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Graywater Rebate

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COVID-19 Program Notice

Through Valley Water's Graywater Rebate, receive up to $400 to install a Graywater Laundry-to-Landscape System to make your landscape more resilient with a local, sustainable water supply. 

This type of graywater system sends rinse water from your clothes washer directly to your landscape without filters, tanks, or pumps. It's a cost-effective, sustainable option to upgrade how you irrigate your landscape. 

Who qualifies

Homeowners in Santa Clara County with a qualifying property. If you can answer "yes" or "possibly" to the following statements, then your property likely qualifies:

  1. The clothes washer is accessible, near an exterior wall or above a crawl space.
  2. The landscape's first graywater outlet is 50 feet or less from the clothes washer, or a bit further distance downhill.
  3. The landscape is the same elevation or downhill from the clothes washer.
  4. The plants you want to prioritize with graywater irrigation are decorative trees, fruit trees, shrubs, groups of smaller plants or establishing drought-tolerant plants.
  5. The graywater system can be at least 1.5 feet from the property line and building foundations.

Projects must also adhere to state and local regulations, including Chapter 15 of the California Plumbing Code

Learn more about all kinds of graywater systems.

Rebate amount

The rebate amount ranges from $200 to $400 for qualifying residents. 

Residential customers in these service areas may be eligible for the higher $400 rebate amount:  

  • City of Cupertino (note: sites in unincorporated areas in Cupertino are not eligible for the higher rebate amount)
  • City of Morgan Hill water customers
  • City of Palo Alto Utilities customers
  • San José Municipal Water Systems. To confirm you're in this service area, enter your address or check your water bill.

Funds are first come, first served, while funding is available.

Steps to apply

Step 1: Before you apply, prepare and plan

Step 2: Apply for the rebate

You can apply for a rebate online or by mail. The application must be approved before you begin any work. 

Step 3: Design and installation

Review the following tips for planning the design and installation of your laundry-to-landscape system. If you apply for a rebate, our staff can help with this step.

Estimate how much graywater your clothes washer produces

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

  1. Your laundry habits.
  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

Estimate how much graywater your plants need

Does your graywater production equal your plant irrigation requirements? 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) or drought-tolerant. 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.

Decide which plants to irrigate with graywater

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.

Plan the graywater route

Laundry-to-landscape systems have limitations that affect the graywater’s path of travel through a landscape, including topography, 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). 

For every four 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.

Get the graywater equipment

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?

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

Placing the graywater mulch basins

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). 

  • 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 mulch basin you’ll need 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.

Step 4: Post-inspection

When you receive your Notice to Proceed, you should also receive an example owner’s manual and information about what to expect during the post-inspection. To schedule your post-inspection, call the Water Conservation Hotline at 408-630-2554 or email [email protected].

Step 5: Rebate payout and system maintenance

Upon a successful post-inspection, your rebate payment will be mailed to you within 4 to 6 weeks.

See About Graywater for additional information about choosing detergents and maintaining your successfully completed Graywater Laundry-to-Landscape System.

Questions

Call the Water Conservation Hotline at 408-630-2554 or email [email protected].