Do food waste disposers really waste water? Certainly disposers use water, which helps transport ground food through plumbing and sewers. But just how much water is needed? Is it a lot of water?
In short, no. Disposers account for only about 1% of a household’s daily use of water, or the amount of single toilet flush. Given that low amount, disposers are not even referenced in graphical displays of household water use provided by the AWWA.
What Studies Say About Disposers and Water Use
A review of ten studies found that water consumption for food waste disposers is less than five (5) liters per household each day. The five liter per household conclusion is the typical finding of half of the studies. The other half concluded that water use decreased where disposers are used, or no statistically significant difference in water consumption could be associated with their use. Further, one recent study by Aquacraft determined that residential disposers save 13 gallons per household per day water and suggested they should not be considered “water wasting appliances” .
How can this be? Well, typical flow rates for residential plumbing in the kitchen is about 1.5 gallons per minute. Consider that most people use their disposer only three to four times a day for 10 to 15 seconds each time and it’s easy to see why water usage is low compared to most plumbing fixtures – toilets, showers, washing machines, etc.
(30 to 60 seconds) x 1.5 gpm = 0.75 to 1.5 gallons per day
Water Use Statistics from Various Studies
1 gal/capita/day 
3-6 L/household/day 
1.01 L/person/day 
3-4.5 L/person/day 
4 L/person/day 
 DeOreo, William B., Peter Mayer, Leslie Martien, Matthew Hayden, Andrew Funk, Michael Kramer-Duffield, and Renee Davis. 2011. “California Single-Family Water Use Efficiency Study.” Aquacraft, Inc. Water Engineering and Management.
 New York City Department of Environmental Protection. June 1997. “The Impact of Food Waste Disposers in Combined Sewer Areas of New York City.”
 Karlberg, Tina and Erik Norin. VA-FORSK REPORT, 1999.“Food Waste Disposers-Effects on Wastewater Treatment Plants. A Study from the Town of Surahammar.”
 Bolzonella, David, Paolo Pavan, Paolo Battisoni, and Franco Cecchi. Department of Science and Technology. University of Verona. 2003. “The Under Sink Garbage Grinder: A Friendly Technology for the Environment.”
 CECED – European Committee of Manufacturers of Domestic Appliances. Spring 2003. “Food Waste Disposers – An Integral Part of the EU’s Future Waste Management Strategy.”
 Waste Management Research Unit – Griffith University. August 1994. Executive Summary. “Economic and Environmental Impacts of Disposal of Kitchen Organic Wastes Using Traditional Landfill – Food Waste Disposer – Home Composting.”
These studies, and more, are available here and here. Happy Holidays everyone!