About hoppers
The scale of your soakaway needs to be no less than 1m x 1m sq. x 1m deep below the bottom with the incoming pipe. The stone infill should surround the pipe and finish approximately 100mm higher than it. An impervious layer ought to then be put on the stone such as thick polythene, tarpaulin, or even a bed of concrete (A1 while in the diagram highe