You need to look at the size of the septic tank and what it can take as inflow. If it cannot handle the inflow of waste-water, a 100% closed loop system with a DI unit and chiller will be needed. Under these circumstances, and we have units running like this, no water goes down the drain at all and all cutting water is used again for cutting. Make-up water is needed, as some water will be lost to evaporation etc.