Personally, I hate to bury supply pipes under concrete slabs, but I realize that it sometimes has to be done and there are standards that allow it to be done with a good chance that the job will last, at least for enough years that you are not likely to be held accountable for a leak… Copper and iron pipe should not be embedded in contact with cement, which will cause the pipe to corrode.There are various types of pipe wraps to keep the metal from contacting cement. I go a step further and cover the pipe with at least 6 mil of polyethelene vapor barrier film, and in any case I never embed the wrapped and covered pipe IN the slab. It goes BELOW the slab (and the slab reinforcement mesh or rebar). I also make sure to lay the pipe on a bed of sand and small sized smooth gravel over well tamped soil. You don’t want the slab to settle and crush the pipe.
In my opinion, the key to a trouble free under-slab system is to minimize fittings below slab…ideally you should have NO pipe fittings below the slab. This is best achieved by using flexible plastic pipe, such as polyethelene, or coiled copper pipe.
In all cases, make a very precise map of the underslab pipe runs. Keep a copy in your files and provide the homeowner with another. In the event that you need to break up the slab to repair a section of pipe, a precise map will allow you to do so with a minimum of demolition.