What's The Best Way To Wash Dirty Dishes: Dishwasher Or Sink?

Is a machine more eco-friendly or should you scrub them by hand the way grandma used to?

April 1, 2016
dishwasher and a sink
Punchstock/House Proud

You've already stopped doing the 10 Things Most People Do To Pollute Water Without Realizing It, but now you're trying to conserve it as well. Should you clean your plates in the dishwashing machine, or fill the sink with suds and wash them by hand? It’s a question frequently asked by people who want lower their bill, to cope with a drought, or out of concern for the environment.

Related: What Will It Take To Solve The World's Water Problems?

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Hand Washing
Pros: You control the water, so you have a better sense of how much you’re using, as opposed to a machine that uses the same amount of water whether you’re washing 5 dishes or 50. Hand washing your dishes may also allow you to get them a little cleaner, since the mechanics of washing by hand rely entirely on your own brute strength and persistence, and not on the abrasiveness of a detergent or other disinfectant.

Cons: Unless you’re diligent, hand washing can be extremely wasteful. A European study comparing hand washing to machine dish washing found that hand washers used as much as 27 gallons of water and 2.5 kilowatt-hours (kWh) of energy to wash 12 place settings, compared with the 4 gallons and 1.5 kWh used by a hyperefficient dishwasher to wash the same number of dishes.

Related: The Organic Way To Wash Your Car

Dishwasher
Pros: Aside from the time you save, using a machine can save you up to 5,000 gallons of water and $40 in utility costs each year over hand washing, according to the Environmental Protection Agency’s Energy Star program. Energy Star doesn’t currently factor water savings into its ratings, but the agency estimates that most qualified washers use an average of 4 to 6 gallons per load, depending on whether you have a compact model or a full-size model and which wash cycle you use. They do require, though, that Energy Star–rated machines use at least 41 percent less energy than normal washers, and that figure takes into account the energy used by a water heater to heat the water.

 

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Cons: Like hand washing, bad habits can make dishwashing machines very inefficient, for instance, running it when you only have a few dishes inside, or using a more water-intensive wash cycle than you really need. And if you have a really old machine, you could be using as much as 15 gallons per load. Furthermore, unlike the dish liquids you use when hand washing, machine-dishwashing detergents often contain phosphates, chemicals that aren’t removed by wastewater treatment plants and can deprive rivers and streams of oxygen, killing the aquatic organisms that live in them.

Results
So what should you do? Go with the dishwasher. There are many conscientious hand washers out there who are good about saving water, but using a dishwasher fully loaded with a phosphate-free detergent will save you water and energy over the long haul, particularly if you have a newer or an Energy Star–rated machine. Some of the most efficient Energy Star–rated machines are 141 percent more energy-efficient than older dishwashers—an Energy Star washing machine can also help you Be More Eco-Friendly In The Laundry Room.

Nevertheless, there are those times when you’ve got two dishes in the sink and don’t want them smelling up a dishwasher while you wait to get a full load. You can calculate how much water you use to hand wash those with a stopwatch and a simple math equation. Federal standards require kitchen faucets to run at no more than 2.5 gallons per minute (gpm), so using that as a basis:

 

(2.5 gpm X # of minutes it takes to fill the sink) + (2.5 gpm X # of minutes you run the water while rinsing the dishes) = the gallons of water needed to hand wash your dishes.

Compare that with your dishwasher’s gallon-per-load rate, and you’ll have a good sense of when it’s just as water-intensive to hand wash as it is to use a machine. So for example, if your dishwasher uses 5 gallons to clean a load of dishes, you’ll use less water than that if you don’t run the faucet for more than 2 minutes total (including filling the sink, washing, and rinsing the dishes).

How To Make Either Method More Efficient:

Hand Wash

• Don’t leave the faucet running constantly as you soap-up then rinse off each dish.
• If you have a double-basin sink, fill one side with wash water and the other with rinse water. You can reuse the rinse water for each dish, and then reuse it again to water your lawn.
• Aerate! You can increase the efficiency of your rinsing with an aerator that limits output from 2.5 gpm to 1.5 gpm or less (going below 1.5 gpm, however, may be frustrating, given the time it would take to fill up the sink).
• Stop rinsing. In some European countries, water costs are so high that people wash their dishes and then just wipe the sudsy water off, without rinsing.

Dishwasher

• Wait until the dishwasher is completely full before you run it.
• Don’t prerinse. Prerinsing can waste up to 20 gallons per load, according to Energy Star, and completely negates any savings you get from a water-efficient dishwasher. Detergents available today are designed to handle lots of gunk.
• Go phosphate free. Phosphates can be so damaging to waterways that the federal government banned them from laundry detergents in 1994. They’re still legal in dishwashing detergents, although more states are starting to ban that use as well. Look for brands that explicitly state that they’re phosphate free on the label (and, like phosphate-based detergents, are just as good at handling gunk).

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