Using Septic Filters and Graywater Filters to Protect Drainfields
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• What are septic filters?
• Signs of a clogged septic filter
• Graywater filters
• 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. 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. Citation of this article by reference to this website and brief quotation for the sole purpose of review are permitted. Use of this information at other websites, in books or pamphlets for sale is reserved to the author. Technical review by industry experts has been performed and is ongoing - reviewers welcomed and are listed at "References." © Copyright 2008 Daniel Friedman, All Rights Reserved. Information Accuracy & Bias Pledge is at below-left. Use the links at page left to navigate this document or to go to Other Website Topics. Green links at left show where you are in our document & website.

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.