Types of Pipe and Pipe Joints

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.

Capillary Joints

These joints are soldered: the small space between the pipe and the 'sleeve' is filled with molten solder which solidifies and holds the joint together in a watertight seal. There are two types of capillary joints: in an end feed joint, solder is introduced into the mouth of the end feed joint and flows by capillary action into the fitting; the integral ring fitting already contains solder in a reservoir or 'ring'.

Pipe Bends, or Elbows

The direction of a copper pipe can be changed by bending it. Sometimes bends or elbows are used to join two pipes at 45 degrees or 90 degrees. At the lesser angle, the joint may be a capillary joint, but at 90 degrees, the joint will be a compression joint. A wrench is used to tighten a cap nut, and a ring of soft metal called an 'olive' is compressed to fill the joint between the fitting and pipe.

Pipe Joints

As well as bends or elbows, capillary and compression joints are used to connect pipes at various angles and in different combinations. Typical examples are straight connectors (for joining pipes in a straight line); tees (to join three pipes); and adaptors (to join pipes of different materials such as copper to galvanized steel, and to join new metric pipes to old imperial-sized ones).

Pipe Fittings

Fittings are jointing systems used for connecting pipes, such as the bib tap. Other fittings in domestic plumbing include tank connectors (for joining pipes to cisterns); tap connectors (for joining a supply pipe to a tap or faucet); drain cocks (to empty pipes); and gate valves (a hand-operated on-off valve).

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