If there's an inspection pit outside lift the cover and see if there's any depth of foul water in there. I have to do this every few months.
If there is a blockage, the outflow will be at the bottom and will point towards the road. I unblock with a 6 foot length of plastic water pipe (barrier pipe) which has the right stiffness and is also flexible enough to bend into the outflow pipe.
Try to pull any paper debris back into the pit to begin with and then try to push the obstruction clear. Clean up with a garden hosepipe - it takes me ten minutes now and the smell no longer bothers me.
Good luck...
Peccavi, May 2009
