Buzz
This simple drip coffee machine may not come with an array of fancy features, but it can certainly deliver a fast cup of coffee. D3sign / Getty Images
For many caffeine lovers, breakfast is often accompanied by a reliable companion—the coffee machine. Each morning, you scoop the coffee grounds, add water, and switch it on. But have you ever paused to think about what’s happening inside? How does the water travel from the reservoir to the coffee grounds in the filter? How does it heat so efficiently, and what’s behind that distinctive gurgling sound?
In this article, we'll explore the inner workings of a typical drip coffee maker, helping you understand exactly what happens when you brew coffee. We'll also discuss some potential issues that could cause your coffee maker to malfunction. By the end, you might start seeing your old coffee companion in a whole new light.
Before diving into that, let’s quickly review some coffee basics. Coffee plants are evergreen tropical shrubs and small trees, thriving best between the Tropic of Cancer and the Tropic of Capricorn (also known as the Bean Belt). These plants love plenty of rainfall and moderate temperatures. The beans we use are actually the seeds of the coffee fruit, known as coffee cherries. These plants have been cultivated for centuries, and the two most common types are Coffee arabica (Arabica coffee) and Coffea canephora (Robusta coffee). For a deeper look into what's in your morning brew, check out the article How Coffee Works.
There are numerous coffee makers on the market that may offer a better cup of coffee, but in this article, we’ll focus on the dependable drip coffee maker. If your tastes lean towards something more sophisticated, take a look at the article How the Clover Coffee Maker Works. However, if you’re eager for an insider's peek at your kitchen’s appliance of the year, stick with us as we open it up and take a closer look in the next section.
Inside a Coffee Maker
Looking inside a drip coffee maker reveals that it’s actually quite a simple gadget.
Mytour 2008A modern drip coffee maker is a surprisingly straightforward machine. After more than 30 years of refinement, manufacturers have perfected the design, making these coffee makers simple and efficient once you take a look inside.
When you remove the top of the coffee maker, you’ll find three key components:
- There's a reservoir that holds the water when you pour it in at the start of the brewing process (seen on the right in the image above). There's a hole at the bottom of the reservoir, and its purpose will become clear soon.
- There's a white tube that rises from the bottom of the reservoir, carrying the heated water up to the drip area.
- On the left side of the image, you'll see a shower head. This is where water flows from the white tube, spraying over the coffee grounds. In some models, the water flows through a perforated plastic disk called the drip area and drips down onto the coffee grounds below.
At first glance, it’s clear that this isn’t a high-tech gadget. But if you remove the base of the coffee maker, here’s what you’ll discover:
Things are about to heat up!
Mytour 2008The indentation on the right side of this diagram represents the bottom of the container. The orange tube at the top draws in cold water from the hole in the reservoir. The orange tube at the bottom is the hot-water tube, connecting to the white tube we saw earlier. Additionally, the power cord is visible as well.
On the left side of the coffee maker’s base, you'll find the heating element. This component consists of an aluminum extrusion with two sections: a resistive heating element and a tube that allows water to flow through. Together, the heating element and the aluminum tube work to heat the water. On the next page, we’ll take a closer look at this setup.
The Heating Element of Coffee Makers
The heating element performs two key functions efficiently.
Mytour 2008The resistive heating element is essentially a coiled wire, resembling the filament in a light bulb or the element in an electric toaster, which heats up when electricity passes through it. In this resistive element, the coil is encased in a durable plaster for extra protection. The heating element serves two primary purposes:
- When you first add water to the coffee maker, the heating element activates to heat it.
- After the coffee is brewed, the heating element maintains the coffee’s temperature, keeping it warm.
In the image above, you can see how the resistive heating element is positioned between the warming plate and the aluminum water tube. The heating element presses directly against the underside of the warming plate, and white, heat-conductive grease ensures efficient heat transfer. This grease is incredibly messy (and hard to remove from your fingers!). It’s used in many devices, including stereo amplifiers, power supplies, and pretty much anything that needs to dissipate heat.
The coffee maker’s switch controls the power flow to the heating element. To prevent the heating element from overheating, there are additional components like sensors and fuses. The sensors monitor the coil’s temperature, cutting off the power if it gets too hot. Once it cools, the current is restored. This on/off cycling helps maintain a steady temperature. Fuses are safety features that cut power if the temperature exceeds a certain threshold, ensuring protection if the sensor fails.
The sensors and fuses of the coffee maker are likely located within the white sheathing that connects to the heating element.
Mytour 2008Another critical component of the coffee maker is the one-way valve. This valve is typically found either in the hole of the bucket or in the aluminum heating pipe. Without the one-way valve, boiling water could easily flow back into the bucket instead of rising up the white tube. The one-way valve allows cold water into the aluminum tube while forcing boiling water to flow upward. If you blow into the tube leading to the valve, it should open. If you suck air through the tube, the valve will block any air from passing through.
Now that we've covered the essentials, let's power up the coffee maker and give it a test run.
Making Coffee
Feeling sluggish? A cup of Mytour coffee is just what you need to jumpstart your day.
Mytour 2008All this coffee talk got you craving a cup? Here's how a drip coffee maker transforms a few spoonfuls of coffee grounds and some water into a fresh, hot cup of coffee.
As you can see, a coffee maker is one of the simplest appliances around. Here’s the breakdown of how it operates:
- When you pour cold water into the coffee maker, it travels from the reservoir through the hole and into the orange tube.
- The water then passes through the one-way valve, into the aluminum tube in the heating element, and rises partially up the white tube, all due to gravity.
- When you flip the switch, the resistive heating element warms the aluminum tube, eventually causing the water to boil.
- Once the water boils, bubbles begin to rise in the white tube. This process mirrors what happens in an aquarium filter: the tube's size and the bubble's volume create a column of water that moves upward with the bubbles.
- The water travels up the white tube, and is evenly dispersed over the coffee grounds.
- The hot water flows through the coffee grounds, extracting their oil essence as it moves into the pot. This coffee oil, released during roasting, is known as caffeol.
Sounds simple enough, right? This boiling-water mechanism is the same one used in percolator coffee machines. Notice there’s no mechanical pump or many moving parts (other than the one-way valve’s moving piece). This simplicity is what makes coffee machines so reliable.
Some drip coffee makers come with advanced features, giving you more control over your coffee brewing. On the next page, we’ll explore these features, and what happens when things go wrong and your coffee maker breaks down.
Drip Coffee Maker Problems: What Can Go Wrong with Your Coffee Maker?
You’re feeling groggy. The sky looks the same as when you went to sleep, and you drag yourself into the kitchen to flip that magical switch. But wait, what’s this? You turn it on and—nothing happens. No cheerful bubbling, no reassuring rumble. No coffee!
Here are some of the most frequent issues that could cause your drip coffee maker to malfunction:
- The power cord or on/off switch may fail. If this happens, it's safest to have a professional replace the faulty part or simply purchase a new coffee maker, as improper replacement could lead to a fire hazard.
- The one-way valve may become stuck, either open or closed. Usually, you can clear the obstruction with a toothpick.
- The tubes can accumulate calcium buildup. This is especially common in the aluminum heating tube. The typical solution is to run vinegar through the machine once, followed by two water cycles to flush out the vinegar.
Two issues are particularly difficult to resolve: failure of a heat-sensitive switch or failure of the heating coil. Since replacement parts for these are hard to come by, you'll most likely need to replace the entire coffee maker if either of these components fails.
Assuming your coffee maker is still in good working order, what advanced features might it have? For instance, many models come with a programmable timer, allowing you to set everything up the night before. When your alarm goes off, the coffee pot starts brewing, so by the time you stumble into the kitchen, your coffee is ready. Some models also include a built-in grinder, ensuring your coffee is freshly ground just before brewing. Another handy feature is the ability to pause the brewing process, allowing you to pour yourself a cup before the entire pot is done brewing, perfect for early risers who need their first cup before the rest of the house wakes up.
Many modern digital coffee makers also let you adjust the brew strength -- if you prefer a stronger cup, the brewing time slows to accommodate. Some even offer self-cleaning cycles and filtration systems. Freshness timers let you know how long your coffee has been sitting out, while automatic shut-off features ease any worries about forgetting to turn off the machine when you leave the house for work.
