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| superseded by a cement filling (still with a tarred rope | | | | fibres soaked in pitch.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