Thread Seal Tape
Combining a Watertight Seal with an Anti-Seize Solution
Thread sealing tape, also known as plumber's tape and teflon tape, is typically used on tapered threads to prevent galling during fastening while also providing a more secure, watertight seal for the application. In some ways, thread sealing plumber's tape functions very similarly to anti-seize solutions such as MRO, with the added bonus of making the fastener watertight.
Thread Seal Tape works by lubricating the fastener, allowing for a deeper seating of the threads to help prevent the threads from seizing. The tape also functions like a deformable filler, helping to seal the fastener without hardening or making it more difficult to tighten.
Typically thread seal tape is used by wrapping it around the threading a few times before fastening. Plumber's tape is most effective on tapered threads where the sealing force is a wedge action. Parallel threads may not seal effectively with or without tape. In this case it is better to use a gasket.