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Greywater or Gray water systems as Components of Alternative Septic Systems for Difficult Sites SepticAPedia © Enter your search terms Submit search form   Search This Website - InspectAPedia.com

• Graywater systems as components of alternative septic design
• Graywater system products & designs
• How to install & use graywater systems to conserve water or relieve septic system loading

Greywater is wastewater which does not contain sewage, typically coming from building sinks, showers, and laundry facilities. Graywater systems can reduce the load on or size of a septic system, and gray water separation, filtration, storage, and piping systems can conserve water, for recycling for various uses such as flushing toilets, landscaping, or irrigation. This article describes alternative graywater systems and designs, lists gray water (or grey water) products and suppliers, and compares products, models, and features.

We also include links to greywater system references and books. Shown here is a clean design for onsite greywater disposal using a sketch from Clivus Multrum (see links below). Other greywater systems include incineration and alternative greywater disposal methods. The EcoJohn Jr. shown below at our list of product sources uses a low-flush toilet (not a waterless toilet). This particular toilet is an incinerating unit not a composting toilet. 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.

What is Greywater or Graywater and What is Blackwater?

"Greywater Septic Systems" refer to onsite wastewater systems which reduce the liquid effluent load on a septic system by separating greywater (or graywater) from sinks and showers from blackwater (black water from toilets. When we inspect a home which uses a separate drywell to handle greywater we presume that the owners discovered that their septic system, or at least its leach field, was of limited capacity or life. Gray water systems may also be used to conserve and recycle water in areas of limited water supply. The graywater filter basin and graywater filter shown above are discussed at SEPTIC & GREYWATER FILTERS

Gray water is usually water from building drains other than toilets, such as water from a laundry system, sink, or shower, and effluent from sump pumps. Other site gray water (or greywater) which is sometimes preserved and used at a building includes rainwater or roof runoff. Some writers include groundwater in the greywater category. I disagree, though greywater disposal systems may benefit the environment by replenishing groundwater.

Greywater does not contain human waste products. Therefore when it is disposed-of on-site, it does not need to be treated to the same extent as is required for sewage or "black water". In fact, soil filtration and soil biomat treatment of greywater can produce very clean water for ultimate discharge into the environment. Therefore building code requirements for on-site disposal of grey water are less strict. However in most jurisdictions it is illegal to simply dispose of greywater by dumping it on the ground surface. Some treatment and filtering such as that provided by a drywell will be required.

For building sites where there is limited space for septic "black water" disposal and treatment, one can install piping and equipment separate the gray water from black water (human waste) - a step which reduces the needed size of the septic system. (Space will still be needed for graywater handling).

A second reason that some property owners install graywater handling systems is a shortage of potable water or the need to conserve and recycle water for re-use. In dry areas where there are limitations on the water supply, filtering and treating graywater can permit its use for watering lawns or crops as well as for flushing toilets. This approach serves two goals, both disposing of onsite grawyater and supplying water for crops or shrubs.

A typical graywater system can save 50 to 100 gallons of water a day, or even more, depending on the level and types of water usage in a buildng. Even homes connected to a municipal water supply benefit from a gray water system as by recycling water for re-use the building owners save on their water bill.

The following sample greywater system specification is from: New York State Appendix 75-A.10 Other systems. Other U.S. state's laws and specifications regulating greywater systems are listed below.

(5) Greywater Systems

Greywater [grey water, greay water] systems shall be designed upon a flow of 75 gpd/bedroom and meet all the criteria previously discussed for treatment of household wastewater.

[DF NOTE: Grey water is water that does not include sewage, including water from sinks, showers, and laundry facilities.]

Types of Graywater Products and Systems

Here we outline a variety graywater products, systems, and designs used to conserve water, re-use or recycle water, reduce water use, or to store and re-use graywater. Links to in-depth articles about these products and systems are provided below.

• Cisterns have been used since prehistoric time to collect and store rain water or water from other sources. Modern cistern systems use concrete tanks, steel, fiberglass, plastic, or site built tanks to store water for re-use.
• Composting Toilets reduce water consumption by using little or no water from the building water supply.
• Drywells are used to dispose of un-wanted graywater on-site. There is no provision for water storage or water re-use.
• Filters for Greywater are installed at a laundry sink, clothes washer, or at the outlet of a wastewater tank to filter water for re-use.
• Graywater Irrigation Systems or drip irrigation systems make use of (usually filtered) greywater to provide water to lawns, plants, or crops.
• Low Water Toilets or Low Flush Toilets conserve water by using only a small amount of water to achieve the flush cycle. Low-Water or Low-Flush toilets work well partnered with graywater systems to both conserve and re-use water.
• Rainwater Collection Systems provide alternative water supply for use in flushing toilets or irrigating crops, lawns, or plants. Rainwater collection relieves the load on the potable water supply whether it's from a local well or from municipal supply piping. Rainwater collection systems range from a simple "rain barrell" to collect roof runoff, to very large cisterns which store water for onsite use during dry seasons or droughts.
• Waterless Toilets conserve water by using no water to achieve the toilet flush cycle. Like composting toilets (see above), waterless toilets work well partnered with graywater systems to conserve water. Waterless toilets include incinerating toilet models (see links at page left for more about alternative toilet products & designs.)

Sources for Graywater Products, Systems, Designs, and Model Comparisons

Books and Design Specifications For Graywater Systems: BUY GREYWATER BOOKS ONLINE Create An Oasis with Greywater, Art Ludwig. Also see Ludwig's "Branched Drain Greywater Systems" and his "Building Professional's Greywater Guide". Greywater Recycling Kigs & Equipment from The Natural Home Building Source: http://www.thenaturalhome.com/greywater.html Graywater Central - online web with design information http://www.graywater.net/ Arizona: Graywater Law and Designs: California: Graywater System Standards: www.owue.water.ca.gov/docs/Revised_Graywater_Standards.pdf Colorado: Graywater Design Suggestions: water.state.co.us/pubs/policies/waterharvesting.pdf discusses rainwater harvesting and graywater systems in Colorado New Mexico Graywater Law and Designs Utah: Grayter Systems Design Standards: www.rules.utah.gov/publicat/code/r317/r317-401.htm Eco John describes two incinerating toilet models: EcoJohn Sr - "A highly efficient, waterless toilet that incinerates the waste with propane. This is a toilet that is ideal for cabins, pool houses, guest rooms, or other remote areas where a conventional toilet is not available or too costly to install." and EcoJohn Jr Pr1 System "This is a new revolutionary system that incinerates gray/black water from a holding tank. This system is perfect in areas where a water toilet is needed, but pumping out the waste is problematic or too costly." This grey water and waterless toilet system that includes an incinerator for graywater that marries with a low-water toilet, the the EcoJohn Jr which is includes a sewage and graywater incinerating unit. The EcoJohn Jr. uses a low-flush toilet (not a waterless toilet). This is an incinerating unit not a composting toilet and not a chemical toilet system.

Clivus Multrum greywater systems use a holding chamber, effluent pump, and an onsite irrigation chamber (see our Gravelless septic system components information) to dispose of graywater. The sketch of a greywater handling and disposal system shown here is from the Clivus Multrum website where more details of system operation are provided. Where soil conditions and site space permit onsite graywater disposal this system design can significantly reduce the wastewater load on the septic or "blackwater" system. Clivus Multrum has long experience with composting toilets (CM was an early designer of composting toilets) and greywater disposal systems.

• Contact Us to list your product or service here - if you are a manufacturer of composting toilets or other alternative wastewater treatment system equipment your product may be listed at no fee. Website content critique, additions, and suggestions are also invited.

More Reading and Graywater Systems References, Texts, Pamphlets, Design Guides

BUY GREYWATER BOOKS ONLINE

Graywater and Rainwater System Plans from Ecological Engineering

Technical Reviewers

More expert information on this topic

More Information on Septic System Diagnosis, Maintenance, & Repair

• 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.


Pennsylvania State Fact Sheets relating to domestic wastewater treatment systems include

• Pennsylvania State Wastewater Treatment Fact Sheet SW-161, Septic System Failure: Diagnosis and Treatment
• Pennsylvania State Wastewater Treatment Fact Sheet SW-162, The Soil Media and the Percolation Test
• Pennsylvania State Wastewater Treatment Fact Sheet SW-l64, Mound Systems for Wastewater Treatment
• Pennsylvania State Wastewater Treatment Fact Sheet SW-165, Septic Tank-Soil Absorption Systems
• Document Sources used for this web page include but are not limited to: Agricultural Fact Sheet #SW-161 "Septic Tank Pumping," by Paul D. Robillard and Kelli S. Martin. Penn State College of Agriculture - Cooperative Extension, edited and annotated by Dan Friedman (Thanks: to Bob Mackey for proofreading the original source material.)

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