'Yes,' said Andy.
'Well, I know the harvester went around the septic tank, but why did it miss that bit by the hedge, too?'
Andy explained. According to our neighbour, Don, the liquid waste from our properties (waste water, pee) goes into the septic tank and then onwards into the bit by the hedge which is a sort of soakaway, and hence 'soaking away' into the earth. The remaining waste i.e poo (basically) is contained in the septic tank itself, and when that is full it needs emptying, about every two or three years or so.