How a Coffee Maker Works
 

How does a Coffee Maker work? A modern drip coffee maker is a surprisingly simple device. Manufacturers have had 25 years to hone their designs, so these coffee makers are pretty straightforward once you open them up.   If you take off the top of the coffee maker, you find three things: 1. There is a little bucket that holds the water when you pour it into the pot at the start of the coffee-making cycle (on the right in the picture above). There is a hole in the bottom of the bucket, and its role will become obvious in a moment. 2. There is a black tube that carries the hot water to the drip area. 3. There is the drip area. Water arrives here from the black hot-water tube and simply falls through the holes into the coffee grounds.     Looking at this picture, you get your first impression that this isn't a high-tech device. If you take the bottom off the coffee maker, here is what you will find: The depression on the right-hand side of this figure is the bottom of the bucket. The orange tube in the centre is the hot-water tube (it connects to the black tube that we saw in the previous picture). The other orange tube picks up cold water from the hole in the bucket. You can also see the power cord coming in as well as the switch that turns the coffee maker on and off.

View inside the top     View inside the bottom

You can see that a coffee maker is about as simple as an appliance can get!
Here's how it works:

1.
When you pour in cold water, it flows from the bucket through the hole in the bottom of the bucket and into the orange tube.

2.
The water then flows through the one-way valve into the aluminium tube in the heating element, and then partially up through the black tube. This all happens naturally because of gravity.

3.
When you turn on the switch, the heating element starts heating the aluminium tube, and eventually the water in the tube boils.

4.
When the water boils, the bubbles rise up in the black tube. What happens next is exactly what happens in a typical aquarium filter: The tube is small enough and the bubbles are big enough that a column of water can ride upward on top of the bubble.

5.
The water flows out the end of the black tube to drip into the coffee.
This boiling-water pump, by the way, is the same mechanism that drives a percolator-type coffee machine.

As you can see, there is no mechanical pump of any type and really no moving parts (except for the moving portion of the one-way valve). This makes coffee machines extremely reliable.