If you have water from the waterjet tank going to drain, you will have suspended solids in this water (abrasive and small amounts of kerf material). To avoid the potential of clogging up sewer lines, this water should run through some sort of filter or weir tank to get as much suspended solids as possible out of the drain water. The filter could be as simple as a sock filter. Sock filters are available in various micron sizes. Something like a paper bed filter can have a roll of filter media that is continually advanced as the drain water passes through it.