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This page will provide you information on three topics:

  1. History of Greywater Use in California
  2. Current California Greywater Regulations
  3. Backyard Greywater Design Calculator

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General information

Greywater (also called graywater or grey water or gray water) is wastewater that has not come in contact with fecal material and is intended for reuse in irrigation. Greywater is a common method of water reuse with the benefit of reducing water consumption and preserving the water resource.
Greywater may not come in contact with fecal material due to contamination from pathogens. Because greywater will contain soaps, cleaning products, food particles and dyes, which may have nitrates, phosphates, bacteria, bleaches, solids (organic and not), and foam causing elements. Using water that contains these things may cause degradation to the surrounding environment, by changing the pH, overloading nutrients, and increases oxygen demand [1]. Greywater may contain, high levels of nutrients, and having a wetland treatment system can reduce contaminates through biological treatment and generate a healthier and more productive ecosystem.


California greywater defined

Greywater, defined by the California Health and Safety Code (Section 17922.12a) is “untreated wastewater that has not been contaminated by any toilet discharge, has not been affected by infectious, contaminated, or unhealthy bodily wastes, and does not present a threat from contamination by unhealthful processing, manufacturing, or operating wastes.” The Code continues to specify what systems can provide water to the system, the list includes: bathtubs, showers, bathroom washbasins, clothes washing machines, and laundry tubs. Any wastewater coming from kitchen sinks or dishwashers cannot be classified as greywater.


The California Water Code (Section 14877) defines a greywater system as “a system and devices, attached to the plumbing system for the sanitary distribution or use of greywater.” Cities or countries have the ability to add stricter standards to that of California’s and care must be taken learn about the local standards.

The United States has some of the most stringent requirements, with California having the first graywater code in the nation [2]. California’s code has up until 2009, been very restrictive and in most circumstances made it infeasible to install a permitted system. On August 4, 2009, California Plumbing Code adopted new regulations to help provide flexibility with water reuse systems.


History on greywater use in California

Summary Plumbing Code Ch. 16A

Chapter 16A, "Nonpotable Water Reuse Systems" was added as an emergency greywater regulation to the 2007 California Plumbing Code. The regulations were identifies as "emergency" to eliminate the 18 month waiting period that would otherwise have been required. Chapter 16A was approved by the California Building Standards Commission (CBSC) on July 30, 2009. The emergency regulations were filed with the Secretary of State on August 4, 2009, effective immediately upon filing. The Nonpotable Water Reuse Systems (Chapter 16A) is now part of Title 24, under Part 5 of the 2007 California Plumbing Code and was made a permanent part of the HCD Plumbing Code on January 27, 2010, with the unanimous approval of the CBSC.

The objectives of Chapter 16A are to conserve water by facilitating greywater use, reduce the number of non-compliant greywater systems, grovide guidance, and provide an alternative that would relieve stress on private sewage disposal systems[3]. Chapter 16A establishes minimum requirements for the installation of greywater systems. Part I of the code covers all persons and occupancies regulated by the Department of Housing and Community Development (HCD). The purpose of the code is to provide guidance to users while adding more flexibility to the process. This chapter of the code contains provisions which allows for the installation of limited types of greywater systems to be installed without a construction permit. However the code does not eliminate the need for persons considering the installation of a greywater system from contacting local authorities to ensure they are informed and in compliance with local requirements or prohibitions.

The Department of Water Resources (DWR) adopted Part II of Chapter 16A, which covers general permitting, labeling, signage, inspection and testing of the recycling water system. The main purpose of Part II of Chapter 16 is to insure the greywater system is identified so the public and persons work on or around the system are informed on the contants of the greywater pipes.

Title 24, Part 5, Chapter 16A "Nonpotable Water Reuse Systems" (Parts I and II)

California design criteria

The criteria set by Chapter 16A are given below, however it is important to check with local enforcement agencies for other local rules and regulations.

All greywater systems must meet the following requirements:

  • Not connected to potable water system
  • Design is based on location, discharge capacity, soil type and groundwater level
  • The area of discharge must be on the same plot as the source, unless lawfully exempt.
  • No construction until plan is approved (except for cloths washer or single fixture system)
  • Dual discharge must be available to switch between greywater and sewer
  • No dipper washing or contact with any fecal material
  • Greywater may not
- be used for spray irrigation
- pond up
- runoff
- discharge to storm sewer
- discharge to surface body of water
  • The discharge point must be covered by 2 in (51mm) material (mulch, rock, soil)
  • The greywater can not be used on root crops or edible parts of food crops


Greywater systems are separated into three categories:

  1. Single Fixture or Cloths Washer
    • no permit required
  2. Single System
    • exceeds washer or single fixture system
    • capacity is 250 gallons per day or less
    • Construction permit required
  3. Complex System
    • multi family or multi dwelling unit
    • capacity is greater than 250 gallons per day
    • Construction permit required


Construction Permits

  • Applies for Small or Complex Systems
  • Identify groundwater level and soil type for absorption qualities
- may use a 3 foot vertical test hole to show groundwater is lower than hole
  • All components must be water tight
  • Must be inspected by enforcement agency
  • Other local regulations and inspection requirements many apply (contact local enforcement agency)

Wetland design

A constructed wetland can be used in greywater applications for greywater treatment to help reduce pollutants before the water is released for irrigation.


How it Works
Greywater is discharged from the house to a either directly to into the greywater wetland or to a primary treatment system before going into the wetland. The primary treatment separates out some of the larger solids greses and oils. Primary treatment can be accomplished with filters, grease traps and settling tanks. In the greywater wetland the water undergo secondary treatment through filtration and other biological processes. The biological processes include the plants in the wetland, the bacteria that live on and around the vegetation and from the decomposition of the settled solids.

Primary treatment

Primary Treatment is the first treatment greywater receives. The objective of primary treatment is to remove grease and oils and larger solids from the greywater before the water is supplied to the wetland. Greses, oils and large solids can clog a wetlands and or kill beneficial bateria, resulting in a reduction in the wetlands treatment ability.
Primary Treatment is necessary if the greywater contains greases, fats and large particles, which is most likely the case when the kitchen sick is combined in the greywater system. However, California greywater systems cannot be attached to the kitchen sink, so primary treatment many not be needed for greywater systems in California.

For more examples and ideas go to greywater.com and theres a section on primary treatment in Subsurface flow constructed wetland for greywater.

Subsurface flow wetland

Location

When selecting a location for a greywater wetland, consider the following:

  • The wetland should be directly on the receiving end of an effluent flow
  • A downhill slope of about 0.5% - 1% [4] is recommended so water can flow by gravity through the wetland and then to the final discharge area.
  • The site should be easily accessible for monitoring and maintenance.
  • Do not construct the greywater treatment system in a pre-existing wetland.

Materials

list of required materials for construction of a subsurface flow wetland.

Sizing

Calculator goes here

Plumbing

Maintenance

Provide some general maintenance checks and timeline or continued operation of a subsurface flow wetland

Resources

  1. Yocum, Dayna, (2006), Design Manual: Greywater Biofiltration Constructed Wetland System, Bren School of Environmental Science and Management, University of California, Santa Barbara
  2. Greywater Action, 2010, “About Greywater Reuse”. <http://greywateraction.org/content/about-greywater-reuse>
  3. HDC, 2010, "Nonpotable Water Reuse Systems", California Plumbing Code, Title 24, Part 5, Chapter 16A, Part I, <http://www.hcd.ca.gov/codes/shl/Preface_ET_Emergency_Graywater.pdf>
  4. Crites, Ronald, and George Tchobanoglous, 1998, "Small and Decentralized Wastewater Management Systems." Water Resources and Environmental Engineering
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