Pitch fibre drainage pipes were introduced in the 1940s and were used extensively until the 1970s. They were thought at the time to be the latest wonder material, being cheaper than fired clay pipes, and also lightweight and easy to handle. They were made from wood fibre impregnated with coal tar.
They performed adequately when dealing with normal wastewater, however, they have been found to react badly when subjected to large quantities of hot water, oils and fats which can soften the tar and cause deformation and leaks. The design life of pitch fibre pipes has been estimated at 40 years, meaning that most have reached the end of their life expectancy. In severe cases they can collapse, blocking the drain run.