Excluding grommets, a hookah consists of a number of components, four of which are essential for its operation.
Also known as the head of the hookah, the bowl is a container, usually made out of clay, marble, or glass, that holds the coal and tobacco during the smoking session. The bowl is loaded with tobacco then covered in a small piece of perforated aluminum foil or a glass or metal screen. Lit coals are then placed on top, which allows the tobacco to heat to the proper temperature. There is also a variation of the head which employs a fruit rather than the traditional clay bowl. The fruit is hollowed out and perforated in order to achieve the same shape and system a clay bowl has, then it is loaded and used in the same manner. Bowls have evolved in recent years to incorporate new designs that keep juices in the tobacco from running down the stem. The Tangiers Phunnel Bowl and Sahara Smoke Vortex Bowl are two examples of such bowls.
Technically if the pipe has a hose it is not "hookah"—the term historically referred to a straight-neck tube. Today the hose (one or more) is a slender flexible tube that allows the smoke to be drawn for a distance, cooling down before inhalation. The end is typically fitted with a metal, wooden, or plastic mouthpiece of various shape, size, color or material type.
Many hookah are equipped with a purge valve connected to the airspace in the water jar to purge stale smoke which has been sitting unused in the jar for too long. This one-way valve is typically a simple ball bearing sitting over a port which seals the port by gravity alone and will open if positive pressure is created by blowing into the hose. The bearing will be held captive with a screw-on cover. The cover should be opened and the bearing and seat cleaned of residue and corrosion regularly to ensure proper sealing.
The body of the hookah sits on top of the water jar, or sometimes referred to as vase, or base. The downstem hangs down below the level of the water in the jar. Smoke passes through the body and out the downstem where it bubbles through the water. This cools and humidifies the smoke. Liquids such as fruit juice may be added to the water or used in substitution. Pieces of fruit, mint leaves, and crushed ice may be added. A plate, or ashtray, sits just below the bowl to catch ashes falling off the coals. Grommets in a hookah are usually placed between the bowl and the body, the body's gasket and the water jar and between the body and the hose. The grommets, although not essential (the use of paper or tape has become common), will help to seal the joints between the parts, therefore decreasing the amount of air coming in and maximizing the smoke breathed in.
A Hookah Cover windscreen is a cover which sits over the bowl area, with some form of air holes. This prevents wind from increasing the burn rate and temperature of the coal, and prevents ash and burning embers from being blown onto the surrounding environment. This may also offer some limited protection from fire as it may prevent the coal from being ejected if the hookah is bumped.
The jar at the bottom of the hookah is filled with water sufficient to submerge a few centimeters of the body tube, which is sealed tightly to it. Deeper water will only increase the inhalation force needed to use it. Tobacco is placed inside the bowl at the top of the hookah and then a foil or charcoal screen with a burning charcoal is placed on top. Some cultures cover the bowl with perforated tin foil or a metal screen to separate the coal and the tobacco, which minimizes inhalation of coal ash with the smoke. This may also reduce the temperature the tobacco is exposed to, in order to prevent burning the tobacco directly.
When one inhales through the hose, air is pulled through the charcoal and into the bowl holding the tobacco. The hot air, heated by the charcoal vaporizes (not burns) the tobacco, thus producing smoke, which is passed down through the body tube that extends into the water in the jar. It bubbles up through the water, losing heat, and fills the top part of the jar, to which the hose is attached. When a smoker inhales from the hose, smoke passes into the lungs, and the change in pressure in the jar pulls more air through the charcoal, continuing the process. If the hookah has been lit and smoked but has not been inhaled for an extended period, the smoke inside the water jar may be regarded as "stale" and undesirable. Stale smoke may be exhausted through the purge valve, if present. This one-way valve is opened by the positive pressure created from gently blowing into the hose. It will not function on a multiple-hose hookah unless all other hoses are plugged. Sometimes one-way valves are put in the hose sockets to avoid the need to manually plug hoses.