For hundreds of years, the traditional material for drains has been short lengths of salt-glazed clay pipes (the glazing helped make the clay watertight). Originally, the joints were made by packing a gasket of tarred hemp into the gap between the spigot end of one pipe and the socket of its neighbour and filling the rest of the gap with clay. The joints were flexible and were liable to give a little as the pipeline settled as a result of ground movement.
But these joints tended to leak, so they were superseded by a cement filling (still with a tarred rope gasket to prevent the cement from falling into the pipeline before it dried). In fact, the whole pipeline was usually bedded on a cement base, with the cement carried up the sides of the pipe.
But a pipeline like this is often too brittle, and can break if ground settlement takes place. Modern practice is often to revert to the original idea of flexible joints and indeed flexible beds and flexible pipes.
The main materials used for house drains are clay, pitch fibre and PVC.
Clay
Modern clay pipes are not always salt-glazed (they are more impervious than they used to be). Socket pipes are still used, but the sockets and spigots usually have plastic linings and are sealed with a rubber 'O'-ring. Plain-ended pipes are also available: these are jointed with a plastic sleeve which slips over both pipe ends; again, sealing rings seal the joint. A large range of clay fittings is available, and pipes still come in short lengths. It usually takes a bit of practice to cut them successfully they have to be cut with a sharp bolster chisel in the same way as bricks: filling the pipe with sand may help to prevent it breaking in the wrong place.
Pitch fibre
These pipes are made from waste paper and other fibres soaked in pitch. For drainage work, the pipes usually come with plain ends and are jointed with a plastic sleeve. The sealing rings used are called snap rings - as the sleeve is pushed into place over the pipe, the ring should suddenly and clearly snap into place. The joints will remain watertight even if the completed pipeline is not dead straight. There is a range of plastic fittings- including ones for jointing pitch fibre to other materials.
PVC
These are joined in the same way as plastic waste pipes either by using sockets or sleeves with sealing rings or by solvent welding. A range of fittings is available, including ready-made inspection chamber bases, rodding points, gullies, and fittings to join PVC to other materials. PVC pipes come in even longer lengths than pitch fibre but can also be cut easily.
