I've had 3 blocked drain episodes in the past 8 mos. This last one I asked them to bring along a camera thinking it possibly was tree roots. We have a slab foundation home; I was advised that there was a "belly" in the piping that ran the 54 ft underneath the slab to the main clean out behind the house and that water and etc. was collecting there. The plumber stated it w/b advisable to trench below the slab, replace the current pipes and add hangers to the under side of the foundation every 4 ft. This project was going to cost $24,000. The second plumber I called advised me to trench along the side of the house breaking out the driveway and back patio concrete to reach the main clean out. They would "seal" off the old drains from the kitchen sink, laundry room and 1/2 bath tying into the new drainage outside. I have a wet bar over the "belly" that uses the current drain; I'm concerned as to how it w/b affected, and additionally, about disturbing the packed soil beneath the slab foundation as minor subsidence has occurred along a few streets in our subdivision. How does a "belly" develop beneath a slab foundation if there's no water leaks, We've had no recognizable increase in our water bill for the past 10 yrs? Thx for your thoughts on this dilemma.