The majority of the pipework in your house will probably be made of copper and in most cases it is best to use the same material when making additions or repairs. However, there are other options available to you.
Polybutylene pipe (also known as Hep2o pipe) can be used for both hot and cold water pipework and is ideal if the pipe run needs to make several curves or bends. It is easy to work with and can be cut with either a sharp knife or pipe cutters. It is usually sold in a roll, but can also be bought in long straight lengths. Polybutylene pipe insulates well but cannot be used for very high temperature water and cannot be directly connected to a boiler. On long runs it will need to be supported to avoid sagging.
Cross-cut polyethylene pipe (or PEX pipe) is simillar to polybutylene pipe in that it is easily bent around corners or obstacles and can be used for both hot and cold pipework. It can be painted and insulates well, meaning that it can be used in areas where it will be seen. It is joined with push-fit or compression joints (if a pipe insert is used) and can be cut with a sharp knife. Due to the material, it will need to be supported over long runs and cannot be used to link directly to a boiler.
Copper pipe is by far the most common type of pipe found in UK homes. It can be used for both hot and cold pipe runs, and can be connected directly to a boiler. Copper pipe is available in three sizes: 15, 22 and 28mm, and is sold in saveral different lengths. You will need to use a pipe bender or elbow joints for taking the pipe around corners, but it is relatively easy to work with and various push-fit (speed-fit) joints are available. Copper pipe will only require support over very long lengths (although this varies depending on the thickness of pipe being used). The downside of using copper pipe is that it insulates badly and can split if allowed to freeze, but even these problems can be avoided with some cheap and widely available pipe insulation. Copper pipe needs to be cut with a hacksaw or a pipe cutter.
Stainless Steel Pipe
Using stainless steel pipe is much the same as using copper pipe, but can be connected to galvanised steel pipe without the risk of a corrosive reaction. Stainless steel pipe is much more expensive than copper pipe, and can be harder to work with. Stainless steel pipe is only really used where the pipe is exposed and made into a design feature.
No longer available, but can still be found in some older houses. Lead pipe should be replaced with copper or plastic pipe as soon as possible due to the risk of the lead contaminating the water supply.
Safe Pipe Runs
Any copper (or other metal) pipe runs must be connected to the main earth bonding system to avoid the chance of someone touching exposed pipe and being electrocuted if the pipe somehow becomes live. If you have added a section of plastic pipe into an earthed copper run, you need to bridge the gap with a length of bridging wire. If you are unsure about earthing copper pipe, speak to a qualified electrician or plumber.
Copper pipe is available in three sizes; 15, 22 and 28mm. The size is measured by the outside diameter, so make sure you buy the correct size if joining new pipework to old. Very old pipework may be imperial sizes and an adaptor will need to be used to connect it to new copper pipe. Plastic pipes are available in the same diameters, but the walls of the pipe are usually thicker than copper for added strength.