What would have caused the blockage or damage?
It is not always possible to find out. Sometimes things are found in the pipework which may have caused a blockage, such as disposable nappies or excessive quantities of congealed grease, but it is seldom possible to prove that they were the primary cause. A blockage can be caused by something as small as a cotton bud, razor blade or matchstick getting lodged in a joint and trapping other material behind it. Sometimes more serious foreign objects such as pieces of wood, brick or cement are found and must be removed to prevent them causing further obstructions. Some lengths of pipework have inherent faults which lead to frequent blockages but may be impossible to repair economically. For instance inadequate falls causing sluggish flows or minor settlement of some of the pipes causing small steps at the joints which obstruct the flow. Few drains remain in perfect condition – open joints and slightly displaced pipes are common but do not necessarily cause problems. Many older drains have
