How Steam Dishwashers Work


Want to blow off some steam about your old dishwasher? New dishwashers use steam itself as a cleaning agent.
Want to blow off some steam about your old dishwasher? New dishwashers use steam itself as a cleaning agent.
©iStockPhoto/Can Balcioglu

Believe it or not, the modern world largely runs on steam. Most people associate steam power with antiquated steam boats and the Industrial Revolution of the 19th century, but the truth is, many of today's power plants still rely on it. Whether it's a fossil-fueled or nuclear power plant, its process involves heating water to its gaseous state -- steam -- to turn a turbine and create electric power. But simple steam also has more hands-on modern uses.

For instance, one of the most common ways we use steam in our daily lives is in ironing our clothes. When an iron infuses fabrics with steam, wrinkles disappear. Steam also is a fast (though all-too-temporary) cure for congestion from the common cold. By loosening mucous, the steam allows it to easily drain, which opens air passages. Aside from these home uses, steam also can effectively sanitize things with its high temperatures. Hospitals, where cleanliness is paramount, use steam in pressurized mechanisms to thoroughly sterilize their instruments.Why not use that same sterilizing power in the home? That's precisely the idea behind the advanced steam dishwasher, a follow-up to steam washers and dryers.

For many people, traditional dishwashers are a pain. If you don't rinse your dishes in the sink before you load them into the dishwasher, you may find food dried onto your dishes and flatware when you unload. This prewashing largely defeats the water-, time- and energy-saving benefits of a dishwasher. Not only that, but rigorous dishwashers may swish your precious heirloom china into bits.

Today, the added features of steam dishwashers are supposed to eliminate these traditional dishwasher pitfalls. Namely, steam provides a powerful cleaning cycle that's also gentle on fine china.

In the next few pages, we'll investigate these state-of-the-art dishwashers and find out how steam fights grime.

­­

The Dirt on Steam Cleaning Dishwasher Technology

Steam can help a dishwasher sterilize dishes.
Steam can help a dishwasher sterilize dishes.
Maytag

Aside from its ability to produce electricity, steam also is a potent cleaning tool. If you've ever steam-cleaned your carpets, you know how powerful it can be compared with vacuuming. Using the same principles, steam dishwashers use high-pressure, high-temperature steam to help separate food from dishes, cups and flatware. The pressure of a gas indicates how much force it exerts on surfaces. The tighter gas molecules are packed together or the hotter they are, the harder they hit surfaces.

To understand why steam is so effective, let's take a look at some of its special properties:

  • Steam can contain a lot of heat: Have you ever hungrily peeled off the cover of food that's been heated in the microwave, only to be burned by the steam that rushes out? If you have, you know that steam can get very hot -- even hotter than water. At normal atmospheric pressures, water can only get as hot as about 212 degrees Fahrenheit (100 degrees Celsius). At that point, it turns to steam. The steam, in turn, can carry a lot of heat and, if pressurized, can continue to heat up, which enables it to sanitize objects.
  • Steam expands to a bigger volume than water: As water heats up and turns to steam, it can expand and take up more space than the water did. This fact means that a little bit of water can create a lot of steam -- and conduct a lot of cleaning work. In the end, you've used less water to get the same (or possibly better) work done.
  • Steam is easily accessible: Because you find "water, water everywhere," you can find the potential for steam everywhere. Just heat water to a high enough temperature and you'll create steam. Steam cleaning doesn't require harmful or expensive cleaning chemicals or detergent to work.

In dishwashers, the high pressure and temperature of steam effectively loosen the strong bonds between muck and your dishes. In this way, steam can break the bonds that even good old-fashioned soap and water couldn't divide. In essence, the food absorbs the steam, which in turn rehydrates the dried, baked-on food so that it releases its death grip on the dish. After breaking the waste down, a good rinse will wash it all away. Perhaps most important, though, is that the extremely high temperatures of the steam also kill bacteria and sanitize the dishes.

Because it has sterilizing power, people use steam for a variety of cleaning purposes. For instance, because it can be gentle yet effective, steam is used to clean masonry surfaces like brick and stone. Some people use steam to clean and prepare surfaces to be painted. And, food processing plants that need to clean their equipment will apply steam to rid the instruments of oils and grease. Public city cleaners can even use steam to remove gum from tables and hand rails [source: Sioux Corporation].

On the next page, we'll learn about the steam dishwasher's steam cycle.

Steam Dishwasher Cycles and Options

Steam dishwashers incorporate steam features as an addition to normal cycles.
Steam dishwashers incorporate steam features as an addition to normal cycles.
Maytag

The name "steam dishwasher" might seem misleading. These dishwashers don't exclusively use steam, but steam is an important and effective step in their cycle. Knowing this, skeptics might question the marketing behind calling these new products steam dishwashers. After all, haven't we all seen traditional dishwashers release steam when we open them after a hot wash?

It's true that conventional dishwashers do produce some steam. In fact, some adventurous cooks effectively steam salmon in a dishwasher. However, this steam is mostly just a byproduct of the drying cycle (to dry dishes, dishwashers heat up the air, which converts the leftover water to steam). On the other hand, cutting-edge steam dishwashers actually harness steam's cleaning ability in the washing phase. Specifically, they can either directly heat the water in the tub into steam (as with Maytag models) or incorporate nozzles dedicated to releasing pure, hot, high-pressure steam at the right time (as with LG models).

With the latter nozzle method, steam dishwashers will include a steam generation unit. The unit allows the appliance to heat water into a steam state in a separate section from the main tub. This way, streams of pure steam can release directly from the nozzles to the main tub with the dishes.

Although steam dishwashers don't exclusively use steam as a cleaning method, the user has the option to add a steam cycle to clean a load of dishes. But steam dishwashers can use steam differently and at various times. For instance, some steam dishwashers, such as LG's models, have a special setting that uses steam to clean fragile dishes. Because steam doesn't need to use force to get dishes clean, it's a great tool for cleaning fine china and other easily breakable items. Adding a steam option to other, more rigorous cycles also will help it clean more effectively. It's like adding an extra boost of cleaning power to the traditional cycle.

The GE steam dishwasher includes another option, however. In addition to a normal steam phase, the GE Profile SmartDispense2 model has a cycle to prewash dishes, which is purely a steam bath, so that users don't have to manually rinse dishes prior to loading [source: GE]. Other steam dishwasher models from Maytag offer yet another steam option. Maytag provides what it calls "SteamClean" features. The SteamClean adds 24 minutes to the end of the cleaning cycle during which the appliance inundates the load with high temperature steam and a rinse before drying [source: Maytag].

So are steam dishwashers really superior to regular dishwashers? On the next page, we'll take a look at the good, the bad and the dirty of steam dishwashers.

Steam Dishwashers Performance Tests

Even if the steam wash doesn't impress you, some of the appliance's other features might.
Even if the steam wash doesn't impress you, some of the appliance's other features might.
Maytag

Appliance companies are touting new top-of-the-line steam features as the latest and greatest thing in dishwasher technology. But should we believe the hype? After all, a steam dishwasher can run you up to $1,600 (whereas quality ones can be as little as $650), so it's best to know all the dirty details before making the purchase. Do these dishwashers get your dishes and flatware significantly cleaner?

Consumer Reports performed tests on steam dishwashers to answer that very question. Researchers ran the dishwasher with dirty dishes on steam cycles. Then they ran dishes in the same dishwasher without using the steam options. They found that the addition of steam does in fact make dishes cleaner -- but only a little bit. In the end, they concluded that the difference between steam cleaned and traditionally cleaned dishes was only slight [source: Consumer Reports]. In fact, they found that the spray jet features of some dishwashers worked more effectively than steam (for those dishes that got a front seat to the water blast).

Not only don't these steam dishwashers live up to the cleaning hype, but steam dishwashers typically take a lot longer to get through a full cycle than traditional dishwashers. The steam phase alone can add as much as 45 minutes to the cleaning time [source: Consumer Reports]. One LG steam dishwasher model runs for about two hours and 20 minutes for a full wash with steam [source: Consumer Reports].

But the Consumer Reports editors did grant that, besides the steam features, these cutting edge dishwashers are generally more stylish and easier to use than conventional models. Convenient, adjustable and additional racks are a major plus for these dishwashers. They also happen to be very quiet and energy-efficient appliances. So, even if steam performance, style, convenience and quiet aren't sufficient, the prospect of long-term savings in energy bills might persuade customers that they're worth the money (visit the Energy Star Web site to find out how much a particular model might save you.)

Another incidental advantage is that many new steam dishwashers advertise having a very large capacity. But if you're sick of the traditional, oversized dishwasher and you're in the market for a more space-efficient appliance, the Swash might be right for you. Although the Swash is still in development with an Australian company, Envisage NanoSytems, and is not yet ready for sale, the design is impressive. The Swash is a steam dishwasher that takes up very little space. (The designer hopes it will one day fit on a countertop like a microwave.) It even has a steam setting that requires absolutely no detergent (but rather sanitizes through the high temperature of the steam). Though it's conveniently small, it can fit about four place settings inside. Because it filters and reuses water, it's extremely water efficient. And, as it takes less heat to warm up a smaller volume of water, it's also highly energy efficient [source: DesignBoom].

Want to learn more about your other household appliances? Check into the links on the following page.

Related HowStuffWorks Articles

More Great Links

Sources

  • Consumer Reports. "Consumer Reports' Tests Reveal Dishwashers with Steam are Not So Hot." Consumer Reports. March 2008. (June 18, 2008)http://www.consumerreports.org/cro/cu-press-room/pressroom/archive/2008/03/0803-eng0803dis.htm?resultPageIndex=1&resultIndex=2&searchTerm=steam%20dishwasher
  • Consumer Reports. "LG LDF9810[ST] Dishwasher: First Look." Consumer Reports. March 2008. (June 18, 2008)http://www.consumerreports.org/cro/appliances/kitchen-appliances/dishwashers/first-look-lg-ldf9810st-steam-dishwasher-12-07/overview/first-look-lg-ldf9810st-steam-dishwasher.htm?resultPageIndex=1&resultIndex=8&searchTerm=dishwasher
  • DesignBoom. "Swash: Steam Dishwasher." DesignBoom. (June 18, 2008)http://www.designboom.com/contest/view.php?contest_pk=11&item_pk=7332&p=3
  • GE. "America's Smartest Dishwasher Now Steam Cleans." GE. Press Release. (June 18, 2008)http://www.geconsumerproducts.com/pressroom/press_releases/appliances/dishwashers/SD2dish.htm
  • LG Electronics. "Dishwasher." U.S. Patent 20070079851. Filed Sept. 5, 2006. Pub. April 12, 2007. http://www.freepatentsonline.com/US20070079851.html
  • LG. "Owner's Manual: Dishwasher: Model: LDF9810ST/LDF9810WW/LDF9810BB." LG Electronics. (June 19, 2008)http://us.lge.com/download/product/file/1000003010/MFL30149746_01.pdf
  • Maytag. "Maytag Brand Dishwashers with New "SteamClean" Option Remove Stubborn Residue from Glassware, Dishes." Maytag. Press Release. Feb. 13, 2008. (June 18, 2008)http://maytag.com/assets/pdfs/cms/other/2008_MaytagSteamDishwasher.pdf
  • Sioux Corporation. "Why Use Steam Cleaning Vs. Hot Or Cold Water Washing?" Sioux Corporation. (June 18, 2008) http://www.sioux.com/why-steam.html
  • Whirlpool. "Steam and Efficiency Meet in the Kitchen with New Whirlpool Brand Electric Ranges." Whirlpool. Press Release. Feb. 13, 2008. (June 19, 2008) http://www.whirlpool.com/assets/pdfs/other/PR_2008.02.13_SteamandEfficiencyMeetintheKitchen.pdf

­