Washing dishes by hand will use 13-30 gallons of water.
More Info: According to a study published in a 2010 issue of the International Journal of Consumer Studies, measured the difference between the dishwashing habits of 150 participants as compared to their dishwashing habits and calculated that on average, the participants used 13 gallons of water when washing dishes. [Berkholz, 2010]
Washing Habits Dictate the Water Usage
It is difficult to pinpoint exactly how much water is used on average to wash dishes because there are so many variables involved. The total number of gallons will depend on how much water the container used for sudsy water will hold, how many dishes need to be washed, the soil level of the dishes (do they need to be rinsed first), and how long you run the water while rinsing off the dishes. But it’s really not difficult to figure out on an individual basis.
How Much Water Does a Kitchen Sink Hold?
An average size kitchen sink has the capacity to hold nine gallons of water assuming that you leave 3 inches of space at the top.
If you fill your kitchen sink to wash your dishes, you can figure out exactly how much water it takes to fill it. The simple formula is Length x Width x Depth/221.
Let’s assume that you have a double stainless steel sink. You wash dishes in only one basin, so those are the measurements to use.
Depth=9” (Subtract 3-4” because you don’t fill the sink to the top)=6”
TOTAL=1980 cubic inches
The solution will be in cubic inches so you will need to convert a gallon of water to cubic inches, which is 221.
BASIN WATER TOTAL= 8.95 gallons
How Much Water to Rinse Dishes?
Assuming that you have a regular flow faucet in place, running water uses 4 gallons per minute. [US Geological Survey] Energy Star estimates that simply rinsing dishes prior to putting them in the dishwasher uses up to 20 gallons of water. [Energy Star]
RINSING WATER TOTAL=20 gallons
Total the Calculations
Adding the total water to fill the sink with the total running water used to rinse the dishes equates to nearly 30 gallons of water. Using a smaller dishwashing tub, using a low flow faucet head, or running the rinse water conservatively can bring these numbers down.
As you can see, how much water you use will depend on how many dishes you are washing, how large the container is that you fill with sudsy water, and how long you run the water to rinse the dishes.
“How much water do ENERGY STAR dishwashers use? Is there a water-efficiency metric (“water factor”) for ENERGY STAR dishwashers like there is for ENERGY STAR qualified clothes washers?.” ENERGY STAR. N.p., n.d. Web. 13 Mar. 2014. <http://energystar.supportportal.com/link/portal/23002/23018/Article/17719/How-much-water-do-ENERGY-STAR-dishwashers-use-Is-there-a-water-efficiency-metric-water-factor-for-ENERGY-STAR-dishwashers-like-there-is-for-ENERGY-STAR-qualified-clothes-washers>.
“Water questionaire: How much is your daily indoor water use.” Water Science for Schools-US National Geological Survey. N.p., n.d. Web. 13 Mar. 2014. <http://ga2.er.usgs.gov/edu/sq3action.cfm>.
Berkholz, Petra, Rainer Stamminger, Gabi Wnuk, and et. al. “Manual dishwashing habits: an empirical analysis of UK consumers.” International Journal of Consumer Studies 34.2 (2010): 235-242. Print.