Hello As explained by the friend Servimat (greetings !!) the heating pipe is placed in the subfloor, NOT in the slab itself, therefore you can place 6 or 8 fisher plugs without any problem. It is called "radiant slab" but in fact it is "radiant floor", before if the plumbing pipes were embedded in the slabs; but this system was left to be used by the various problems that embed a metal pipe with temperature in a concrete slab brings (cracks, cracks, etc ...) Regards !