Our kitchen drain in our old farmhouse drains slowly and I have noticed that the ground above the drain/pipe area outside becomes mushy when we do dishes. I realize our drain pipes may be collapsed or blocked. However, I heard that kitchen drains have a grease trap that may need to bee cleaned out periodically. Is this situation symptomatic of this problem as well? Would you suggest digging out this area to check it out? Any other info on grease traps?