Faucet, Mixer, Tap, Filler - Where These Terms Come From

Faucet

A "faucet" is basically a plumbing device that controls the flow of water from a reservoir or water source. The term is commonly used in the US and faucets can be found in kitchens, bathrooms, and other industrial applications. Kitchen faucets are also typically known to be bigger and more luxurious in appearance than bathroom faucets. In the UK or Europe, it's more common to see the term "mixer".

Mixer or Mixer Tap

The term "mixer" refers to a device that also regulates the flow of water, just like a faucet. The origin of the word mixer comes from the fact that the device is controlling the flow of the hot water and cold water simultaneously. This mixing functionality is what allows the user to control the temperature of the water coming out by mixing the hot and cold water to their desired preference. The term mixer or mixer tap is more commonly used in the UK and Europe.

Tap

The word "tap" is short for "mixer tap". In the US, the word tap is used but not in reference to the mixer but rather the water that comes out. It's very common for Americans to say "tap water" in reference to the water that comes out from the faucet. A tap can also refer to valves that release substances other than water. You might find "gas taps" in a chemistry lab or "beer taps" at a bar.

Filler or Pot Filler or Tub Filler

A "pot filler" is a faucet that's mounted over your stove. Because this "filler" is mounted over your stove, and not over a sink, you can't use it to wash your hands or run water down the drain--there is none. Pot fillers are used purely for cooking purposes and filling large cooking pots with water. This saves you a lot of time while cooking because you don't have to spend time and energy carrying many big pots back and forth to the sink. You will find pot fillers in many commercial kitchens and just recently, they are now becoming quite popular in homes. Generally, most pot fillers are only connected to the cold water line. More expensive models will offer mixing functionalities since they connect to both the cold and hot water lines.

A "tub filler" is basically the mixer valve that fill your bathtub with water. I wouldn't necessarily call it a faucet because it isn't shaped like one (it's more like just a spout and handles) but it basically does the same thing.

Faucets/Mixers VS Fillers

The key difference between fillers VS faucets/mixers is that fillers are meant to dispense water very quickly. Fillers are often very simply in appearance and don't have any filters or anything impeding the flow of water. When you're cooking or trying to relax in your tub, you definitely don't want to stand there all day while the water comes out in a slow drip. Fillers are meant to fill your pot or tub as fast as possible.

In contrast, faucets and mixer taps are used much more often for a wider variety of applications and so they have more attributes to them. For one, faucets and mixer taps are part of the kitchen and overall home design so they are usually more elegant and decorative in appearance. Faucets and mixer taps are also used more often and so there is usually a filter or aerator that restricts their flow to save water usage over time. Another thing is that faucets and mixers used to fill containers with water, other times they may be used as a spray hose for cleaning. Because of this wide variation in features, they have may have attachable heads and different filters that allow the water to come out in different shaped streams and flow. They are much more than just simple hot & cold water mixing valves!