In the past drainage companies used drainage rods to push a blockage through the pipe. Although these rods are still used from time to time, they have been superseded by drain jetting equipment.
In the drain jetting process, water at a pressure of 3,000PSI is directed into the drain. The force of the water is enough to break up any clogs within the pipe into small components, which can then be flushed through the drainage system.
Some tough blockages may need to be rodded to forcibly move the blockage through the sewer network. However, because the water jet produced by drain jetting is at such a high pressure, rodding is becoming more uncommon.
In newer types of drain jetting, the jet tube is pushed into the sewer until it reaches the blockage site. This means that when the water supply is turned on, the water jet is only centimetres away from the clog so maximum pressure and hence maximum dispersion can be achieved.
Many drain blockages in London can be cleared quite effectively using the water jetting process, however, when jetting alone fails to shift a stubborn clog, the London drainage company may insist on a CCTV survey so the reason for the clog can be found.