A dishwasher is a mechanical device for cleaning dishes and eating utensils. Dishwashers can be found in restaurants and private homes.
- According to researchers, a load of dishes cleaned in a dishwasher requires 37 percent less water than washing dishes by hand. However, if you fill the wash and rinse basins instead of letting the water run, you'll use half as much water as a dishwasher would.
- 80 percent of the energy your dishwasher uses is for heating water. Remember-by saving water, you're also helping your city's wastewater facility save on the energy used to pump it, treat it, and clean it. Up to 50 percent of a typical city's energy bill goes to supplying water and cleaning it after use!
- Select a dishwasher with a booster heater that raises incoming water to 140° F or higher.
- Avoid using the "rinse hold" setting on your dishwasher. This feature uses 3 to 7 more gallons of hot water for each use. Never use "rinse hold" for just a few dirty dishes. Instead consider the old-fashioned hand wash/rinse basin option.
- Use short wash cycles for everything but the dirtiest dishes. They use less energy and work just as well.
- If your dishwasher has an air-dry setting, choose it instead of heat-drying.
- Many newer dishwashers do not require you to rinse dishes off before loading. If you prefer to pre-rinse use cold water on your dishes before loading them-but don't waste water by letting it run continuously.
- If you have a choice, install your dishwasher away from your refrigerator. The dishwasher's heat and moisture increase your refrigerator's energy consumption. If you have to put them next to each other, place a sheet of foam insulation between them.
- Check the manual that came with your dishwasher for the manufacturer's recommendations on water temperature; many have internal heating elements that allow you to set the water heater to a lower temperature.
- Scrape, don't rinse, off large food pieces and bones. Soaking or prewashing is generally only recommended in cases of burned-on or dried-on food.
- Be sure your dishwasher is full, but not overloaded.
- Don't use the "rinse hold" on your machine for just a few soiled dishes. It uses 3 to 7 gallons of hot water each time you use it.
- Let your dishes air dry; if you don't have an automatic air-dry switch, turn off the control knob after the final rinse and prop the door open a little so the dishes will dry faster.
- To make more efficient use of your dishwasher, only run it when there is a full load.
- If you are shopping for a dishwasher, ensure you purchase a model with an Energy Star symbol.
 How dishwashers work
Unlike manual dishwashing, which relies largely on physical scrubbing to remove soiling, the mechanical dishwasher cleans by spraying hot (55–65 degrees Celsius or 130–150 degrees Fahrenheit) water on the dishes. A mix of water and detergent is used for cleaning purposes, followed by clean water to remove the detergent residue. Some dishwashers have multiple wash and rinse periods within the complete cycle. In some dishwashers, a rinsing aid can be added to the rinse cycle.
 Manual dishwashers
The word 'dishwasher' (or abbreviated as simply "dish") may also refer to a person who washes dishes in a restaurant, hotel or other private or commercial setting. Pots and pans are also washed by hand by scrubbing them in a detergent and water mix, immersing them in a rinse of plain water, and then immersing them in a water/sanitizer solution for a period. Silverware is washed by placing loose silverware in a tray, washing them several times like this, then sorting them into circular holders, and washing them again in the dishwasher. Colloquially, a dishwasher may be known as a pan-diver, from the french "plongeur", and made famous by George Orwell in Down and Out in Paris and London. Commonly used also is the term "KP" for Kitchen Porter or Kitchen Police, who would have a variety of other duties.
The international standard for the capacity of a dishwasher is expressed as standard place settings. Dishes or plates of irregular sizes may not fit properly in a dishwasher's cleaning compartment, so it is advisable to check for compatibility before buying a dishwasher.
Commercial dishwashers are rated as plates per hour. The rating is based on standard sized plates of the same size. The same can be said for commercial glass washers, as they are based on standard glasses, normally pint glasses.
Dishwashers that are installed into standard kitchen cabinets have a standard width and depth of 60 cm (Europe) or 24 inches (US), and most dishwashers must be installed into a hole a minimum of 86 cm (Europe) or 34 inches (US) tall. Portable dishwashers exist in 45 and 60 cm (Europe) 18 and 24 inch (US) widths, with casters and attached countertops. Dishwashers may come in standard or tall tub designs; standard tub dishwashers have a service kickplate beneath the dishwasher door that allows for simpler maintenance and installation, but tall tub dishwashers have approximately 20% more capacity and better sound dampening from having a continuous front door.
Present-day machines feature a drop-down front panel door, allowing access to the interior, which usually contains 2 pull-out racks (sometimes 3). In older U.S. models from the 1950s, the entire tub rolled out when the machine latch was opened, and loading/removing washable items was from the top, with the user reaching deep into the compartment for some items. Today, "dish drawer" models mimic this style, while the half-depth design eliminates the inconvenience of the long reach that was necessary with older full-depth models.
The inside of a dishwasher, called the tub, can be composed of plastic or stainless steel. Stainless steel tubs resist hard water, provide better sound dampening, and preserve heat to dry dishes faster. They also come at a premium price. Older models used a baked enamel on steel and are prone to chipping and erosion; chips in the baked enamel finish must be cleaned of all dirt and corrosion then patched with a special compound or even a good quality two-part epoxy. All European made dishwasher feature as standard a stainless steel interior, even on low end models. The same is true for a built-in water softeners.
Mid-to-higher end North American dishwashers often come with hard food disposal units, which behave like miniature garbage (waste) disposal units that eliminate large pieces of food waste from the wash water. One manufacturer that is known for omitting hard food disposals is Bosch, a German brand; however, Bosch does so in order to reduce noise. If the larger items of food waste are removed before placing in the dishwasher, pre-rinsing is not necessary even without integrated waste disposal units. Pre-rinsing under a running tap beforehand uses more water and is not required.
Many newer dishwashers feature microprocessor-controlled, sensor-assisted wash cycles that adjust the wash duration to the quantity of dirty dishes (sensed by changes in water temperature) or the amount of dirt in the rinse water (sensed chemically/optically). This can save water and energy if the user runs a partial load. In such dishwashers the electromechanical rotary switch often used to control the washing cycle is replaced by a microprocessor but most sensors and valves are still required to be present. However, pressure switches (some dishwashers use a pressure switch and flow meter) are not required in most microprocessor controlled dishwashers as they use the motor and sometimes a rotational position sensor to sense the resistance of water, when it senses there is no cavitation it knows it has the optimal amount of water.
Most dishwashers include a large cone or similar structure in the bottom dish rack to prevent placement of dishes in the center of the rack. The dishwasher directs water from the bottom of the dishwasher up through this structure to the upper wash arm to spray water on the top dish rack. Some dishwashers, including many models from Whirlpool and Kitchenaid, use a tube attached to the top rack that connects to a water source at the back of the dishwasher which allows full use of the bottom rack. Late-model Frigidaire dishwashers shoot a jet of water from the top of the washer down into the upper wash arm, again allowing full use of the bottom rack (but requiring that a small funnel on the top rack be kept clear).
Some dishwashers include a child-lockout feature to prevent accidental starting or stopping of the wash cycle by children. A child lock can sometimes be included to prevent young children opening the door during a wash cycle. This prevents accidents with hot water and strong detergents used during the wash cycle.
 Sound damping
Modern dishwashers are quieter than older models. Using blankets, panels, and sound-absorbing materials in various configurations, dishwashers can achieve sound damping levels down to 39 decibels or so. Undampened, low-end dishwashers generally output noise levels of anywhere from 65–70 decibels. Most manufacturers generally use their own nomenclature with trademark for sound damping.
Different kinds of dishwashing detergent contain different combinations of the items in the list below. Not all of the ingredients below are used in some detergents.
- Dissolves calcium and magnesium ions to prevent 'hard-water' type limescale deposits. Unfortunately, they can cause ecological damage, so their use is starting to be phased out. Phosphate-free detergents are sold as eco-friendly detergents.
- Oxygen-based bleaching agents (older-style powders and liquids contain chlorine-based bleaching agents)
- Breaks up and bleaches organic deposits.
- Non-ionic surfactants
- Lowers the surface tension of the water, emulsifies oil, lipid and fat food deposits, prevents droplet spotting on drying.
- Breaks up and dissolves protein-based food deposits, and possibly oil, lipid and fat deposits. Proteases do this by breaking down the proteins into smaller peptides that are more easily washed away.
- Anti-corrosion agent(s)
- Often sodium silicate, this prevents corrosion of dishwasher components.
Dishwashing detergent may also contain:
- Anti-foaming agents
- Foam interferes with the washing action.
- Additives to slow down the removal of glaze & patterns from glazed ceramics
- Anti-caking agents (in granular detergent)
- Starches (in tablet based detergents)
- Gelling agents (in liquid/gel based detergents)
- Sand (inexpensive powdered detergents)
Dishwasher detergents are strongly alkaline (basic).
Inexpensive powders may contain sand, which can be verified by dissolving the powder in boiling water and then passing the solution through a coffee filter. Such detergents may harm the dishes and the dishwasher. Powdered detergents are more likely to cause fading on china patterns.
 Biodegradable detergent
Besides chemical detergents for dishwashers, biodegradable detergents also exist for dishwashers. These detergents may be more environmentally friendly than conventional detergents.
 Hand-washing detergent
Prior to the invention of the dishwasher in 1886, hand-washing primarily with simple detergents was common. The invention of the machine prompted the use of stronger detergents and rinse agents, thus saving time. Hand-washing dish detergent (washing up liquid) should not be used in a dishwasher, as it will create a large foam of bubbles which will leak from the dishwasher. If hand-washing detergent is accidentally used, the foam may be removed by spraying with salt, and the dishwasher should be forced into a drain cycle to remove the detergent and water.
 Hazing of glassware, prohibition on dishwashing lead crystal
Glassware washed by dishwashing machines can develop a white haze on the surface over time. This may be caused by any or all of the below processes, only one of which is reversible:
 Limescale deposit
If the dishwasher has run out of the salt that recharges the ion exchange resin that softens the water, and the water supply is "hard", limescale deposits can appear on all items, but are especially visible on glassware. It can be removed by cleaning with vinegar or lemon juice, or a proprietary limescale removal agent. The dishwasher should either be recharged with salt, adjusted appropriately for the hardness of the supply water—or possibly this is a symptom of failure of the ion exchange resin in the water softener (which is one of the more expensive components). The resin may have stopped working because it has been poisoned by iron or manganese salts in the supply water.
 Silicate filming/etching/accelerated crack corrosion
This film starts as an iridescence or "oil-film" effect on glassware, and progresses into a "milky" or "cloudy" appearance (which is not a deposit) that cannot be polished off or removed like limescale. It is formed because the detergent is strongly alkaline (basic) and glass dissolves slowly in alkaline aqueous solution. It becomes less soluble in the presence of silicates in the water (added as anti-metal-corrosion agents in the dishwasher detergent). Since the cloudy appearance is due to nonuniform glass dissolution, it is (somewhat paradoxically) less marked if dissolution is higher, i.e. if a silicate-free detergent is used; also, in certain cases, the etching will primarily be seen in areas that have microscopic surface cracks as a result of the items' manufacturing. Limitation of this undesirable reaction is possible by controlling water hardness, detergent load and temperature (see Maytag Web site, Troubleshooting on Filling the standard tub detergent dispenser). The type of glass is an important factor in determining if this effect is a problem. In hard-water areas more detergent is needed to help prevent etching, and some dishwashers can reduce this etching effect by automatically dispensing the correct amount of detergent throughout the wash cycle based on the level of water hardness programmed. GE Appliances website
 Physical abrasion
Glassware placed such that it is physically touching can abrade and produce a milky surface.
Components found in dishwasher detergents can chemically scour the glass, causing tiny crystals, which can precipitate further crystal growth that can turn entire glasses cloudy
Lead crystal should not be cleaned in a dishwasher as the corrosive effect of dishwasher detergent is high on such types of glass—that is, it will quickly go 'cloudy'. In addition, the lead in the crystal glass can be converted into a soluble form, which could endanger the health of subsequent users.
 Items that should not be put in a dishwasher
Some items can be damaged if washed in a dishwasher because of the effects of the chemicals and hot water. Lead crystal will be irreversibly damaged if put in a dishwasher, while aluminium items will discolour. Saucepan manufacturers often recommend handwashing due to the harsh effects of the chemicals on the pan coatings. Valuable items—such as antiques—should be washed by hand as they may be dulled or damaged, and detergents will gradually fade the glazing and print. Sterling silver and pewter will oxidize and discolour from the heat. Furthermore, pewter has a low melting point and may warp in some dishwashers. Cast iron is likely to rust in a dishwasher.
Items soiled by wax, cigarette ash or anything which might contaminate the rest of the wash load (such as poisons or mineral oils) should not be put in a dishwasher. Objects contaminated by solvents may explode in a dishwasher. Glued items, such as some cutlery handles or wooden cutting boards, may be melted or softened if dishwashed, especially on a hot wash cycle when temperatures can reach 75 °C; these high temperatures can also damage plastic items which are labelled as not being dishwasher safe, however some plastic items can be distorted or melted if placed in the bottom rack too close to an exposed heating element, hence many dishwasher-safe plastic items advise placing in the top rack only (many newer dishwashers have a concealed heating element away from the bottom rack entirely). Squeezing plastic items into small spaces may cause the plastic to distort in shape.
Dishwashers should only be used to wash normal household items, like plates, cutlery, cups, mugs, kitchenware etc. Items such as paintbrushes, tools, furnace filters etc. should not be put into a dishwasher as this will cause the subsequent washes to become contaminated and may cause damage to the appliance.
 Environmental impact
In the European Union, the energy consumption of a dishwasher for a standard usage is shown on a European Union energy label.
 Comparison with washing by hand
Comparing the efficiency of automatic dishwashers and hand-washing of dishes is difficult because hand-washing techniques vary drastically by individual. A 2003 peer-reviewed study concluded that the best automatic dishwashers available at the time, when fully loaded use less electricity, water, and detergent than the average European hand-washer. The most efficient hand-washers in that study, however, were far more energy efficient than the dishwashers. The study does not address costs associated with the manufacture and disposal of dishwashers, the cost of possible accelerated wear of dishes from the chemical harshness of dishwasher detergent or the value of labour saved.
 Detergents and rinse aids
Most dishwasher detergent contains complex phosphates, as they have several properties that aid in effective cleaning. However, the same chemicals have been removed from laundry detergents in many countries as a result of concerns raised about the increase in algal blooms in waterways caused by increasing phosphate levels (see eutrophication). The state of Maryland, USA, is considering a bill to limit phosphates in dish detergent to help clean up the Chesapeake Bay.
In addition, rinse aids have contained nonylphenol and nonylphenol ethoxylates. These have been banned in the European Union by EU Directive 76/769/EEC.
 Other environmental factors
If hand-washing also allows the dishes to air-dry, then the energy usage is going to be very different; consideration also has to be given to how the water for hand-washing is heated - an efficient gas boiler in a cold climate (where waste heat also usefully heats the building) will be better than an electric heater (or the electric heater in the dish washer). Looking at the wider picture, there are also energy and pollution costs in manufacturing the dish-washer and the disposal or recycling of the unit when it reaches end of serviceable life.
 Is it OK ... to use a dishwasher?
They beat us at chess. They make better LBW decisions than us. And they even milk cows faster than we can. Are there any Man v Machine challenges left that we'd back ourselves to win these days?
Not too many of us are going to grumble, though, at the news that, in what should be more accurately described as Marigold v Machine, we come a poor second when it comes to using less water and energy to wash up our dirty dishes. Or so says Rainer Stamminger, the professor of household and appliance technology at the University of Bonn. In 2004, he and his team published one of the most detailed studies ever into whether dishwashers are more efficient than handwashing. His conclusion was that, if used correctly, machines are far better. Cue whoops of joy in kitchens lucky enough to have a dishwasher.
Not so fast. What Stamminger's results actually show is that the most efficient dishwashers on the market use less energy and water than the most slap-dash human dishwashers. In between these two extremes matters become a little less clear cut. It's worth looking at the testing method quickly to see how the results can vary.
Following the accepted European standard for testing dishwasher performance and consumption (these things are taken very seriously), 12 place settings of dishes totalling 140 individual items including china, glasses and cutlery are soiled with seven types of stubborn foodstuffs: spinach, minced meat, oak flakes, milk, tea, egg yolk, and margarine. Easy, you say? Well, then the dirty dishes are normally placed in an oven and dried for two hours at 80C to make sure the food debris is well and truly caked on. But Stamminger thought the test too unfair on the lowly human tester, so he changed it: the dirty dishes were left to air dry for two hours instead. Then 113 people from seven European countries were placed in front of two sinks with hot and cold taps, a variety of cleaning tools and 22 detergents to choose from, and told to wash and dry the dishes as they would at home.
What his team noticed was that there was a huge difference in techniques, that included pre-soaking everything, washing each item under running hot water, and rinsing in a bowl of cold water. On average, though, the 113 human washers each used 103 litres of water (roughly equal to a two-thirds full bath) and 2.5kWh of water-heating energy, taking 80 minutes to complete the task. (Incidentally, the Brits were only beaten by the Germans in terms of having the most efficient techniques; the Spanish and Portuguese were by far the most wasteful.) By comparison, the machines used 15 litres of water and 1-2kWh of electricity, taking between 80 and 160 minutes.
But what the study also revealed was that we can just about compete with the machines if we follow the right hand-washing technique. The best testers were only using 30 litres of water and 1kWh of energy. Stamminger identified the following successful traits: scraping, not rinsing, food scraps from dishes; not pre-rinsing all the dishes under a running tap; using two sinks, one filled with hot water and detergent, the other with cold for rinsing; and not over or under using detergent.
However, Stamminger didn't examine the considerable amount of energy and materials required to make and transport the dishwasher. He also didn't consider the environmental impact of the detergents. For example, many dishwasher tablets use phosphates to help with anti-scaling which then contribute to the process of eutrophication, whereby over-production of algae in water leads to lack of oxygen for aquatic life.
But as with handwashing, there are techniques to make a dishwasher even more efficient. You can save energy by stopping it before the drying cycle ends, and letting it air dry instead. And you can save water and effort by not rinsing dishes under a tap beforehand. It is also important to only run the machine with a full load and to use the economy settings where possible.
 What are the Best Eco-Friendly Dishwasher and Laundry Soaps?
 What are the best kinds of dishwasher and laundry soaps to use in consideration of where all the wastewater goes after use?
The average North American produces between 60 and 150 gallons of wastewater every day, much of it a result of washing dishes and clothes. Municipal water treatment facilities do their best to filter out the synthetic chemicals common in most mainstream dishwasher and laundry soaps, but some of these pollutants inevitably get into rivers, lakes and coastal areas, where they can cause a wide range of problems.
 Dishwasher and Laundry Soaps Can Pollute Water, Cause Harmful Algae Blooms
Perhaps the most worrisome of these pollutants, phosphates, can cause large build-ups of algae and bacteria that rob water bodies of oxygen and thus choke out other life forms. In response to just such a problem occurring in Lakes Ontario and Erie in the late 1960s and early 1970s, the U.S. and Canada signed the Great Lakes Water Quality Agreement in 1972. The agreement banned the use of phosphates in laundry detergents and dish soaps used in the region, and resulted in a significant decrease in algae blooms throughout the Great Lakes.
 Chemicals in Dishwasher and Laundry Soaps Pose Health Risks
Despite the success of the agreement, phosphates and other synthetic chemicals continue to be widely used in laundry and dish soaps throughout the world. Aside from their effect on water bodies, these ingredients also trigger allergies, irritate the skin and eyes and carry other health risks.
 Consumers Can Choose Eco-Friendly Dishwasher and Laundry Soaps
Fortunately, consumers now have more environmentally friendly choices than ever. Companies such as Seventh Generation, Ecover, Bioshield and Naturally Yours make safer dishwasher and laundry soaps that do not contain phosphates or other harmful synthetic chemicals. Many of these greener options are available at retail stores like Whole Foods and Wild Oats as well as online from websites like Kokopelli’s Green Market and a host of others.
 Check Ingredients in Dishwasher and Laundry Soaps
According to Seventh Generation CEO Jeffrey Hollender, consumers interested in doing the right thing for the environment should look at ingredients, not slogans. “Just because a product says it is natural doesn’t mean it is nontoxic,” he says. Environmentally friendly ingredients to look for include grain alcohol, coconut or other plant oils, rosemary and sage. Synthetic ingredients to avoid include butyl cellosolve, petroleum, triclosan and phosphates. It is also best to avoid detergents that employ fragrances, as they can contain chemicals known as phthalates that have been linked to cancer.
 Mix Your Own Eco-Friendly Dishwasher and Laundry Soaps
Although household-cleaning chores can often be accomplished with non-toxic, homemade alternatives—such as water mixed with borax, lemon juice, baking soda, vinegar or washing soda—laundry and automatic dishwashing soaps are not so easily replaced with home concoctions. However, Emily Main, senior editor at The Green Guide, recommends adding one-quarter cup of baking soda or white vinegar to clothes washes to act as a fabric softener, and for stain removal suggests soaking fabrics in water mixed with either borax, lemon juice, hydrogen peroxide or white vinegar. As to home recipes for dishwashing, some hardcore homesteaders recommend trying an equal mix of borax and baking soda, but this is probably best used only in a pinch as the abrasiveness of such a mixture can scratch glassware over time.