Blockages within a drain pipe can be a sign of a more serious issue and usually it isn't until you have a drainage problem which could be a blocked Drain a bad smell from your drain, a flooded or overflowing manhole or a sewerage leak that the root cause of the problem can be inspected and identified. In some cases a one off blockage may be a result of items being flushed into the se not further investigated after clearance often leading to another clearance visit.