In moving our kitchen to another part of the house, I discovered (after removing the old floor cabinets) that the plumbing seems rather "unusual". The 3/4" lines comes out of the floor (slab) to go up to the old sink, but then cross over above the slab about a foot before then going down again under the slab to the washing machine about 12 feet away. Since that will now be a living room, I have to get these pipes below the slab. To do that I will have to remove concrete, then join the copper pipes together before replacing the concrete. That will put copper joints below the slab. I don't see any other way to do this, but I don't like having joints under the slab. Having not done this before, am I being too concerned about having these joints under the slab? My skills with soldering copper are pretty good.