A blocked drain will make itself know, firstly by smell, followed  by overflowing from the ORG grate on the side of your house.  Blocked drains usually occur because tree roots have entered the drain pipe or foreign matter i.e. kids toys, toilet rim freshner or sanitary items have been flushed down the toilet and are causing a blockage.  Fat from kitchen sinks is also a common item which causes drains to block.

To fix blocked drains we use a drainage machine which operates by feeding a rod cutter into the drain to remove the obstruction.  We then test the drain the ensure the blockage has passed.  

Unfortunately there are no means of preventing tree roots from re-entering the drain however you can control what items are put down your sink drain and flushed down your toilet to prevent blockages.