How do I know if my drains/sewers are blocked?

If the drain or private becomes blocked it may cause waste water/sewage to overflow from manhole covers or drainage gulleys outside, or cause toilets and sinks to empty too slowly. You may be able to smell sewage either inside your house or outside. Sometimes with a private sewer which is carrying waste water away from a number of properties a neighbour who is located closer to the blockage may know there is a problem before you do.