The next time you visit a DIY store or builders merchant, stop in at the plumbing section and take a look at the huge range and variety of small plumbing fittings that are available. Brass, copper, plastic, chrome – all are available in a confusing array of different sizes. But what do they do, and how do they work?
The generic name for these products is copper fittings. This term refers to the fact that they are used in conjunction with copper pipe (or a substitute product such as plastic) in the supply of hot and cold water or central heating. Copper fittings do indeed come in a number of different shapes and sizes, but they are generally classified into four groups. These groups are derived from the actual method that is adopted when the fitting is put into use.
The first group is known as solder ring fittings. Solder ring fittings (sometimes referred to as Yorkshire fittings) are made of either copper or brass. The fitting itself contains a small ring of cooled solder around the circumference of the inside of the fitting. When the copper pipe is pushed into the fitting and flux (a cleaning and activating paste) is applied along with intense heat, the solder melts and runs around the joint, cooling and solidifying once more as soon as the heat source is removed, forming a solid joint.
The second type group of fittings are known as end feed fittings. These fittings are almost identical to solder ring fittings except that they do not contain an integral ring of solder – when using end feed fittings the solder is supplied by the plumber from a reel or solder stick. When the pipe / fitting joint is at the correct temperature, the plumber offers the tip of the solder reel or stick up to the joint. The intense heat melts the solder, which is then "drawn" or "fed" into and around the fitting by capillary action. Once more the joint is made when the heat is removed and the solder sets. These fittings are favoured by plumbers as they are considerably less expensive than solder ring fittings, and equally efficient when used correctly.
The third group of fittings goes by the name of compression. These are generally brass fittings that use a mechanical pressure joint method sometimes referred to as "nut and olive". The olive is a thin band of either copper or brass that is shaped like a wedding ring and which, along with a threaded nut, fits over the copper pipe, the pipe is then inserted into the fitting, and the female thread on the nut is tightened down onto the male thread on the body of the fitting. As the nut is tightened, the olive is crushed down onto the pipe and into concave seat inside the fitting, making a secure and watertight joint. Some plumbers favour the use of a proprietary pipe jointing compound around the olive when using compression fittings.
The final and newest group of fittings is called push fit fittings. Cleverly designed using internal grab rings, they are used in conjunction with technically advanced flexible plastic pipes supplied in either coils or lengths. Small metal or rigid plastic pipe stiffeners are inserted into the end bore of the pipe, ensuring that the wall of the pipe does not distort under pressure. The pipe is then inserted into the fitting until it reaches the integral stops inside the fitting, ensuring that the grab rings are located in the correct position. The joint then reaches its full strength when pressurised by the water flowing through it.
Regardless of which of the four groups the fittings belong to, they are always sized in reference to the diameter of the copper pipe that they are used to join. The most common sizes in domestic plumbing applications are 15mm, 22mm and 28mm.