The gray water backs up in the kitchen sink when the washer drains or the water runs for an extended period.?

There is a separate gray water drainage line that doesn't have a tank between the house and the field. When the washer or dish washer drain the kitchen sink fills with the expelled water then slowly drains. I have snaked the drain and used a chemical drain cleaner-no improvement. I walked the line and noted that there are points along the line where water is seeping to the surface. Does the seeping indicate that the line may be crushed or clogged at those points? Would it be wise to reroute the line to the septic system?