Isolated plumbing is specified where plumbing designers want to protect plumbing under isolated slabs (slabs over an under-floor space) from the damage that expansive soil can cause. Plumbing is isolated if the plumbing, hangers and supports below the slab are not in contact with the soil and not in contact with any assemblage of materials that is both in contact with the soil and plumbing, hangers or supports.
Learn more about why isolated plumbing is effectively required by current plumbing codes and why isolated plumbing will be explicitly required by the 2024 IPC in a new section of the code here.
Watch vidoes about Mudskipper Framing to isolate plumbing under slab-on-voidform foundations here.
Watch a video about Mudskipper Vaults which protect transitions of plumbing from isolated to non-isolated conditions at the perimeter of isolated slab foundations (slab-on-crawlspace and slab-on-voidform) here.