The Whitworth thread, also called pipe thread, is mainly used in gas and water installation. The parameter here is the inside diameter of a threaded pipe, measured in inches. Since threaded pipes can have different wall thicknesses, the reference to the inside diameter is very confusing. Here is an example: A 1 inch pipe thread does not have an outside diameter of 25.4 mm but about 32.89 mm to 33.25 mm, depending on the wall thickness of the thread pipe.
Pipe Thread Sealing cord or sealing tape.