(British type-A/non-manipulative) and flare fittings (British type-B/manipulative). Standard fittings require no modifications to the tubing. Flare fittings require modification of the tubing with a special tool. Standard fittings are typically used for water, hydraulic and compressed air connections, whereas flare fittings are used for gas and high pressure lines. A standard fitting can be installed using an ordinary wrench to tighten the surrounding nut. To remove it, a specialized puller is often used to slide the nut and ferrule off the tube. If the ferrule is difficult to remove it can be weakened with a cut, care being taken to not nick the pipe while cutting. Advantages Compression fittings are popular because they do not require soldering, so they are comparatively quick and easy to use. They require no special tools or skills to operate. They work at higher pressures and with toxic gases. Compression fittings are especially useful in installations that may require occasional disassembly or partial removal for maintenance etc., since these connections can be broken and remade without affecting the integrity of the joint. They are also used in situations where a heat source, in particular a soldering torch, is prohibited, or where it is difficult to remove remains of water from inside the pipe which prevent the pipe heating up to allow soldering. Disadvantages Compression fittings are not as robust as soldered fittings. They are typically used in applications where the fitting will not be disturbed and not subjected to flexing or bending. A soldered joint is highly tolerant of flexing and bending (such as when pipes knock or shake from sudden pressure changes e.g. caused by water hammer). Compression fittings are much more sensitive to these type of dynamic stresses. They are also bulkier, and may be considered less aesthetically pleasing than a neatly soldered joint. Compression fittings work best when tightened once and not disturbed. Some compression connectors may never be reused, such as a ferrule ring type. It can never be reused once they have been compressed. This connector is directly placed over the pipe and the nut is tightened compressing the ferrule between the pipe and the body of the fitting. Compression of this ferrule also results in deformation of the copper tubing. If a compression type connection needs to be redone, more often than not the compressed copper/ferrule would need to be cut off and a new ferrule is to be