I've decided to break open the new slab again. It seems like such a shame, and the same time, matters little, since the whole thing will be covered. This is some of the hardest concrete I've had to break. My neighbour next door called us, because he felt the banging of the sledgehammer in his living room! I started off by drilling holes, it seemed like the drill lacked it usual get up and go. After drilling half a dozen holes, I realized the drill was in reverse. It took about 2 hours to get to this point, the hole needs to be a little longer, that'll be easier, now that I can dig under the slab though. It rather a tricky part of the plumbing, there' the vent for the toilet, the sink and the shower all coming together in one place, it's a bit of a puzzle to figure it all out.