Threaded joints is a technology that has been designed to join piping systems by coupling thread ended pipes and accessories available as male thread and female thread connector types and selection of thread standards to choose from e.g.: BSP, NPT or G. Threaded joints are mainly used on smaller diameters pipes in non-critical applications such as domestic oil, gas, air conditioning, heating & ventilation installations but can also be seen pneumatic, automotive applications. Threaded fittings are usually made of bronze, brass plastic or cast iron. The most common types of threaded fittings are 90° elbows, 45° elbows, tees, straight fittings, square head plugs, hex head plugs, reducers, adaptors, flanges, caps, bushings. Threaded fittings systems ensure leak-tight connections in all low-pressure, low-temperature installations where vibration is not encountered.
DZ or DZR symbol stamped on brass components means that the part is dezincification resistant. Dezincification is a form of corrosion that can occur within a plumbing and heating system.
To measure the size of male fittings you need to calculate the OD (outside diameter) of the pipe. However, to measure female fittings you need to measure ID (inside diameter) of the pipe.
Stuck brass, copper or bronze threaded fittings can be loosened in two ways. Firstly, you need to shut off the supply and scrub away a crusty residue on the outside of the fitting. Once it's done, try using penetration liquid directly on fittings thread and leave it for a while. If it doesn't work, try heating the fitting as the metal expands when heated. An expanded metal will break the sticky residue and let the fitting to move.
It is always recommended to use some kind of sealing with threaded fittings, no matter if it's a BSPP, BSPT, NPT or any other type of thread. This could be a gasket, washer, sealing tape or sealing liquid.