  • You plan to irrigate trees, shrubs, vines, or groupings of smaller plants with graywater, and
     
  • The point graywater leaves its piping should be at least 1.5-feet from the property line and from building foundations.
     
• No filters, no tanks, and no pumps (except for the pump in the clothes washer itself) are allowed or needed for Graywater Laundry to Landscape Systems.

• All graywater must be gravity-fed and distributed from the clothes washer to a pre-approved landscape area that is large enough to absorb the graywater. 
   
• Mulch basins are required. A mulch basin is a trench dug around the outer edge of a plant's drip line and back-filled with mulch. A plant's "drip line" is an imaginary line drawn from the outside branches of a plant down to the soil (see inset image). Additional information is in About Graywater. 
   
• The landscape area with mulch basins must be sufficiently sized to prevent runoff and pooling of graywater. 
  • A specific required square footage will be provided before or upon receiving your Notice to Proceed. This square footage is based on the amount of graywater expected to be produced and the landscape’s soil type. 
  • The graywater system may have one or more valved zones. Mulch basins within each zone must meet or exceed the required square footage provided. 
     
• The site where graywater is used must be in an area where seasonally high groundwater is at least five feet below ground surface. This will be verified by the District using available information. 
   
• Graywater must: 
  • Not be stored, must not runoff into streets and waterways, and must not pond nor pool on the soil surface. 
  • Not be used to irrigate root crops or edible parts of food crops that touch the soil. 
  • Be contained on the site where it is generated. 
  • Be distributed subsurface or released to an area covered by a minimum of two inches of soil, bark, rock, mulch, or appropriate permeable cover.
  • Have an unobstructed exit route into the landscape (for example, if every valve is accidentally closed, the graywater is still able to reach the landscaping).
     
• Avoid shallow utilities (water, gas, electric) or septic systems by calling the Underground Service Alert at (800) 227-2600 or 811 before you dig.

• The graywater system and parts thereof must be on the same lot (parcel) as the building or structure that discharges the graywater. 
   
• Graywater must be distributed at least: 
  • 18 inches from the property line (Note: this minimum distance requirement shall be increased if the adjacent property is downhill from the graywater distribution point(s).); 
  • 2 feet from buildings; 
  • 50 feet from any septic tank or leach field; and 
  • 100 feet from wells, waterways, or other water sources. 
     
• Graywater piping/tubing and the diverter (3-way) full-port ball valve shall be the same diameter as or larger than the clothes washer drain hose. Typically, 1-inch diameter. 
   
• The end of the main-line tubing shall be left fully open (allow a continuous unobstructed graywater route from the clothes washer to the landscape; never use a valve or plug on the distribution point furthest away from the clothes washer.). 
   
• The graywater system shall: 
  • Not include a potable water connection, filters, nor a pump. (Note: The pump in a clothes washer is not considered part of the graywater system.) 
  • Not connect to overhead (spray) irrigation nor to a conventional irrigation system. 
  • Be designed to prevent clogging of any emitters. 
  • Be designed and installed to prevent contact with humans and pets. 
  • Be labeled on every 5 feet of exposed graywater piping with, “Caution: Nonpotable graywater. Do not drink.” Labels may be provided upon request. 
  • Include a diverter (3-way) full-port ball valve to allow the user to direct the flow of graywater between the graywater system and the sanitary sewer/septic system. 
  • Include an auto vent (or an in-line vent or an air-admittance valve). 
     
• The diverter valve and auto vent assembly: 
  • Must be installed at least 6 inches above the flood rim (typically the top) of the clothes washer. 
  • Must be easily accessible and labeled. Labeling shall indicate which direction to turn the diverter valve’s handle to send graywater to either the landscape or the sanitary sewer/septic system, respectively. Example labeling may be provided upon request. 
  • Shall be used to direct to the sanitary sewer/septic system all wastewater derived from activities that could create health issues. These activities include, but are not limited to: 
    • Washing diapers or similarly soiled garments, 
    • Washing greasy or oily rags, 
    • Cleaning car parts, 
    • Disposal of waste solutions from photo labs, and 
    • Other activities that contain hazardous chemicals. 
       
• Any perforations in the building created during installation are properly sealed or patched. 
   
• The finished system must include an operating and maintenance manual. The manual is to remain with the building throughout the life of the system. Upon change of ownership or occupancy, the new owner or occupant shall be notified that the structure contains a graywater system and provided the manual. A template manual may be provided upon request.
   
• To facilitate future maintenance, the operating and maintenance manual shall include a diagram depicting the final locations of graywater piping, distribution points, and mulch basins with respect to the property line and landscape. 

The amount of graywater your clothes washer will produce depends on two factors:

1. Your laundry habits, and
    
2. The age and type of your clothes washer. A newer, high-efficiency front-loader clothes washer may use less than 15 gallons per cycle compared to an older, conventional top-loader, which may use 45 gallons per cycle. That’s three-times the amount of graywater! 

Estimate how much graywater you may produce in a week to get a sense of how much of your landscape can be irrigated with the graywater.

Weekly Graywater Produced = Loads per Week x Gallons per Load

Does your graywater production equal how much water your plants need? Pick the right amount of plants to irrigate based on your estimated graywater output.

Irrigation requirements depend on whether the plants being irrigated are water-intensive (e.g., fruit trees), drought-tolerant, or somewhere in the vast middle. Plants usually have an estimated water demand factor that can be found through online research or by contacting a local nursery. If you apply for the rebate, we'll help you estimate this.

On average, an older top-loading clothes washer produces enough water for an 800 square-foot area of trees, shrubs, and vines. For a rough estimate: 

• A front-loading clothes washer can provide water for 1 tree for every load per week and up to 8 outlets overall. 

• A top-loading clothes washer can provide water for 2-3 trees for every load per week and up to 12 outlets overall.

To help calculate the amount of graywater needed to irrigate your plants, see Table 1 in this PDF from the University of California Division of Agriculture and Natural Resources.

Graywater is a fantastic method to prioritize the plants you want to be more resilient to drought and a hotter climate. If you have an existing irrigation system, identify a zone/valve that can be shut off and replaced with graywater.

Trees, shrubs, and vines are appropriate choices for this type of graywater system. Design a simple, effective system by knowing:

• Which plants you want to send graywater to
   
• About how much water they may need
   
• About how much graywater you make in your home

The specific plants you decide to irrigate with graywater will depend on how frequently you do laundry, the type of clothes washer you have, the climate near your home, and the types of plants you’re irrigating. If you apply for the rebate, we’ll help.

Laundry-to-landscape systems have limitations that affect the graywater’s path of travel through a landscape, including topography (slope), number of distribution points (i.e., mulch basins), and piping placement.

If you need to get past a cement patio, walkway or another impervious surface, consider installing a permeable hardscape (State of California Water Board). Or, go under or cut a strip from the hardscape. Review the distance rules provided in the Graywater Rebate Requirements for additional details.

From your clothes washer, the graywater piping will be in a shallow trench (deep enough to avoid trip hazards) connecting each mulch basin. A single mulch basin may have more than one mulch shield (graywater outlet) and the mulch basin can be any shape (circles or trenches are most common). The bottom of the mulch basin should be as flat as possible.

For every one foot run of pipe you lay down, you may go down ¼ inch in grade. So, for a 20-foot run, the line will eventually be 5 inches below the grade from where you started in a completely flat yard. The graywater piping may tee-off to ½-inch lines in most mulch basins as long as there’s a continuous route between the clothes washer and the last mulch basin where the piping stays the same diameter as the clothes washer’s washer line throughout.

Laundry-to-Landscape Systems divert your laundry rinse water directly to the landscape. The only pump is within the clothes washer itself. The only filter is the soil and the mulch basins you install. This allows for a simpler, cost-effective system that’s easier to maintain and use over the long-term.

An example parts list is provided, including how many you may need is provided on the Rebate Requirements page. Additional, fewer, or slightly different components may work better for your project. Continue reading for the most essential equipment.

Essential components include: 

• Diverter (3-way) valve
   
• Auto vent
   
• Transition to the landscape side of the system
   
• Mulch basin (graywater outlets)

Essential Components

Full-Port Diverter (3-way) Ball Valves

• This should have the same diameter as the clothes washer's drain hose, typically 1-inch diameter.)
   
• 3-way valves allow you to direct graywater into either the existing sewer line or the new graywater-irrigation pipes. If you want to do a load of laundry with bleach, use the 3-way valve to send it to the sewer.

Auto Vent (or comparable equipment such as Air-Admittance Valves or In-Line Vents)

• This prevents a vacuum forming by breaking any siphon-effects in the graywater piping.
   
• PE (polyethylene), HDPE (High-Density Polyethylene or poly-tubing), quick-connect or locking PVC, purple reclaimed water pipe and/or PVC (Schedule 40).
   
• Most projects require fewer than 100-feet of tubing/PVC to carry the graywater from the clothes washer to the root zones of plants within the landscape. It should be the same diameter as your clothes washer’s washer line (typically 1”-diameter, but newer clothes washers have ¾”-diameter). 

Other equipment: 

• the correct PVC glue to attach the fitting to the pipe (the glue depends on the type of pipe material).
   
• A grade level and tape measure. 
   
• As needed, ½-inch black poly tubing to tee to all but the final mulch basin (to prevent clogs, there must be a continuous route between the clothes washer and last mulch basin that stays the same diameter as your clothes washer’s washer line). 

Where to find equipment?

• Online Vendors (See "8. Suppliers and Other Organizations" towards the bottom of the page; Greywater Action)
   
• Physical Stores and Other Online Vendors (Central Coast Greywater Alliance)
   
• Valley Water’s Landscape Resources includes lists of local irrigation supply stores, nurseries, and landscape professionals that may be able to provide additional assistance.

What about tools? Check out the PG&E Tool Lending Library. Hardware stores and some libraries also offer tool-rental or tool-lending services.

The most effective graywater “filter” is biologically-active soil covered in mulch! Mulch basins help you avoid removing large particles like hair or lint and help add organic matter back into the soil--organic matter in the soil results in healthier soil and makes it easier for your plants to absorb nutrients. 

What’s a mulch basin?

Mulch basins catch large particles in mulch, help transform the mulch into compost over time, and help the graywater soak down into the soil to irrigate plant roots. A mulch basin is a trench dug around the outer edge of a plant's drip line and back-filled with mulch. A plant's "drip line" is an imaginary line drawn from the outside branches of a plant down to the soil (see inset image). 

• Mulch basins can be any shape. They are typically as wide as a shovel. They should be as flat as possible to help graywater flow evenly.

• The graywater pipe is protected in a "mulch shield", separated from the surface above and more mulch below. This setup allows graywater to spread widely and deeply into your soil while preventing runoff or ponding of graywater. 

• Maintenance typically includes checking the ends of the graywater pipe for obstructions to remove and replacing the mulch as it composts over time (once a year in general). Coarser mulch will last much longer than finer mulch and will be better at filtering out any large debris from the graywater.

How do you size a mulch basin?

The amount of area you need to contain mulch basins is determined by how much graywater you produce and your soil type to prevent pooling, ponding, or runoff of graywater. Healthier soils will reduce the size of mulch basins while making it easier for your landscape to benefit even more from graywater. When you apply for the rebate, Valley Water will provide you the total square footage you’ll need based on how much laundry you do and the type of soil in your landscape.

How do you install a mulch basin?

Avoid shallow utilities (water, gas, electric) or septic systems by calling the Underground Service Alert at (800) 227-2600 or 811 before you dig.

• To install a mulch basin, locate the outer edge of the canopy on each plant -- its drip line. If it’s a younger plant, imagine where its outer edge may be in a year or two. Too far out and the plant won’t benefit as much from the graywater; too close in and you may damage the plant’s roots when digging. 
   
• Immediately outside of the drip line, begin creating a 6-18 inch wide and 6-12 inch-deep trench with a shovel. The mulch basin shall be deep enough so that the graywater pipe is 2-inches below the soil surface within a mulch shield, and the mulch shield rests on a 2-inch cushion of mulch within the mulch basin. The top of the mulch shield will be visible from the basin. 
   
• A valve box can be used as mulch shields. These can be purchased at a hardware store, a home improvement store, or from a landscape supply store. Some garden centers and nurseries sell them as well. Larger, round valve boxes provide more space to place and adjust the piping as you finalize your system.

To avoid mistakes, dry-fit your piping and test how the graywater flows. It’ll be much easier to adjust your piping and mulch basins, and tighten loose connections when everything is still unglued and exposed.

Whether you’re starting a new landscape project or maintaining your existing landscape, this information will help you quickly and easily find landscape professionals in your area. Receive advice and resources on home horticulture, pest management, and sustainable landscape practices from Santa Clara County's UC Master Gardeners.

Landscape professionals with rebate experience

The lists below are intended to help you find companies familiar with Valley Water’s rebate programs with experience in landscape design, construction, and maintenance. This information is not intended to be an endorsement of any one company. 

• List of companies that have experience working the Landscape Rebate Program projects and/or Graywater Installation, including the Graywater Rebate Program or Direct Installation projects.

Landscape professionals: If you wish to be added to or removed from this list or have general questions, contact Ashley Shannon at (408) 630-2951. Be prepared to verify that you have had three or more clients participate in the Landscape Rebate Program to be eligible to be added to the list.

Landscape professionals with sustainability background

This section provides a variety of landscape professional resources. They may not have experience with Valley Water's rebate programs, but do have experience in sustainable landscape practices or efficient irrigation techniques.

• Find a Qualified Water Efficient Landscaper in your area. A certification program to educate landscape professionals and their customers on effective landscape design, management and irrigation practices, QWEL landscapers are trained in water-wise landscape practices including:
  • plant selection,
  • irrigation system design, and 
  • water Management
     
• Find locally-trained landscapers to help reduced water use and improve irrigation efficiency with the WaterSense Program.
   
• Find a Green Gardener trained in sustainable landscape maintenance practices.
   
• The California Landscape Contractors Association offers a list of certified landscape contractors also.
   
• Greywater Action and Central Coast Greywater Alliance provide lists of experienced graywater contractors also.