Step by Step Laundry to Landscape Greywater Systems

Below is an overview of the steps and considerations involved with installing laundry-to-landscape systems— the most accessible source of greywater. This overview summarizes information described in the Monterey County Business Council: A Homeowner’s Guide to Conserving Water (November 2012) and from the City of Santa Cruz Greywater Informational Handout (March 2014).

Laundry-to-landscape systems do not require a building permit if the requirements outlined in Chapter 16 of the 2013 California Plumbing Code are followed.

Note: Greywater can NOT be stored for later use; graywater becomes septic and can be harmful to animals and humans. Greywater can NOT be applied at the surface; it must percolate through a subsurface mulch basin, and NO runoff can occur.

Step 1: Estimate your Greywater Production

  1. How many loads of laundry are done in a typical week?
  2. How many gallons of water are used per load?
    • Older top-loading machines use about 40 gallons/load
    • Front-loading machines use about 20 gallons/load (Some EnergyStar machines are top loading. Front-loading EnergyStar machines use about 15 gallons/load. Today’s current standard load is about 25 gallons/load.)
  1. Are there future changes to consider, such as installing a new washing machine, increases or decreases in the number of occupants, or changes in landscape?  Here's a simple formula:  Loads per Week x Gallons per Load = Weekly Greywater Produced.

Step 2: Decide What Plants to Irrigate

  1. Plants with larger root zones do better with graywater-irrigation.
  2. The plants stay happier and healthier with consistent laundry water patterns. 
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apples

Step 3: Estimate Plant Irrigation Requirements

Does Your Greywater Production = Your Plant Irrigation Requirements?
Pick the right amount of plants based on your greywater 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 determined through online research or through contacting a local nursery.

Step 4: Plan the Path of Travel

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. Importantly, these systems should not be installed at properties with high water tables.

Topography:

  • Irrigate flat areas or the closest downhill area to the washer.
  • In a flat yard, distribution should be within 50 feet of the washing machine.
  • If the site slopes downward to distribution points, there is no rule on distance—however,  it is recommended to use tubing that curves to slow gray-water flow on downhill slopes.
  • Try to maintain a downward slope whenever possible.

Number of distribution points:

  • Top-loading machines can irrigate up to 12 mulch basins, and
  • Front-loading machines can irrigate up to eight mulch basins.

Piping to landscape must be:

  • 1.5 feet from buildings and property lines.
  • 100 feet from wells, creeks and storm drains.
  • Piped around obstacles—go under, around, remove, or cut a strip from hardscapes (e.g. patios or walkways). 
Path of travel

Step 5: Installation

Please refer to online literature about how to correctly install the:

  • Three-way valve, which allows the user to direct greywater into either the existing sewer line or the new greywater-irrigation pipelines;
  • Air vent/air admittance valve, which prevents formation of a vacuum within the new pipeline; and
  • Proper 1” poly tubing and mulch-basin distribution points, which carry the greywater from the laundry to the root zones of plants within the landscape. 

Step 6: Product Choices

Avoid using products that can harm soils and plants. These products include but are not limited to:

  • Salts or sodium compounds;
  • Boron, borax, or borate;
  • Peroxygen, petroleum distillate or alkyl benzene;
  • Chlorine bleach (hydrogen peroxide bleach is okay);
  • Water softeners that use sodium chloride (potassium chloride is okay); and antibacterials, which alter the biology of natural occurring bacteria in the ground and groundwater

Step 7: Safety and Maintenance

Each system must have its own Homeowner’s Maintenance and Operations Manual, detailing the working parts, layout of system, and maintenance requirements. The 3-way valve must have a label directly above it, detailing the direction of flow. This manual must stay with the operational greywater system in the event that the homeowner(s) or tenant(s) cease to live at the property. Furthermore, the following steps must be adhered to:

  • Do not eat plants or vegetables that have come in direct contact with greywater (e.g. root vegetables).
  • Water used to clean soiled material (e.g. diapers, oily rags, etc.) must be diverted to the sewer using the 3-way valve.
  • Greywater must be diverted to the sewer during the rainy season, typically October 1 through April 1, to eliminate ponding or runoff.
  • Do not store it—greywater must be diverted into the landscape or sewer immediately.