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Many people, according to the Internet, believe that dishwashers fill to the brim with water, making a swimming pool for dirty dishes. In reality, however, a dishwasher is closer to a car wash than a swimming pool.
Whether you’re trying to fix a misbehaving dishwasher or just curious, let’s take a closer look at what happens inside a dishwasher.
Dishwashers pump fresh hot water into the wash cavity and drain between each cycle, wash, rinse and heat dry. They do not use the same water over and the heat dry raises the temperature over the boiling point scalding the dishes to sanitize the dishes.
Final wash and rinse
This part pulls in new, clean water and begins the heating/spraying/filtering/heating cycle anew. Just like the main wash, the heater is eventually shut off while the spraying continues.
The final wash/rinse may or may not use detergent. Like the main wash, the final wash/rinse can take 20 to 60 minutes and may repeat multiple times throughout the cycle duration.
A graph of the temperature inside the dishwasher over time clearly illustrates the three main parts of a cycle:
Theres one caveat worth mentioning here. Some dishwashers do not have built-in water heaters—they pull water directly from the source, so whatever temperature water happens to be circulating in the kitchen is the water that gets used to clean the dishes.
Washing with cold water may be the culprit behind unclean dishes or undissolved detergent pods. If this is the case, try running hot water at the kitchen sink (to purge the cold water from the system), then turn off the faucet once the dishwasher cycle starts. If the hot water at the kitchen sink stays on, it will pull hot water away from the dishwasher when it needs it most.
Depending on the manufacturer, additional rinses, heated drying to get your dishes dry, or other features may also happen, but pre-wash/rinse, main wash, and final wash/rinse are the core components of your dishwashers cleaning cycle.
The importance of hot water
One of the key parts of clean, sanitized dishes is hot water. Water temperatures inside a dishwasher get as high as 130°F-140°F. The heating doesn’t happen instantaneously, however. The dishwasher pulls in water from your water supply via its external hookup.
When a cycle starts, water is pumped into a pool at the bottom of the dishwasher. The heating element at the bottom turns on, heating the water.
At the same time, the water in that pool is mixed with the detergent and sent into the spray arms found throughout the dishwasher, typically at the bottom and top of the dishwasher and occasionally beneath the top rack. The water surges through the spray arms, and hits the dirty dishes, hopefully taking some nasty food stains with it.
The dirty water eventually drips back into the pool below, where it is filtered, reheated, and sent back out into the spray arm again. The same water is being constantly used and reused, heated and reheated, sprayed and collected. See? Its much more like a carwash than a swimming pool (at least my swimming pool).
Once the water hits the desired temperature, the heater turns off, but the pumps continue pushing water through the spray arms. At the end of that portion of the wash cycle, all of the water is drained (that’s the gurgling sound you sometimes hear your dishwasher make), clean water takes its place, and the cycle begins anew.
So now that you know how a dishwasher works, we can dig into what actually happens during a modern dishwasher cycle.
VERIFY: Does running the dishwasher every day save water?
FAQ
Do dishwashers reuse the same water?
Do all dishwashers use the same amount of water?
Is it cheaper to wash dishes by hand or dishwasher?
Does using a dishwasher really save water?
Are dishwashers more efficient than hand washing?
Yes In terms of water and energy usage, dishwashers are much more efficient than washing dishes by hand. According to a recent study by detergent brand Cascade, it takes the average person about 15 seconds to handwash a dish. During that time, the sink uses half a gallon of water (a typical faucet spouts four gallons of water every two minutes).
How much water does a dishwasher use?
During that time, the sink uses half a gallon of water (a typical faucet spouts four gallons of water every two minutes). By comparison, an Energy Star-certified dishwasher uses less than four gallons per cycle, which means running a load with as few as eight dishes can actually save water.
Does a dishwasher clean dishes and utensils at the same time?
A dishwasher cleans dishes and utensils at the same time without wasting any water, explains Tompson. “It also heats the water beyond what a person could stand, which cleans everything more quickly,” Tompson says.
Does a dishwasher save water?
Using a dishwasher does save water. A modern dishwasher uses about three to four gallons of water compared to up to 27 gallons when washing the same amount of dishes by hand,” says Jeremy Tompson of YouthfulHome, a cleaning services specialist. “Older dishwasher models may use as much as 15 gallons of water—but that’s still less than handwashing.”