The question isn't really 'treatment plant or soakaway'- it should be 'treatment plant or septic tank'. Both solutions need to discharge the effluent somewhere, and the generally preferred method is a soakaway. You are allowed a 25% reduction in soakaway area if you use a treatment plant, but otherwise it's all much the same.   The reasons for not using a soakaway would be if you don't have enough space for one, or if the ground conditions are unsuitable (e.g. high water table, slow dr
    • Like
    1