Guidelines for Graywater Filters to Protect Drainfields & Drywells
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• Graywater filters & how to use them to protect the drywell or drainfield

This document discusses the design and use of graywater filter systems to protect drywells or the septic drainfield or absorption system from clogging. Graywater filters may be placed at the inlet to a drywell or graywater disposal system. Washing machine filters are often installed at the clothes washer outlet hose. We include a list of product sources for these various types of drywell or gray water filters.

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First, a simple "sock" type lint filter (photo at left) can be installed at the clothes washing machine.

This graywater filter method is easy and effective to install for laundry systems that empty from the washing machine into a laundry sink.

We used to use an old pair of panty hose - which works but less effectively than a real lint filter. (Photo courtesy of thenaturalhome.com - see Product Source List below)

A second graywater filter system uses a filter installed inside a graywater pumping chamber or located between the building drain and the inlet to the drywell or to whatever other graywater dispersal and absorption system is in use.

This system is used for either effluent filtering or gray water filtering when there is not room to install a filter directly in the graywater pumping chamber or in the septic tank. (Photo courtesy of thenaturalhome.com - see Product Source List below).

Filter Chamber Installation: Whether the effluent or graywater filter is installed at the outlet end of a septic tank, the inlet to a drywell, or separately as an interim filtering chamber (as shown here), a riser may need to be installed to permit ready access to inspect and change or clean the filter.

Some states (such as Montana) require that access risers to be least 21" in diameter, and to have an access cover within 6" of grade and even if your state does not, that standard makes sense.

To protect the absorption system, the chamber which holds the filter must (in some states) have a shut off mechanism (such as a ball float switch) so that effluent will not pass through when the filter cartridge has been removed for cleaning or replacement.

When a septic tank riser is installed (to give access to a septic tank cover or to a filter chamber), it replaces the lid (which was on the septic tank at the outlet end, for example) and a new lid is placed at grade to provide convenient access to the equipment. (Courtesy National Small Flows Clearinghouse, edited and added comments by DJF.)

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SEPTIC SYSTEM DESIGN ALTERNATIVES
  Wastewater Treatment Levels
  Wastewater Dispersal Methods
  Master List of Septic System Types
  AEROBIC SEPTIC SYSTEMS
  ALTERNATING BED SEPTIC SYSTEMS
  CESSPOOLS
  DRYWELLS
  SEPTIC EFFLUENT DISINFECTION SYSTEMS
  EVAPORATION-TRANSPIRATION SEPTIC SYSTEMS
  FIXED-FILM PROCESS SEPTIC SYSTEMS
  MEDIA FILTER SEPTIC SYSTEMS
  SEPTIC & GREYWATER FILTERS
    Signs of a Clogged Septic Tank Filter
    Graywater Filters
    Septic Filter Maintenance
    Septic Filter / Graywater Filter Sources
  MOUND SEPTIC SYSTEMS
  RAISED BED SEPTIC SYSTEMS
  SAND BED SEPTIC SYSTEMS
  SEWAGE TREATMENT SYSTEMS
  TOILET ALTERNATIVES
  VEGETATED SUBMERGED SEPTIC BEDS
  WETLAND SEPTIC SYSTEMS
  ALTERNATIVE SEPTIC DESIGNERS
  ALTERNATIVE SEPTIC PRODUCTS

• MEDIA FILTER SEPTIC SYSTEMS
• SEPTIC SYSTEM DESIGN BASICS
• Don't Flush these things into a septic system: a list of what's ok and what's not ok to put into septic tanks and building drains
• Septic Tank Pumping Frequency Guide for Septic Tanks: When, How, What to Watch For when pumping or cleaning septic tanks
• SEPTIC SYSTEM DESIGN ALTERNATIVESNew York State Wastewater Treatment Standards - Individual Household Systems, Appendix 75-A (1990), Public Health Law 201(1)(1).
• New York State Alternative Septic System Design Regulations, Wastewater Treatment Standards - Individual Household Systems, Appendix 75-A, of Public Health Law 201(1)(1) 1990.

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