How does a dishwasher work? In many homes, the dishwasher is an essential kitchen appliance that turns a tedious chore into a simple set-it-and-forget-it task. Dirty dishes go in, and clean dishes come out: It couldn’t be easier! But what actually happens inside the machine when you run the dishwasher?
How a Dishwasher Works
Josephine Cochrane, an Ohio socialite who worked on her invention in a backyard workshop, patented the first automatic dishwasher in 1886. Cochrane’s design was so successful that, almost a century and a half later, modern dishwashers work in much the same way – although we gave up hand-pump power for electricity.
What’s Inside a Dishwasher?
While there are minor differences between the various dishwasher brands and models, most share the same basic design. The casing of the dishwasher is an insulated, water-tight box. Inside the dishwasher are several different structures:
- Metal racks to hold dishes and cutlery.
- Water inlet and outlet pipes.
- A dispenser for detergents.
- An internal heating element that heats water to the correct temperature.
- A basin at the bottom of the dishwasher.
- Rotating spray arms that spray water on the dishes during the wash cycle.
- A control box with internal sensors and timers that regulate the cycle. The control box ensures that each stage in the wash cycle lasts for the correct length of time and in the right order.
The Dishwasher Wash Cycle, Step by Step
So just how does a dishwasher work? The process relies on three essential elements: cleaning agents, heat, and the mechanical wash cycle. Here’s how it all comes together to get your dishes sparkling clean.
Start the Cycle
At the start of the process, you load the dishwasher and add detergents to the appropriate compartments. Then you shut the machine, choose the wash cycle, and turn it on. After that, it’s the dishwasher’s turn. Every step in the dishwasher cycle happens in a specific order, and the machine monitors itself as the cycle proceeds.
Just Add Water
When you turn the machine on, the water intake valve opens to allow water into the basin at the bottom of the appliance. At the same time, the heating element heats the water to the appropriate temperature. The detergent is dispensed into the water, and the heat helps it dissolve and activate.
Dishwashers can reach temperatures of up to 155 degrees Fahrenheit — much hotter than the water heated by your hot water tank or tankless heating system. The higher heat helps food particles dissolve and kills bacteria to sanitize your dishes.
And… Spray!
Once the water hits the right temperature, hot soapy water pumps into the spray arms at the top and bottom of the machine. The high pressure of the jets on the spray arms forces the paddles to rotate, which helps ensure that water sprays over all the dirty dishes.
The water drips back into the basin at the bottom of the machine, along with food particles from the dirty dishes. Small particles wash away, but larger ones get trapped in the sieve or filter at the bottom of the basin so they don’t get into the spray arms and jam the machine.
Wash and Rinse
The cycle of heating water and pumping it up to the spray arms repeats until the end of the wash stage. The length of this cycle depends on the wash cycle chosen, but some modern dishwashers have sensors that can detect when dishes are clean.
At the end of this stage, the water drains into the basin one last time and gets pumped out of the dishwasher. Where the water goes next depends on the dishwasher hook-up. With most models, the water drains directly into the pipes under the sink. Other stand-alone older models drain the water into the sink directly.
Your dishwasher may also dispense rinse aids or go through separate rinse or sanitize cycles.
The Dry Cycle
Many modern dishwashers have an optional drying stage at the end of the wash cycle. This part of the cycle uses the heating element to heat the air inside the machine and help the clean dishes dry faster. Some people prefer to skip this stage and just let the dishes dry naturally. If you choose to use one of the heated, air-drying options, be careful not to select a dryer that is too hot, as it can melt lightweight plasticware.
Tips to Keep Your Dishwasher in Great Shape
Scrape Your Dishes
The dishwasher takes care of most of the work of cleaning dishes, but it’s still important to give the machine a helping hand! Before loading plates, pots, and pans, scrape them out to remove food scraps and heavy deposits of sauces. Over time, accumulated food deposits can clog the sieve or filter—and it’s much quicker and easier to scrape the plates than disassemble and clean out a clogged dishwasher.
Choose the Right Detergents
Use only dishwasher-formulated cleaning agents formulated to dissolve and activate in the high heat of a dishwasher. Soaps meant for handwashing dishes create large amounts of suds that can negatively affect the performance of your dishwasher. If you absolutely must use dish soap, add only two or three drops for a full dishwasher load.
Run the Hot Cycle
Modern dishwashers typically have an eco-friendly setting that runs the cycle at a lower temperature. The water is hot enough to dissolve food particles and clean the dishes but not necessarily hot enough to sanitize the inside of the machine. Bacteria can grow inside the machine, leading to unpleasant smells and the risk of contaminating clean dishes.
Luckily, it’s easy to prevent this problem. To do this, run your dishwasher on the hottest wash cycle around once every six months. For the best results, run it empty, and add half a cup of vinegar to the bottom of the basin before you start the cycle. The vinegar will help sanitize, freshen, and remove any lingering smells. Vinegar can also reduce scale build-up inside the appliance if your home water supply is hard.
Take Good Care of Your Dishwasher — It Pays Off!
Modern dishwashers are so efficient they actually use less water than you do when washing dishes by hand, so they’re a great way to clean and sanitize the dishes you use for cooking and eating.
Take good care of your dishwasher, and it’ll take good care of your dishes. When you need a helping hand, you can rely on CW Service Pros. Our expert plumbing professionals are on call for dishwasher repair and installation, should you be ready to install a new appliance for your home.