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Here is a homeowner's guide to use of garbage disposers or garbage grinders at buildings served by city or municipal sewer systems. Garbage disposal units, also called garbage grinders, food waste disposal units, or garbage disposers add to the solid load in
the septic tank. A garbage grinder is a mechanical grinder which receives food scraps, typically
down a kitchen sink drain, and grinds them into a water/debris slurry that can pass down the
building drain. Both electric and water-powered garbage grinders are available.
SEWER SYSTEMS vs. GARBAGE GRINDERS - Garbage Disposal Unit Effects on Public Sewer Systems
While garbage grinders are a convenience for the homeowner, the added waste they
place in the septic tank might mean that the septic tank needs to be pumped more often.
Photo courtesy of InSinkErator™. The garbage disposal unit shown is their Evolution Septic Assist(TM) that includes
an enzyme injector for use with private septic systems. However depending on local municipal ordinances regarding use of garbage disposal units in cities and towns, this unit and similar models might be found installed in homes served by municipal sewers as well.
While garbage grinders can cause an added loading on conventional, residential, on-site septic systems,
their use is not necessarily bad in municipal sewer systems according to some researchers, as indicated
in the article abstract quoted below. Other studies of the effects of garbage disposers on municipal
sewers have been conducted by various groups including the University of Wisconsin, Delft University Netherlands, and
the Cooperative Research Centre, in Sydney, Australia, and the New York City Dept. of Environmental Protection
Most cities served by municipal sewers `in the U.S. permit the use of garbage disposals
and some cities require their use. Using a kitchen disposer or grinder in cities served by a municipal sewer
reduce the volume of organic waste which otherwise has to be hauled to a landfill. Cities in the U.S. and
other countries are inconsistent in their view of the use of garbage disposers. New York City now (since 1977) permits
their use on residential buildings. Austin Texas has a rebate program to convert garbage disposer use in food service
businesses to a scrap bin system.
Rules for Use of Garbage Disposers in New York City
New York City, which used
to prohibit the use of these devices legalized their use in 1997, out of concern for the increasing volume
of garbage in the city, and in the face of inconclusive test results about their effect on the sewer system.
There has been episodic debate over the question of whether or not garbage disposals clog municipal sewer lines & systems. The New York Times reported in2009 that a New York City ban on residential disposals in effect from 1971 was lifted in 1997 after a two year test convinced the NYC DEP that in New York City residential garbage disposals were not causing a problem. In New York City restaurants are prohibited from using garbage grinders and disposal units, and co-ops and condominium boards are allowed to restrict their use as well.
According to Bolzonella et als., "The use of garbage grinders is not a usual practice in Europe, but it is in other countries around the world (e.g., North America, Japan and Australia). Sometimes, garbage grinders are accused of producing problems in sewers and wastewater treatment plants and are prohibited by environmental protection laws. In this study, the different impacts determined by the use of this technology were considered to show the positive impacts of its use.
In particular, it was shown that garbage grinders enable the disposal of household organic wastes with advantages for the wastewater treatment processes because of an increase in the carbon/nutrients ratio in the wastewater. This is particularly important for biological nutrients removal processes. Daily specific contributions for person equivalent (PE) due to organic waste disposal through garbage grinders were found to be equal to 75 gCODPE(-1) d(-1) for carbon (as COD), 2.5 gNPE(-1) d(-1) for nitrogen and 0.25 gPPE(-1) d(-1) for phosphorous, respectively.
determined a value of 30 for the COD/N ratio. Moreover, no problems with solids settling in sewers were noted. These results were extensively compared with literature data. The economical balance showed that the use of garbage grinders allowed a global saving of some 17 Euro year(-1) for a three people family. Important benefits are also gained from an environmental point of view (e.g., organic wastes disposal nutrients removal in wastewater treatment and increase in biogas production with energy reclamation)."
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FAQs below discusses field reports of problems & solutions for this topic
Frequently Asked Questions (FAQs) About garbage disposer systems
Question: replacing the garbage disposer upper rubber splash guard or sound baffle
What is the rubber fingered insert called that goes in the top of disposals to prevent food debris from splashing back and discourages utensils from falling in? -
the garbage disposer part you are asking about is described as a garbage disposer upper rubber splash guard and stopper or in some repair parts lists for garbage disposers it's called the rubber sound baffle/splash guard.
If you are replacing this part you should order both the new disposer splash guard and a new disposer stopper at the same time so that both parts fit nicely with minimum leakage.
According to our own research, replacement garbage disposer stoppers cost less than $10. U.S. and are availagble to fit just about every unit including, for example: Legend, WasteKing, Sinkmaster, Bone Crusher, and Whirlaway disposals that have the "EZ mount" system, except batch feed models which need to use a different stopper. 
To find these parts online just search on "garbage disposer replacement parts" or take a look at the parts explosion in your own garbage disposer installation manual. If you have that document you will also find a part name, part number, and usually an 800 - telephone number for ordering OEM replacement parts from your own garbage disposer manufacturer.
Watch out: on some garbage disposers including Waste King, to replace the splash guard you may need to disassemble and replace the sink bottom mounting flange assembly. On other models the rubber splash guard is a press-fit part.
Watch out: the rubber splash guard is just that - a splash guard. It is not an assurance that a spoon or other utensil won't fall into and smash up the garbage disposer internals.
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Questions & answers or comments about garbage disposers/grinders
Use the "Click to Show or Hide FAQs" link just above to see recently-posted questions, comments, replies, try the search box just below, or if you prefer, post a question or comment in the Comments box below and we will respond promptly.
 Waste King garbage disposer product specifications, Anaheim Manufacturing
4240 E. La Palma Avenue • Anaheim, California 92807
www.wasteking.com, and also garbage disposer replacement parts list, web search 08/11/2010, original source: Waste King disposer parts, http://www.plumbingsupply.com/disposer.html
 New York Times: "Bigger Muscle for the Disposal", Jay Romano, New York Times, 2/26/2009 p. D2.
Onsite Wastewater Treatment Systems Special Issues Fact Sheet 2 EPA 625/R-00/008 - original citation: http://www.epa.gov/nrmrl/pubs/625r00008/html/fs2.htm
Andress, S., and C. Jordan. 1998. Onsite Sewage Systems. Virginia Polytechnic Institute and State University, Department of Civil Engineering, Blacksburg, VA.
Hazeltine, T.R. 1951. Addition of garbage to sewage. Water & Sewage Works, pp. 151-154. Annual compilation, 1951.
Jensen, P.D., and R.L. Siegrist. 1991. Integrated Loading Rate Determination for Wastewater Infiltration System Sizing. In Proceedings of Sixth Onsite Wastewater Treatment Symposium. American Society of Agricultural Engineers, St. Joseph, MI.
Mancl, K.M. 1998. Septic Tank Maintenance. Ohio State University Extension publication AEX-740-98. Ohio State University, Food, Agricultural and Biological Engineering, Columbus, OH.
Rawn, A.M. 1951. Some effects of home garbage grinding upon domestic sewage. American City, March, pp.110-111.
Siegrist, R.L. 1987. Hydraulic Loading Rates for Soil Absorption Systems Based on Wastewater Quality. In Proceedings of the Fifth Onsite Wastewater Treatment Symposium. American Society of Agricultural Engineers, St. Joseph, MI.
Siegrist, R.L., D.L. Anderson, and J.C. Convene. 1984. Commercial Wastewater Onsite Treatment Symposium. American Society of Agricultural Engineers, St. Joseph, MI.
Stuth, W.L. 1992. Treating Commercial High-Strength Waste. In Proceedings of Seventh Northwest On-Site Wastewater Treatment Short Course. University of Washington, Seattle, WA.
Tyler, E.J., and J.C. Converse. 1994. Soil Acceptance of Onsite Wastewater as Affected by Soil Morphology and Wastewater Quality. In Proceedings of Seventh Onsite Wastewater Treatment Symposium. American Society of Agricultural Engineers, St. Joseph, MI.
University of Wisconsin. 1978. Management of Small Waste Flows. USEPA/600/2-78-73. September, 1978. U.S. Environmental Protection Agency, Office of Research and Development, Cincinnati, OH.
"[The] under sink garbage grinder: a friendly technology for the environment",
Bolzonella D, Pavan P, Battistoni P, Cecchi F.,
Department of Science and Technology, University of Verona, Strada Le Grazie 15, I-37134 Verona, Italy, Environmental Technology, 2003 Mar;24(3):349-59, abstract and article also available from the U.S. NIH at
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.)
Books & Articles on Building & Environmental Inspection, Testing, Diagnosis, & Repair
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