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Guide to Using Septic Filters and Graywater Filters to Protect Drainfields InspectAPedia®  -     What are septic effluent filters or septic tank filters? How using a septic filter can extend the life of the septic drainfield Signs of a clogged septic filter or clogged drywell filter Graywater filters for extending drywell life Septic filter or gray water filter product sources

This document discusses the design and use of various types of septic effluent filter systems and graywater filter systems to protect the septic drainfield or absorption system from clogging. Septic filters are such a significant improvement in septic system operation and longevity that some jurisdictions (such as Arizona) require them on new septic installations. Also see SEPTIC MEDIA FILTERS for difficult site septic designs, and see septic filter products listed at Septic Filter / Graywater Filter Sources.

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The Basics of Using Septic Filters to Extend Septic Drainfield Life

While there are several versions of septic and other types of wastewater filters, the most basic septic effluent filter is a simple tee and filter installed at the septic tank outlet. The installation can be handled by a septic contractor or a skilled homeowner, and can cost less than $100. U.S.

These simple septic filters, such as greywater filters, washing machine filters, and filters at the effluent outlet of a conventional septic tank are all designed to protect the septic effluent absorption field or leach field. Septic filters are placed either in the septic tank at the outlet tee or in a separate chamber outside of and close to the septic tank. 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 septic filters.

In contrast with septic effluent and graywater filters, media filter septic systems use a conventional septic tank followed by any of several methods to further filter and treat septic effluent before it is discharged to the soil, soil surface, or waterway. Media filter systems are discussed at Using Septic Media Filters as Components of Alternative Septic Systems for Difficult Sites.

Septic Effluent Filters Protect the Leach Field from Clogging

To add protection for the septic absorption system, add a septic effluent or gray water filter at the septic tank outlet tee. The sketch at page top (US EPA) shows a large basket filter installed at a septic tank outlet. The photo at left shows a simple filter which is installed inside the outlet tee of a septic tank. If there is no room in the tank to install such a filter, a small chamber and filter can be installed outside of the septic tank but upstream from the drainfield. Although most grease or large solids entering the septic tank are intended to be retained there where they are reduced to floating scum at the top of the tank or settled sludge at the tank bottom. However septic tank effluent also contains suspended solids, smaller particles of debris which, as they pass out to the soil absorption system, or drainfield, speed the clogging of the absorption system and thus shorten its life. By trapping more of the suspended solids in septic effluent we pass clarified septic effluent to the absorption system, extending its life. Don't worry about starving the biomat by filtering the septic effluent. There are still plenty of nutrients in the effluent passing into the absorption system.

A number of companies sell these devices which will add life to your drainfield by reducing the level of suspended solids flowing out of the tank. If you buy a septic tank outlet filter you'll see that the filter product will typically be of about the dimensions of the outlet tee I cited above, or perhaps an inch or two deeper. See the links below for more information about septic filters and septic media filter systems. [Photo courtesy of thenaturalhome.com - see Product Source List below]

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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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More Information on Building Diagnostic Inspections and Repairs

• The Septic System Information Website home page for this topic
• Septic Systems Inspection, Testing, & Maintenance- online textbook. Detailed how to inspect, maintain, repair information
• The Home Buyer's Guide to Septic Systems
• Septic Tank Pumping Guide: When, Why, How to pump the septic tank
• Home & Outdoor Living Water Requirements
• Septic Tank Capacity vs Usage in Daily Gallons of Wastewater Flow, calculating required septic tank size, calculating septic tank volume from size measurements
• How Big Should the Leach Field Be? - table of soil percolation rate vs. field size
• Septic System Drainfield Absorption System Biomat Formation - what leads to drain field clogging and expensive drainfield repairs
• Table of Required Septic & Well Clearances: Distances Between Septic System & Wells, Streams, Trees, etc.

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