Final answer:
Section 312.2 indeed prohibits direct embedment of hubless cast-iron pipe in concrete; this ensures inspection and repair access and accounts for pipe movement.
Step-by-step explanation:
The statement that Section 312.2 prohibits the direct embedment of hubless cast-iron pipe in a concrete slab is True. According to various plumbing and building codes, cast-iron piping without a hub, known as hubless piping, usually requires support by using hangers or by resting on a firm foundation and not by being directly embedded in concrete. This is to ensure that the pipe can be properly inspected and if needed, repaired or replaced without having to break the concrete. It also allows for some movement due to thermal expansion or contraction and prevents damage to the pipe that could be caused by the concrete.