Thread seal tape, or plumber's tape can be used in many ways, the most common use in America is to seal things. Thread seal tape — commonly known as "Plumber's tape", "PTFE tape", or "tape dope"is a polytetrafluoroethylene (PTFE) film cut to specified widths for use in sealing pipe threads. 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.
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Thread tape is appropriate for use on tapered threads, where it is the thread itself that provides the seal surface.[1] 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 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 of body piercings, 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, slowly increasing the size and thus slowly increasing the size (gauge) of the piercing.[2]
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 mils and a minimum PTFE purity of 99%.[3] The second standard, A-A-58092,[4] is a commercial grade which maintains the thickness requirement of MIL-T-27730A and adds a minimum density of 1.2 g/cc.[4] 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.[1]
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, green for oxygen, 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.
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 thread-seal 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 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.[5][6][7]