Many different materials have been used over the years for domestic pipe-work, so you may find various combinations of pipe materials in your home. While lead is no longer used for modern plumbing, many homes still have a lead rising main. This is fine, but any other lead plumbing should be replaced. Cast iron was most often used for soil pipes, and when these have rusted through they are generally replaced by plastic versions. Copper tubing is probably the most extensively used material: lightweight, easy to solder and bend, it can be used for both hot and cold water supplies. Three sizes are used in domestic plumbing: 15mm (1/2in), 22mm (3/4in) and 28mm (1in). Brass is used to make compression joints, taps, and stopcocks. Plastic pipes are a recent introduction and as yet, unstandardized, but they are cheap, lightweight, do not freeze or corrode, or affect other materials (copper joined to galvanized steel and brass to copper produce an electro-chemical action which causes corrosion), and depending on the types, can be used for both hot and cold water systems.
While copper pipes can be bent, with plastic pipes pre-shaped sections have to be inserted. It is necessary to use a 'fitting' in the following situations: when two lengths of pipe have to be joined in a straight line; to allow the introduction of a branch connection; to allow for a change of direction; to control the flow of water; and to release air and drain off water. There are three types of fitting: straight coupling; bent coupling or elbow; and branch fitting, and there are two types of pipe connectors: compression joints and capillary joints.
