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A tap (also spigot or faucet: see usage variations) is a valve controlling the release of a liquid or gas.
Nomenclature
In the UK and most of the Commonwealth of Nations, taps are used for any everyday type of valve, especially for fittings controlling the water supply to baths and sinks.
Tap is the most common term in the United States, similar to "tap" in British English, eg "water tap" (although the term "tap" is also used in the United States).
Spigot is used by industry professionals such as plumbers and usually refers to outdoor fixtures.
Silcock (and sillcock), synonymous with "tap", refers to a "cock" that penetrates the foundation (eg stopcock and petcock).
Taps (faucets and hose taps or hose taps), usually a freeze-proof version of the "tap".
Wall hydrant, same as "hosebibb".
A faucet usually refers to a keg or barrel faucet, but also usually refers to a faucet that supplies either hot or cold water, but not both.It also appears in the descriptor for "tap water" (i.e. water purified for domestic use).Single-temperature faucets are commonly found in commercial or public restrooms, where the water temperature will be controlled by a separate thermostatic valve that mixes hot and cold water.Regulating valves may be located under the treatment sink or in a separate mechanical room or service room.These single-serve faucets are less prone to failure from heavy use or vandalism.
Liquid
Water for baths, sinks and washbasins may be provided by separate hot and cold taps; this arrangement is common in older facilities,especially in communal washrooms/lavatories and utility/laundry rooms.In kitchens and bathrooms, thermostatic taps are often used. In this case, hot and cold water from two valves mix before reaching the outlet, allowing water to flow at any temperature between the hot and cold water supplies.The mixer tap was invented and patented in 1880 by Thomas Campbell of St. John's.For baths and showers, thermostatic faucets usually have some kind of pressure equalization feature, so the hot and cold mix ratio is not affected by momentary changes in the pressure of one water source or another.This helps avoid scalding or uncomfortable cold during other water loads such as flushing the toilet.Mixer faucets typically use a single, more complex valve controlled by a single handle (single-handle mixer),rather than two separate valves.The handle moves up and down to control water flow, and left and right to control water temperature.Especially for baths and showers, the latest design is the thermostatic mixing valve, which uses a built-in thermostat to do this, which can be mechanical or electronic.There are also faucets with colored LEDs that show the water temperature.If separate taps are installed, it may not be immediately clear which tap is hot and which is cold.
Hot water faucets usually have a red indicator, while cold water faucets usually have a blue or green indicator. Faucets are also often marked with an "H" or "C". In Romance languages, the letters "C" for hot and "F" for cold are used (from French "chaud"/Italian "caldo"/Spanish "caliente" (hot) and French "froid"/Italian" freddo” / Spanish “frio” (cold)). Portuguese uses Q (for "quente", hot) and F.This can confuse English-speaking visitors. Mixer faucets may have red and blue stripes or arrows to indicate which side will get hot and which will get cold.In most countries there is a standard hot/cold water tap arrangement.For example, in the United States and many other countries, building codes require that hot water taps be on the left side. Many installations ignore this standard (plumbers call it a "cross-connect"). Incorrect assembly of some single-valve mixer taps can cause heat and cold to swap, even if the unit is properly plumbed.Most household handles are screwed onto the valve shaft, but in many commercial and industrial applications they incorporate a removable key, known as a "loose key", "water key", or "tap key", which There is a square peg and a square key to turn the water off and on; the "loose key" can be removed to prevent vandals from turning the water on.Before the "loose key" was invented, some landlord or janitor would usually remove the handle of the faucet, where the teeth of the faucet met the gear on the valve shaft. Most modern faucets still use this system of teeth and cogs. "Loose keys" may also be found outside homes to prevent passers-by from using them.Faucets are usually connected to the water supply with a "swivel faucet connector" that attaches to the end of the water pipe using a weld or compression fitting and has a large nut that screws onto the threaded "tail" of the faucet, which hangs from the tub, face under a basin or sink.Use a fiber gasket between the connector and the tail of the tap (it expands when wet to help seal).Faucet ends are usually 1⁄2" or 12 mm in diameter for sinks and 3⁄4" or 19 mm in diameter for bathtubs, although continental Europe sometimes uses the 3⁄8" (still imperial) size.Same connection method For bathtub cue.The term tap is widely used to describe a valve used to dispense draft beer from a keg, either gravity-fed or pressurized.
Gas
A gas tap is a special form of ball valve used in residential, commercial and laboratory applications for the coarse control of the release of fuel gases such as natural gas, coal gas and syngas.Like all ball valves, its handle is parallel to the gas line when open and perpendicular to the gas line when closed, allowing for easy visual identification of its status.
Mechanisms
In 1845, Rotherham brass founders Guest and Chrimes patented and manufactured the first screw-in tap mechanism. Most older faucets use a soft rubber or neoprene washer that is screwed onto the valve seat to stop the flow. This is known in engineering as a "globe valve" and while it provides a leak-tight seal and fine flow fine-tuning, both the rubber gasket and seat wear (and, in the case of the seat, corrode) over time, so Eventually a tight seal was not formed in the closed position, causing the faucet to leak. Gaskets can be replaced, seats can be resurfaced (at least a few times), but globe valves are never maintenance free.In addition, the water is forced to follow a tortuous S-shaped path, which creates a significant resistance to flow.For high-pressure domestic water systems this is irrelevant, but for low-pressure systems where flow is important, such as a shower fed by a storage tank, a "globe valve" or in engineering terms a "gate valve" is preferred.Gate valves use a metal wedge with a rounded surface, usually the same diameter as the pipe, that is screwed into place perpendicular to the flow of water, shutting it off.There is very little resistance to water flow when the faucet is fully open, but this type of faucet rarely provides a perfect seal when closed.In the UK, this type of tap usually has a wheel handle rather than a cane or winch handle.Cone or ball valves are another option.These usually appear as service shut-off valves in more expensive water systems, usually in gas taps (by the way, the keg beer taps mentioned above).They can be identified by the range of motion (only 90°) between fully open and closed.
Typically, the valve opens when the handle is in line with the pipe and closes when the handle passes through the pipe.But it can move in the CW or CCW direction perpendicular to the pipe. S=off, O=open.Cone valves consist of a shallow tapered cone seated in a tight-fitting socket across fluid flow. In British English this is often called a tapered cock.Ball valves use spherical balls instead.In either case, the hole through the cone or sphere allows fluid to pass if the cone or sphere is aligned with the opening in which the fluid enters and exits in the receptacle; turning the cone with the handle rotates the passageway so that the fluid appears in the cone On the intact surface of the body, it cannot pass through. Sometimes you come across valves that use a cylinder instead of a cone, but using a cone allows for a tight fit even with moderate manufacturing tolerances.
In a ball valve the ball rotates within a plastic (usually Teflon) seat.Hands-free infrared proximity sensors are replacing standard valves.Thermostatically controlled electronic dual-purpose mixing or diverting valves are used in industrial applications to automatically supply liquids on demand.Foot operated valves are installed in laboratory and healthcare/hospital, as well as industrial environments where extremely dirty hand operated faucets may leave residue on them.Modern faucets often have aerators at the tip to restrict water flow and introduce air in the form of bubbles to reduce splashing. Without an aerator, the water will usually come out of the faucet in one big stream. Aerators disperse the water flow into many small droplets. In hygienic environments such as hospitals or laboratories, "laminar flow units" are used in place of aerators. Laminar flow restricts water flow and directs water into a smooth stream without introducing ambient air that may contain harmful bacteria or particles. Modern bathroom and kitchen faucets often use ceramic or plastic surfaces to glide against other spring-loaded ceramic surfaces or plastic washers. These taps take advantage of the uniquely low coefficient of friction values of the 2 ceramic surfaces in contact, especially with water as the lubricant. These faucets tend to require far less maintenance than traditional globe valves, and when maintenance is required, the entire interior of the valve is usually replaced, often as a pre-assembled cartridge., uses a rubber seat facing the cartridge. Each design has its advantages: Moen elements tend to be the easiest to find, American Standard elements have virtually unlimited life in sediment-free municipal water, and rubber seats tend to be the most tolerant of sediment in well water.
