Thread seal tape, or teflon tape can be used in many ways, the most common use in America is to seal things. Thread seal tape — commonly known as "Teflon tape", "PTFE tape", "tape dope", or "plumber's

Plumbing

Plumbing is the system of pipes and drains installed in a building for the distribution of potable drinking water and the removal of waterborne wastes, and the skilled trade of working with pipes, tubing and plumbing fixtures in such systems. A plumber is someone who installs or repairs piping...

 tape"–is a polytetrafluoroethylene

Polytetrafluoroethylene

Polytetrafluoroethylene is a synthetic fluoropolymer of tetrafluoroethylene that finds numerous applications. PTFE is most well known by the DuPont brand name Teflon....

 (PTFE) film cut to specified widths for use in sealing pipe threads

Threaded pipe

A threaded pipe is a pipe with screw-threaded ends for assembly.- Tapered threads :The threaded pipes used in some plumbing installations for the delivery of gases or fluids under pressure have a threaded section that is slightly conical . This is called a "tapered thread"...

. The tape is wrapped around the exposed threads of a pipe before it is screwed into place. The tape is commonly used commercially in pressurized water systems, such as central heating systems, as well as in air compression equipment and thread joints with coarse threads. One of the defining characteristics of PTFE is how good it is at defeating friction. The use of PTFE tape in tapered pipe threads performs a lubricating function, which more easily allows the threads to be screwed together, to the point of deformation, which is what creates the seal.

Uses

Thread tape is appropriate for use on tapered threads, where it is the thread itself that provides the seal surface. It is not required on parallel threads; parallel threads will not seal effectively themselves, even with tape. The sealing force on a tapered thread comes about from wedge action, that of a parallel thread is merely the axial force from the nut and is inadequate for a good seal. For this reason parallel threads are only used to mechanically clamp some other form of seal (e.g. a metallic pipe olive, or a flat face with a conformable washer

Gasket

thumb|sright|250px|Some seals and gaskets1. [[o-ring]]2. fiber [[Washer |washer]]3. paper gaskets4. [[cylinder head]] [[head gasket|gasket]]...

 against it). These seals do not require additional tape, and applying tape to their threads has no purpose.
PTFE tape is also commonly used in the stretching

Stretching (body piercing)

Stretching, in the context of body piercing, is the deliberate expansion of a healed fistula for the purpose of wearing body piercing jewelry. Ear piercings are the most commonly stretched piercings, with nasal septum piercings, tongue piercings and lip piercings/lip plates following close behind...

 of body piercing

Body piercing

Body piercing, a form of body modification, is the practice of puncturing or cutting a part of the human body, creating an opening in which jewelry may be worn. The word piercing can refer to the act or practice of body piercing, or to an opening in the body created by this act or practice...

s, through a process known as taping, because it is inert and safe for this use. The wearer wraps layers of the tape around a plug

Plug (jewellery)

A plug , in the context of body modification, is a short, cylindrical piece of jewellery commonly worn in larger-gauge body piercings. Because of their size—which is often substantially thicker than a standard wire earring—plugs can be made out of almost any material...

, slowly increasing the size and thus slowly increasing the size (gauge

American wire gauge

American wire gauge , also known as the Brown & Sharpe wire gauge, is a standardized wire gauge system used since 1857 predominantly in the United States and Canada for the diameters of round, solid, nonferrous, electrically conducting wire...

) of the piercing.

Types

There are two US standards for determining the quality of any PTFE tape. MIL-T-27730A (an obsolete military specification still commonly used in industry in the US) requires a minimum thickness of 3.5 mil

Thou (unit of length)

A thou also known as a mil or point, is the verbalized abbreviation for "thousandth of an inch." It is a unit of length equal to 0.001 inch....

s and a minimum PTFE purity of 99%. The second standard, A-A-58092, is a commercial grade which maintains the thickness requirement of MIL-T-27730A and adds a minimum density of 1.2 g/cc. Relevant standards may vary between industries; tape for gas fittings (to UK gas regulations) is required to be thicker than that for water. Although PTFE itself is suitable for use with high-pressure oxygen, the grade of tape must also be known to be free from grease.

Thread seal tape is most commonly a white film (the natural color of PTFE) and is used in plumbing applications, but it is also available in various colors. While pigmented thread seal tape is not materially different from the natural white tape, it is often used to correspond to color coded pipelines ((US, Canada, Australia & New Zealand) yellow for natural gas

Natural gas

Natural gas is a naturally occurring gas mixture consisting primarily of methane, typically with 0–20% higher hydrocarbons . It is found associated with other hydrocarbon fuel, in coal beds, as methane clathrates, and is an important fuel source and a major feedstock for fertilizers.Most natural...

, green for oxygen

Oxygen

Oxygen is the element with atomic number 8 and represented by the symbol O. Its name derives from the Greek roots ὀξύς and -γενής , because at the time of naming, it was mistakenly thought that all acids required oxygen in their composition...

, etc.). These color-codes for thread sealing tape were introduced by Bill Bentley of Unasco Pty Ltd in the 1970s. In the UK, tape is used from coloured reels, e.g. yellow reels for gas, green for potable water.

Hazards

Over-use, or mis-application of thread tape may be a hazard. An excess amount of tape can prevent mating threads from fully engaging, therefore reducing the shear point of the threads. The use of teflon tape in addition to a pipe dope compound can also be dangerous, because it can become too much between the flanks of the threads. As the tape material is so soft, excess or overhangs may easily break off and form a foreign body contaminant that could jam a valve seat

Valve seat

The valve seat in an internal combustion gasoline or diesel engine is the surface against which an intake or an exhaust valve rests during the portion of the engine operating cycle when that valve is closed...

etc.

Thread sealing tape is almost entirely applied by hand, owing to the ad hoc nature of most repair work, although at least one machine is available for production wrapping of fittings.